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\DOI{10.5802/crgeos.227}
\datereceived{2023-03-02}
\daterevised{2023-06-24}
\dateaccepted{2023-06-26}
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\dateposted{2023-07-27}
\begin{document}

\begin{noXML}

%\makeatletter
%\def\TITREspecial{\relax}
%\def\cdr@specialtitle@english{Tribute to Jean Dercourt}
%\def\cdr@specialtitle@french{Hommage \`a Jean Dercourt}
%\makeatother

\title{The Middle to Late Triassic of Central Saudi Arabia with
emphasis on the Jilh Formation. Part II: sequence stratigraphy,
depositional and structural history, correlations and paleogeography}

\author{\firstname{Yves-Michel} \lastname{Le Nindre}\IsCorresp}
\address{Geo-consultant (BRGM retired), 58 Rue Gustave Flaubert 45100,
Orl\'{e}ans, France}
\email[Y.-M. Le Nindre]{yc.lenindre@wanadoo.fr}

\author{\firstname{Roger Brett} \lastname{Davies}}
\address{Davies Geoconsulting (retired), Wintergreen House, Queen's
Road, Harrogate, North~Yorkshire, HG2 0HB, UK}
\email[R. B. Davies]{davies.geoconsulting@btinternet.com}

\author{\firstname{Benoit} \lastname{Issautier}}
\address{BRGM, 3, Avenue Claude Guillemin, B.P. 36009, 45060,
Orl\'{e}ans Cedex 2, France} 
\email[B. Issautier]{b.issautier@brgm.fr}

\author{\firstname{Leopold} \lastname{Krystyn}}
\address{Dept. of Palaeontology (Geozentrum), University of
Vienna, Althanstrasse 14, Josef-Holaubek-Platz 2 (UZA II) 1090 Vienna
(retired), Austria}
\email[L. Krystyn]{leopold.krystyn@univie.ac.at}

\author{\firstname{Denis} \lastname{Vaslet}}
\address{Geo-consultant (BRGM retired), 275 Route Royale, 33240 La
Lande de Pomerol, France}
\email[D. Vaslet]{d-d.vaslet@wanadoo.fr}

\author{\firstname{Bruno} \lastname{Vrielynck}}
\address{Institut des Sciences de la Terre de Paris (UMR 7193),
Universit\'{e} Pierre et Marie Curie (UPMC) (retired), France}
\email{bruno.vrielynck@orange.fr}
\email[B. Vrielynck]{bjm.vrielynck@orange.fr} 

\author{\firstname{Abdullah} \lastname{Memesh}}
\address{Saudi Geological Survey, 54141, Ahmed bin Mohammed Al Ashab
St., Jeddah 21514, Saudi Arabia}
\email[A. Memesh]{Memesh.AM@sgs.gov.sa}

\shortrunauthors

\keywords{\kwd{Saudi Arabia}
\kwd{Triassic}
\kwd{Jilh Formation}
\kwd{Minjur Sandstone} 
\kwd{Sequence stratigraphy}
\kwd{Correlations}
\kwd{Paleogeography}}

\begin{abstract}
New biostratigraphic data reported by Le Nindre et al. (2023 -- this volume)
improve the sequence stratigraphic
understanding of the Middle--Late Triassic mixed
carbonate-silicilclastic Jilh Formation and overlying siliciclastic
Minjur Formation at outcrop in Central Saudi Arabia. The Anisian Tr40,
Ladinian Tr50, Julian Tr60, Tuvalian Tr70 and Alaunian Tr80 MFS are all
identified and their ages discussed. A major Carnian--Norian hiatus
(Tr80 SB) approximates to but notably cuts across the mapped
Jilh--Minjur Formation boundary. A younger Late Norian--Rhaetian
transgression (Tr90 MFS?) is also identified. All of these major
transgressive--regressive sequences and hiatuses can be identified with
confidence and correlated at the regional scale with time-equivalent
carbonates. The ages of subsurface lithostratigraphic units identified
elsewhere across the Arabian Plate, notably the ``Jilh, Sefidar and
Marker Dolomites'', ``Jilh Evaporite'' (sometimes ``Carnian Salinity
Crisis'') and the \textit{incertae sedis} Baluti Formation, and their
equivalence in the Saudi Arabian outcrops, are assessed in the light of
these results. The presence of significant siliciclastics at the base
of the Carnian stratigraphy (``Julian Clastic Event'') is also
discussed.

Ladinian conodont faunas belonging to the Sephardic Province (Iberia,
North Africa) and associated vertebrate faunas confirm transgression
from the north. Similar conclusions are drawn for the Carnian and
Norian transgressions.

The improved geochronologic understanding enabled a reconstruction of
the structural phases of the Jilh geohistory in four steps from Anisian
to Norian, showing the relationships of retrogradation--progradation
processes and tectonic pulses to hiatuses and periods of erosion. A
synthetic sequence stratigraphy is proposed.
\end{abstract}


\maketitle

\twocolumngrid

\end{noXML}

\section{Introduction}

This study is the second part of an updated reconstruction of the
sedimentary complex formed by the Jilh Formation and the overlying
Minjur Sandstone (Middle and Late Triassic) in Saudi Arabia and
adjacent countries, principally, but not exclusively, from outcrop
data. It builds on a factual litho- and biostratigraphic base set up in
Part I \citep{LeNindreetal2023}, which the reader
should refer to, in a first stage. 




Part I of this study (this volume), provided updated and detailed
descriptions of the litho- and biostratigraphy of the Middle to Late
Triassic Jilh Formation and Minjur Sandstone along a 50~km-wide outcrop
belt extending between latitudes 28\textdegree~N and 21\textdegree~N,
along the eastern margin of the Arabian Shield (Figure~\ref{fig1}). Together
with the Permian--Early Triassic Khuff Formation and the Early Triassic
Sudair Shale, these formations form an unconformable cover over the
Pre-Permian rocks, and are in turn unconformably overlain by Jurassic
and younger formations  \citep{Powersetal1966,Powers1968}.
\citet{LeNindreetal1987,LeNindreetal1990b} published a revised
description of the lithostratigraphy, biostratigraphy and sedimentology
of the Permian--Triassic at outcrop, based on the results of the cover
rock geological mapping program at 1:250,000 scale by the Directorate
Mineral Resources of Saudi Arabia (DMMR) and France's Geological
Survey (BRGM). More recent publications provide a detailed description
and interpretation of the underlying Khuff Formation 
\citep[e.g.][]{Vachardetal2005,Vasletetal2005} and overlying Minjur Sandstone
\citep[][Figure~\ref{fig2}]{Issautieretal2012a,Issautieretal2012b,Issautieretal2019}.

\begin{figure*}
\vspace*{-3pt}
\includegraphics{fig01}
\vspace*{-3pt}
\caption{\label{fig1}Simplified geological map of the Arabian Peninsula showing the
quadrangles in which the Jilh Formation crops out. These quadrangles in
Central Saudi Arabia were mapped by the DMMR (now Saudi Geological
Survey) and France's BRGM (Hawasina nappes in Oman not shown, Qatar
Arch from \citealp{Stewartetal2016}; in green, wells and transects cited in
the text).}
\vspace*{-3pt}
\end{figure*}

\begin{figure*}
\vspace*{-3pt}
\includegraphics{fig02}
\vspace*{-3pt}
\caption{\label{fig2}The Khashm al Khalta (K. al Minjur) promontory, type locality
of the Minjur Sandstone, capped by the Marrat Formation, and the Lower
Dhruma Formation; (c. 23\textdegree 35$'$~N, 46\textdegree 09$'$~E, Ar Rayn
quadrangle). The foreground corresponds to the base of the Formation.
The isolated hill of sandstone was interpreted as a flow tidal sand
ridge [Sequence 2, \citealp{Issautieretal2012a}]. See Figure~\ref{fig3} for
sequences and MFS interpretation in relation with the Jilh Formation.
Photo Y. M. Le Nindre, Nov. 2008.}
\vspace*{-4pt}
\end{figure*}

Key results of Part I were provided by new analyses of conodonts, and a
revision of previous ammonoids identifications, including a new
specimen collected in 2016. In particular Part I identified an Early
Norian hiatus of more than 10~Ma within the upper Jilh Formation
accompanied by marine and fluvial erosion.

Most of the Arabian Plate suffers from poor biostratigraphic age
control during the Triassic. It is only in a few sections near the
margins of the Arabian Plate or outcrops such as those described in
Part I that have yielded good faunal or floral evidence. This
emphasises the importance of new biostratigraphic data from the Central
Saudi Arabian outcrops (documented in Part I, this volume) to
understanding the more regional picture.

This Part II describes the internal organization of the
transgressive--regressive (T--R) depositional sequences in the Jilh
Formation and Minjur Sandstone based on precise dating by conodonts and
ammonoids. Comparisons are made to regional maximum flooding events.
From this point, reference to stages and substages, palynozones,
sequences and maximum floodings is preferred to lithological units.
Building on this, it is possible to reconstruct the tectonic and
depositional history of the Jilh Formation and provide an overall
sequence stratigraphic framework for the Middle to Late Triassic
outcrops. Applying this knowledge to published sections of the Jilh
Formation in the Central Ghawar area and eastwards into the eastern Rub
al Khali Bains \citep{DevilledePeriereetal2022} demonstrates
the applicability of the scheme at a regional scale. By including new
data on Minjur Sandstone stratigraphy \citep{Issautieretal2019},
this analysis provides a correlation tool for the entire Middle to Late
Triassic stratigraphy, extending from the outcrops to subsurface
sections at the platform scale regardless of lateral facies changes.

Biogeographic and paleogeographic considerations demonstrate the
northerly provenance of transgressions in the Middle to Late Triassic
setting. An~updated chronostratigraphic chart of the Permian to Mid
Toarcian sedimentation includes these new results and summarizes the
overall time evolution of the depositional systems. 

\section{Geometry and ages of the depositional sequences}\label{sec2}


Accounting for both the system tracts geometry, obtained by mapping
lithology and paleo-environments, and the ages of the main marine
intervals obtained from conodont and ammonite biostratigraphy in Part
I, it is now possible to combine the two in order to reconstruct
isochronous depositional sequences (Figure~\ref{fig5}). This exercise
demonstrates the importance of combining age and sequence \mbox{stratigraphy}
to reconstruct a correct and reliable geometry, based on genetic
criteria. It faithfully reflects the depositional mechanisms, beyond
the apparent lithostratigraphy, as seen section after section over more
than 880~km. The results highlight structural processes, erosional
surfaces and unconformities, as discussed below  (Figures~\ref{fig6}a--d
and~\ref{fig7}).


\subsection{Maximum flooding intervals and surfaces}

There is limited consensus on sequence stratigraphic schemes for the
Triassic of the Arabian Plate, mainly due to the sparsity of
biostratigraphic control. The~most widely cited scheme, 
\citeauthor{Sharlandetal2001}'s \citeyearpar{Sharlandetal2001} sequence
stratigraphic model for the Middle to Late Triassic was based to a
large degree on the succession in Iraq but subsequent publications
demonstrate that it was misapplied over the southern half of the
Arabian Plate including Saudi Arabia, particularly in their
interpretation that the Anisian is missing. This led to a re-evaluation
of Triassic sequence stratigraphy by a number of\break authors.


In this study, the maximum flooding surface nomenclature (MFS,
Table~\ref{tab1}) is adapted from 
\citet{Sharlandetal2001,Sharlandetal2004} as revised by 
\citet{DaviesSimmons2018}, as their scheme has the best match with the
new age data and stratigraphic organisation identified in the current
study. \citet{DaviesSimmons2018} proposed new reference sections for
both MFS and SB on the Arabian Plate that had the best published
biostratigraphic control. These tended to be in outcrops either towards
the margins of the Arabian Plate, or along the Saudi Arabian outcrop
where a fuller range of faunas and floras had been investigated and
thus dating was better defined 
\citep[e.g.,][]{LeNindreetal1990b,LeNindreetal2023}.

\begin{table*}[t!]
\fontsize{8.5}{10}\selectfont
\tabcolsep=3pt
\caption{Tentative numerical ages (Ma) Triassic MFS on the Arabian shelf\label{tab1}}
\begin{tabular}{ccccccccc}
\thead
\parbox[t]{1.5cm}{\centering Surface  (this study)} &
\parbox[t]{1.5cm}{\centering \citet{Sharlandetal2001} and GTS 96} & 
\parbox[t]{1.5cm}{\centering \citet{HaqAlQahtani2005} and GTS 2004} &
\parbox[t]{1.5cm}{\centering \citet{DaviesSimmons2018} GTS~2020} & 
\parbox[t]{1.5cm}{\centering This study  GTS 2020-03} &
\parbox[t]{1.5cm}{\centering Sequence  \citep{OggChen2020}} & 
\parbox[t]{1.5cm}{\centering Sequence  \citep{Haq2018}} & Age (Ma) &
\parbox[t]{1.3cm}{\centering Max sea  level (Ma)} \vspace*{4pt}\\
\endthead
Triassic/Jurassic \vspace*{6pt} &  &  &  & 201.4 & &  & 201.36 &  \\
\parbox{2cm}{\centering Mid Norian  MFS Tr80} \vspace*{6pt} &  215 & 
211.0 & \parbox{1.5cm}{\centering Late Norian  $c.$ 213} &  217.0 & 
TNo3? &  TNo3? &  222.5--217.3 &  ? \\  

\parbox{1.5cm}{\centering Tuvalian  MFS Tr70} \vspace*{6pt} &  222 & 
220.0 &  \parbox{1.5cm}{\centering Tuvalian  $c.$ 230} &  230.0 &  TCar2
&  TCa2 &  233.5--229.0 &  230 \\  

\parbox{2cm}{\centering Latest Julian  MFS Tr60} \vspace*{6pt} &  226 &
226.0 &  \parbox{1.5cm}{\centering Julian  $c.$ 234.7} &  234.0 &  TCar1
&  TCa1 &  236.2--233.5 &  234.5 \\

\parbox{2cm}{\centering Late Ladinian  MFS Tr50} \vspace*{6pt} &   233
&   234.0 &  \parbox{1.5cm}{\centering E. Ladinian  $c.$ 241} &  239.0 &
TLad2 &   TLa2  &  239.5--238.0 &   238.5 \\

\parbox{1.5cm}{\centering Anisian  MFS Tr40} \vspace*{6pt} &  238 & 
241.0 &  \parbox{1.5cm}{\centering Pelsonian  $c.$ 243.8} &  242.5 & 
TAn3 &  TAn3 &  243.5--242.1 &  242.5 \\

\parbox{1.5cm}{\centering Olenekian  MFS Tr30} \vspace*{4pt} &  245 & 
249.8 &  \parbox{1.5cm}{\centering Smithian  $c.$ 249} &  248.5 &  TIn3
&  TIn3 &  250.0--247.9 &  248.5 
\botline
\end{tabular}
\end{table*}


These MFS are positioned in our marine intervals (MFI) in outcrop
(Figure~\ref{fig5}) on the basis of the most commonly accepted ages of
the surfaces, irrespective of the original sections taken for
definition, which mostly suffer from poor or negligible
biostratigraphic control (Table~\ref{tab1}). The main marine
surfaces/intervals containing fauna dated in Part I
\citep{LeNindreetal2023} are MFS/MFI Tr40 (Anisian),
Tr50 (Ladinian), Tr60 (Early Carnian), Tr70 (Late Carnian), and Tr80
(Norian). Then, the biostratigraphic ages of the surfaces have been
refined according to the accuracy of the latest biostratigraphic
results from outcrop. It is noteworthy that
\citet{DevilledePeriereetal2022}, using palynology, also identify four
sequences with comparable ages in the Jilh Formation of the eastern Rub
al Khali Basin. 


Numerical ages in the Triassic are poorly constrained with most stage
boundaries only provisionally dated with few formal Global Boundary\unskip\break
Stratotype Section and Points [GSSPs, nine for the Triassic in 
\citealp{OggChen2020}]. Thanks to the contribution of Moujahed
Al-Husseini, we have tentatively assigned numerical ages to the
successive MFS on the Arabian shelf by using the International
Chronostratigraphic Chart v2015/01 [\citealp{Cohenetal2013}, updated; 
\citealp{Ogg2012,Ogg2015}], and the software TimeScale Creator, version
6.4, February 2015. The age model for Version 6.4 is from ``The
Geologic Time Scale 2012'' \citep{Gradsteinetal2012}, and the Triassic
scale is by \citet{Ogg2012}.


The latest International Chronostratigraphic Chart 2022/10 
\citep[][updated]{Cohenetal2013} shows only very minor changes (on base
Induan and top Rhaetian) from the 2015-01 version. Those changes do not
materially affect our interpretations. The ages are the following: Base
Induan: 251.9~Ma (252.17 in version 2015-01); Induan--Olenekian: 251.2;
Olenekian--Anisian: 247.2; Anisian--Ladinian: 242; Ladinian--Carnian: 237;
Carnian--Norian: 227; Norian--Rhaetian: 208.5; Rhaetian--Hettangian:
$201.4 \pm 0.2$.\looseness=-1

\subsubsection{Maximum flooding surface MFS Tr30 and MFS Tr40}

\paragraph{MFS Tr30}

In this study we do not address the Early Triassic (mid-Scythian) MFS
Tr30 of \citet{Sharlandetal2001,Sharlandetal2004} but for the sake of
completeness, we briefly mention it here. They picked MFS Tr30 within
the upper Sudair Formation \citep{Sharief1986}, and dated it 245~Ma in
GTS 1996.  \citet{HaqAlQahtani2005} followed Sharland et~al.\ by also
picking MFS Tr30 in the Sudair Shale and revised its age to 249.75~Ma
in the Olenekian (upper Scythian) in GTS 2004. More recently, 
\citet{DaviesSimmons2018} have updated the plate-wide correlation of
the Triassic T--R sequences in coordination with this study. In Saudi
Arabia, MFS Tr30 was picked in the Sudair Shale in a bioclastic
arenitic dolomite with marine fauna at 187~m in the SHD-1 Well 
[\citealp{Manivitetal1985b}, Darm\={a} quadrangle] and suggested to be
of probable Early Olenekian (Smithian) age. The best candidate in the 
\citet{Haq2018} and \citet{OggChen2020} schemes would be in their
sequence TIn3. \citet{Daviesetal2019} identified strong diachroneity
between siliciclastics of the Sudair and lower Jilh Formations and the
carbonates and evaporites of the Dashtak Formation on opposite sides of
the Arabian Gulf.


\paragraph{MFS Tr40}

\citet{Sharlandetal2001} interpreted Anisian MFS Tr40 in the Arabian
Plate and dated it 238~Ma according to GTS 1996, but had not identified
it in Saudi Arabia or neighbouring countries. \citet{HaqAlQahtani2005}
revised the numerical age to 241~Ma in GTS 2004 and followed Sharland
et~al.\ in assuming it is missing due to a hiatus in the Anisian. While
the Anisian age for MFS Tr40 remains valid, the numerical age
assignments are clearly outmoded due to updates to the time scale. In
\citet{DaviesSimmons2018}, a Mid-Anisian (Pelsonian) age of the MFS
Tr40 is demonstrated by the presence of ammonoids of the Balatonicus
zone in the Tethyan domain, and supported by the presence of the
conodont \textit{Nicoraella kockeli}, in carbonate beds of the Ra'af
Formation (Negev southern Israel) taken as reference section.\looseness=-1


Here we assign MFS Tr40 to the tidal and infralittoral bioclastic
dolomite slab forming the first cuesta of the Jilh Formation at the
outcrop from which the SHD-1 Well was drilled. An equivalent horizon
can be followed at the outcrop scale. This interpretation matches that
of \citet{DaviesSimmons2018} which was undertaken in concert with one
of the authors (YML). \looseness=-1


Given this biostratigraphic age, the MFS Tr40 best corresponds to
sequence TAn2, from 244.24 (SB) to 243.33~Ma (TAn3 SB) and maximum sea
level at 244~Ma in \citet{Haq2018} and \citet{OggChen2020}, GSSP,
adopted here.


\subsubsection{Maximum flooding surface MFS Tr50}

\citet{Sharlandetal2001} dated MFS Tr50 at 233~Ma in the Ladinian and
tentatively positioned it in the Jilh Formation in Saudi Arabia
\citep{Sharief1986,VickersRichetal1999}. \citet{HaqAlQahtani2005}
revised the numerical age to 234~Ma in GTS 2004, and picked it in the
Ladinian part of the lower Jilh Formation. The Ladinian age remains
valid but the numerical age has changed due to timescale updates.
\citet{DaviesSimmons2018} assigned it to ``thin dolomite beds
containing the conodont \mbox{\textit{Pseudofurnishius murcianus}}
immediately below the J1/J2 boundary in the Jilh Formation 
reference section at outcrop
\citep{LeNindreetal1990b}''.



In our study two marine episodes appear during the Ladinian, the first
one characterised by \textit{Budurovignathus truempyi}, and the
second one by \textit{B. mungoensis}. They both occur in the upper
part of Unit J1. The first marine event is characterized by the
association \textit{P. shagami}, \textit{P. murcianus} and
\textit{B. truempyi}. In one hypothesis, it thus would correspond to
the mid--late Fassanian transgressive cycle TLad1 of GSSP 2020 
\citep{OggChen2020}. 


However, we interpret that the major MFS is defined instead by the
southward extent of the \textit{P.~murcianus}--\textit{B.
mungoensis}, association of Late Ladinian (Longobardian) age, as
explained in Part I. In fact, \textit{Budurovignathus} appears
associated with flooding events, and is recovered from the dolomitic
benches, representing more offshore (deeper?) settings, whereas
\textit{Pseudofurnishius} is associated with the clastic regressive
phase above, or more proximal (shallower?) settings. This hypothesis is
supported by the vertical distribution of the conodonts where the two
are present, and by restriction of \textit{Budurovignathus} to a
more marine area (lat. 24\textdegree 27$'$~N--26\textdegree 21$'$~N).


In the chart of \citet{Haq2018}, this time interval corresponds to a
transgressive cycle TLa2 from 239.5 (SB) to 238~Ma (TLa3 SB), spanning
the Longobardicum and Neumayri ammonite zones---early--mid 
Longobardian---with the maximum sea level at 238.5~Ma. The same is
recorded in  \citet{OggChen2020}. This major carbonate marine event is
recognized and dated all along the outcrop from Khashm Dolqan
(24\textdegree 15$'$~N) northward. 


\subsubsection{Maximum flooding surface MFS Tr60}


\citet{Sharlandetal2001} picked MFS Tr60 in the Jilh Formation in Saudi
Arabia \citep{Sharief1986,VickersRichetal1999} and dated it at 226~Ma
in the Carnian. \citet{HaqAlQahtani2005} also estimated its age as
226~Ma, and similarly picked it in the Carnian part of the lower Jilh
Formation. Referring to \citet{Haq2018}, it best corresponds to the
sequence TCa1 from 236.2 (SB) to 233.5~Ma (TCa2 SB), with the maximum
eustatic sea level at 234.5~Ma. 


In our study, Late Triassic, latest Julian (Early Carnian) MFS Tr60
occurs in mapped Unit J2, or mapped Unit J3 respectively north and
south of 25\textdegree~N. It is the major maximum flooding interval (MFI)
of the Jilh Formation, as shown by the more transgressive facies, while
the major clastic influx at the base of this sequence occurred in early
Julian. This transgressive event reached up to Jabal al Arid
(23\textdegree 31$'$~N) where the~dolomite on top of the Unit J3 contains
\textit{Quadralella polygnathiformis} (Carnian) with the
southernmost marker of Julian, \textit{P. inclinata}, at Khabra
Halwah (23\textdegree 55$'$~N) just beneath the pre-Minjur  unconformity.


\citet{DaviesSimmons2018}, placed Tr60 in dolomitic beds bearing
\textit{Quadralella polygnathiformis} on top of the Unit J3 of the
Khashm Dolqan reference section. Although these beds correctly
represent the MFI, in fact the key markers 
(\textit{P. inclinata}---Julian---and \textit{Q.
polygnathiformis}---Carnian \textit{s.l.}) were provided by the
neighbouring section of Khabra Halwah (VD80-328, 329) as explained
above, and not by the reference section. 


The numerical age of the Julian/Tuvalian boundary is not adequately
constrained in GTS 2015 and may be about 233.6~Ma 
\citep{Ogg2015,OggChen2020}. \citet{Furinetal2006} reported a
\tsup{206}Pb/\tsup{238}U age of 230.91~Ma $\pm$ 0.33~Ma for zircons
from an ash bed within the range of the conodont
\textit{Metapolygnathus nodosus} in the middle--upper Tuvalian. These
age estimates imply latest Julian MFS Tr60 is no younger than 230.9~Ma
and probably older than 233.5~Ma, or about 8~Ma older than previous
estimates. We attribute an approximate age of about 234.0~Ma for latest
Julian MFS Tr60.



\subsubsection{Maximum flooding surface MFS Tr70}


\citet{Sharlandetal2001} did not identify MFS Tr70 in Saudi Arabia.
Based on undated outcrop data from Iraq they estimated its age as 
222~Ma, while \citet{HaqAlQahtani2005} estimated its numerical age as
220~Ma, both in the Late Carnian, and showed it in the Carnian part of
the upper Jilh Formation. \citet{DaviesSimmons2018} had identified it,
based of work by one of the authors (YML), interpreting its age as Late
Carnian on the ammonoid ``\textit{Clydonites} sp.,'' identification
of which was reinterpreted in Part~I. They also noted the presence of
the conodont \textit{P.~inclinata} in the reference section. In fact,
\textit{P. inclinata} was found on top of a neighbouring section\unskip\break 
(VD80-328, 329, Khabra Halwah), and is a fossil marker of the  Julian.


In our study, Tuvalian (Late Carnian) is identified in Unit J3,
principally north of 25\textdegree~N. The development of marine
carbonates in the north with Tropitids and conodonts identifies this
flooding event. The presence of the conodont \textit{Quadralella
carpathica} points to the early to middle Tuvalian, while Tuvalian 1 up
to Tuvalian 2/I is indicated by the Tropitid ammonoids. A common
associate is \textit{Q. polygnathiformis}.


With a Carnian--Norian boundary at 227~Ma (ICC 2020/03 and 2022/10) and
the base of Tuvalian at 233.6~Ma, an age of 230.91 $\pm$ 0.33~Ma in
middle--upper Tuvalian is correct. Thus, we estimate the numerical age
of MFS Tr70 around 230~Ma. This MFS best corresponds to sequence TCar2
in \citet{OggChen2020} from 233.6~Ma (SB) to 228~Ma (TCar3 SB), with a
maximum sea level at 230~Ma. 


\subsubsection{Maximum flooding surface MFS Tr80}


In the literature, definitions and assignations of MFS Tr80 are
uncertain and multiple, principally due to lack of reliable
biostratigraphic or numerical ages. Furthermore, the Norian period was
characterised by the broad extent of continental areas and sedimentary
hiatuses \citep{DaviesSimmons2018,Maureretal2008,Maureretal2015}. This
situation {engendered} {subsequent} confusing and conflicting
interpretations.



\citet{Sharlandetal2001} assigned a Norian age to MFS Tr80 (215~Ma,
i.e., mid Norian in the time scale of 1996)  but age diagnostic
fossils were lacking at the time of writing (apart from potentially
Norian pollens in Kuwait). They did not identify Tr80 in Saudi Arabia
although the surface was tentatively picked in neighbouring Kuwait and
Abu Dhabi. Sharland et~al.\ proposed a reference section near the base
of the Sarki Formation in Iraq, although they acknowledged the absence
of biostratigraphic age control. If the age of the Lower Sarki
Formation is Norian  \citep{Hanna2007,Lunnetal2019}, Sharland et~al.'s
interpretation that the ``Marker Dolomite'' of Lunn et~al.\ near the top
of the Kurra Chine Formation, equivalent to the Sefidar Dolomite, near
the top of the Dashtak Formation in Iran, also contains MFS Tr80 cannot
be correct. The Baluti Formation separates the underlying ``Marker
Dolomite'' from the overlying Sarki Formation \citep{Lunnetal2019}.
Palynological data confirms that at least part (but not necessarily
all) of the Baluti\unskip\break Formation is Late Carnian [only composite samples
were analysed---\citealp{Lunnetal2019}], thereby confirming that the
``Marker Dolomite'' is also of Carnian age. The Sefidar Dolomite
corresponds, by the underlying lithologic succession
(dolomite--evaporite--dolomite) and by its wire line characteristic
response to the ``Marker Dolomite'', elsewhere named ``Jilh Dolomite''
in Saudi Arabia. This equivalence is best demonstrated by the presence
of the distinctive Jilh Dolomite in offshore gas fields, notably Karan,
that lie adjacent to the median line with Iran \citep{Sodagar2015}.
This unit is assigned herein to the Early Carnian MFS Tr60 [see further
paragraph~4.2 on ``Jilh Dolomite'' and \citealp{DaviesSimmons2018}]. 


As noted previously, \citet{Sharlandetal2004} placed the MFS Tr80 in
the early Middle Norian: from this point of view, it would correspond
to our Alaunian 1 transgression dated in Part I.
\citeauthor{HaqAlQahtani2005} [\citeyear{HaqAlQahtani2005}, see their
Enclosure 2] estimated its age as 211~Ma, and showed it in the Norian
Minjur\unskip\break Formation. 


\citet{DaviesSimmons2018}, revising \citet{Sharlandetal2001}, selected a
new reference location for the MFS Tr80, in Musandam UAE. They
picked the MFS within the Milaha Formation in the first limestone beds
with megalodonts and crinoids, above the marker foraminifer
\textit{Triasina hantkeni} of late \mbox{Middle} Norian to Rhaetian age
[Leopold Krystyn, \citealp{Urbanetal2023}], and below the latest Norian beds
of the Asfal Member (lower part of the Ghalilah Formation) dated by the
ammonoid \textit{Neotibetites} and by the \mbox{conodont}
\textit{Epigondolella bidentata} [\citealp{Maureretal2008,Maureretal2015},
location on Figure~\ref{fig1}].


In accord with the present study, the sequence boundary (Tr80 SB) was
picked in the Early Norian hiatus. 


Additional graphical evidence presented by \citet{Urbanetal2023} reveals
that the boundary of the Milaha Formation and the overlying Asfal
Member of the Ghalilah Formation is an erosional discontinuity marked
by a reworked limestone conglomerate. This erosional discontinuity is
an obvious candidate for an additional sequence boundary, which might
be designated as Tr90 SB. 




\citet{Issautieretal2019} have demonstrated that there are three maximum
flooding intervals (MFI) in the Minjur Sandstone through a 
southwest--northeast transect from outcrop to the Gulf (location on\unskip\break
Figure~\ref{fig1}):
\begin{itemize}
\item \textbf{Early to Middle Norian}: in subsurface, beds containing
the marine dinocyst \textit{Rhaetogonyaulax wigginsii}. In Well 143-3,
the closest to the outcrop (location on Figure~\ref{fig1}), a thick
sandstone interval was deposited between 1050~ft and 1150~ft
(320--350~m), capped by a 50~ft (15~m) thick mudstone interval in which
\textit{R. wigginsii} was found at 1042~ft (318~m) (FDO and LDO). The
palynology study revealed that this shallow marine bio-marker is the
most widespread and could date the peak transgression within the
Triassic portion of the Minjur Formation. The FDO of \textit{R.
wigginsii}, within the palynosubzone T1B, suggests a position close to
the middle--early Norian boundary, following the work of
\citet{NicollFoster1994,NicollFoster1998} who correlated conodont zones
with the ranges of selected dinoflagellate cysts, including \textit{R.
wigginsii}. In outcrop these beds are correlated with Minjur Sequence 4
\citep{Issautieretal2012a,Issautieretal2019} which is characterized, by
a basal braided sand sheet overlain by cross-bedded sandstones
representing tidal channels, bioturbated sandstones, and dolomitic
siltstones representing associated\break mudflats.

\item \textbf{Latest Norian--Early Rhaetian}: in subsurface locations,
beds containing the dinocyst \textit{Rhaetogonyaulax rhaetica}. In the
SW--NE traverse studied by \citet{Issautieretal2019},
\textit{R.~rhaetica} occurrence is restricted to coastal well 628-5. In outcrop,
Issautier et~al.\ formulated three hypotheses: either the \textit{R.
rhaetica} transgression never reached the outcrop or was eroded by the
intra-Minjur unconformity, or the \textit{R. rhaetica} transgression
might be partly equivalent to the transgressive systems tract of upper
Sequence 5, represented by tidal flat and channel facies. 
\citet{Issautieretal2019} also correlated these beds with the Malihah
and the lower Ghalilah formations (Asfal Member) of comparable\break
age in the UAE section \citep{Maureretal2008,Maureretal2015}.

\item \textbf{Latest Rhaetian to Early Pliensbachian}: in subsurface,
beds containing the dinocysts \textit{Dapcodinium priscus,} for which
no MFS \textit{sensu} \citet{Sharlandetal2001} has been identified. In
outcrop, they are likely coeval with the transgressive intervals of the
Minjur\unskip\break Sequences 6, 7, and 8 including marginal marine or tidal
deposits. The upper one is underlined by marine carbonate in the upper
part of the formation and would correspond to the uppermost tidal
channel of Sequence 8. It seems probable that the as yet unidentified
MFS is located in the overlying Early Jurassic (Hettangian--Sinemurian?)
section. A comparable Rhaetian to Early Jurassic transgression can be
identified in Kuwait \citep{Kadaretal2015}. 
\end{itemize}

\citet{Issautieretal2012a,Issautieretal2019} explain the different
extents of the \textit{R. wigginsii} and \textit{R. rhaetica}
transgressions by modified paleogeographic settings. A flatter
landscape with tidal flats during Early--Mid Norian enabled
retrogradation of \textit{R. wigginsii} marine facies to more proximal
settings. A more contrasted landscape during Late Norian and Rhaetian,
with an upstream part supplying abundant clastics deterred landward
retrogradation of \textit{R. rhaetica} facies. 


Fine-grained fluvial-lagoonal and littoral deposits containing
echinoderms debris, were used for subdividing a lower from an upper
unit in the Minjur Sandstone within the Ar Rayn quadrangle by 
\citet{Vasletetal1983}, and within the Al Mulayh quadrangle by 
\citet{Manivitetal1985a}. Due to lack of biostratigraphic constraints,
it is not clear with which of the two Norian MFS's it is associated.
However, the EarthVision\tsup{\text{\textregistered}} 3D model (by B.
Issautier and Y. M. Le Nindre, 2011, unpublished) shows a strict
\mbox{correspondence} between Sequence 4 and the 90--130~m marker of the
Khashm al Khalta section of \citet{Vasletetal1983}, which is taken as
the base of the ``Upper Unit' (Figure~\ref{fig3}a). The ophiurid
vertebrae were observed from the uppermost dolomitic siltstone beds
(sample VD80-122, Figure~\ref{fig4}). 

\begin{figure*}
{\vspace*{-2pt}}
\includegraphics{fig03}
{\vspace*{-2pt}}
\caption{\label{fig3}Learning from the Minjur 3D model at Khashm Al Khalta (Khasm
al M\={a}njur) type locality. (a)~Correspondence between the model and
the section measured by Le Nindre and others in Oct. 1980---see Part
I, \citet{LeNindreetal2023}---with indication of the MFS [Tr80]
horizon, and Jilh Dolomite Tr60. Tr70 is eroded from the North at this
latitude---view from South; (b) Other view---from 
west-southwest---emphasizing the SB4 unconformity (early--mid Norian)
and the pre-Minjur fluvial erosion (Carnian--Norian boundary). Minjur
sequences nomenclature of \citet{Issautieretal2012a}.}
\end{figure*}

\begin{figure*}
{\vspace*{4pt}}
\includegraphics{fig04}
{\vspace*{5pt}}
\caption{\label{fig4}Two remarkable fossils of the Minjur Sandstone: silicified
tree trunk (a), and skeletal piece of Ophiuridea (b).
(a)~Tree trunk (length $\leq$ 5~m, diameter $\leq$ 50~cm) of a Mid
Norian petrified forest near Al Barud (c. 24\textdegree 50$'$~N,
44\textdegree 11$'$~E) Sample JMA83-238, Buraydah quadrangle. Photo J.
Manivit. (b)~Siltstone with angular and splinter quartz,
cemented by dolomicrosparite, detail: typical section of ophiuroid
vertebra reflecting temporary marine incursion into a dominantly
fluvio-deltaic setting (MFS Tr80?). sample VD80-122, B28450, polarized
light, Khashm al Khalta section (c. 23\textdegree 35$'$~N,
46\textdegree 10$'$~N), Ar Rayn quadrangle. Photo Y. M. Le Nindre.}
{\vspace*{6pt}}
\end{figure*}

The base of Sequence 4 truncates Sequence 3 and partially Sequence 2 of
the Minjur Sandstone as a north-dipping surface observed in the field
and modelled (EathVision\tsup{\text{\textregistered}} 3D,
Figure~\ref{fig3}b) by B. Issautier and Y. M. Le Nindre in 2011 [annex
work to \citealp{Issautier2011}].\looseness=-1

\citet{Issautieretal2019} thus assigned the MFS Tr80 to the early
Middle Norian \textit{R. wigginsii} beds, widespread on both sides of
the Qatar Arch as shown by their figure~16 after
\citet{Stewartetal2016}. It matches the Alaunian 1 ages obtained in
Part I of our study, on top of the Jilh Formation and at the base of
the Minjur Sandstone northwards of 25\textdegree 30$'$~N, from\unskip\break ammonoids
and from the conodonts \textit{Ancyrogondolella praeslovakensis}, and
\textit{Epigondolella abneptis} in several sections.


Within this given context, for matter of simplification, and following
\citet{Issautieretal2019}, in the next pages we keep using Tr80 for the
Alaunian 1 regional transgression separated from the Tuvalian Tr70 by a
disconformity of more than 10~Ma. The renaming of Tr80 is out of the
scope of this study. Nevertheless Tr80, Tr90, and either Tr100 or more
likely J05, could be proposed for Alaunian (T1B), Sevatian (T1A), and
latest Rhaetian--Early Pliensbachian (T0-J) transgressions,
respectively. J10 is still in the overlying Marrat Formation. 
\looseness=-1


The Emirates-Musandam section 
\citep{Maureretal2008,Maureretal2015,Urbanetal2023} contains two
transgressive events separated by an erosional discontinuity, the lower
one at the base of the Milaha Formation, the upper one at the base of
the Asfal member of the Ghalilah Formation. The only marker fossil
recorded in the Milaha Formation is the foraminifer \textit{Triasina
hantkeni} which was recovered 21~m above its base and 50~m below the
contact with the overlying Asfal Member 
\citep{Maureretal2008,Maureretal2015,Urbanetal2023}. 
\citet{DaviesSimmons2018} followed other workers in interpreting that
the range of \textit{T. hantkeni} was Late Norian (Sevatian) to
Rhaetian, which accounts for their assignment of the MFS in the Milaha
Formation to the Late Norian. However Urban et~al.\ argue that a Middle
Norian age for \textit{T. hantkeni} cannot be ruled out. This remains
the opinion of one of the authors (LK) We note that \textit{T.
hantkeni} is commonly reported in lagoonal sediments also containing
megalodonts, as is the case of the Milaha\unskip\break Formation, and therefore
wonder if it may have been, at least partially, facies controlled.
Consequently, the lower transgressive event could be (partly)
contemporaneous of the Alaunian transgression in central Arabia, and
the erosional surface capped by a conglomerate that separates the
Milaha and Ghalilah Formations likely represents the same event that
marks the base of Sequence 5 (scour surface SB5) of
\citet{Issautieretal2019}. It would set up the interesting possibility
that the upper transgression in the Asfal Member is (partly) equivalent
to the \textit{R. rhaetica} flooding as suggested by 
\citet{Issautieretal2019}. This would be consistent with the
nomenclature suggested above, namely that the Alaunian transgression
was associated with MFS Tr80, and that the younger Late Norian--Rhaetian
event could represent a newly identified MFS Tr90.


Note that \citet{Lunnetal2019} and \citet{Lunn2020} use ``Tr80''
(previously ``Tr80 v1'') in place of MFS Tr60 within the Jilh
Dolomite unit (see Section~\ref{sec4}: ``Particular events and their
regional correlations''). Lunn assigned a ``Tr 100'' (previously
``Tr80 v3'') to the \textit{R. rhaetica} MFS in Wells 143-3 and
628-5, T1A palynosubzone, referring to \citet{Issautieretal2019}.
Readers should note that Lunn misidentified the Jilh Dolomite
equivalent in well 143-3.


In our study MFS Tr80 is interpreted as early Middle Norian and
the base of the Alaunian is at 217.49~Ma \citep{OggChen2020}. It could
therefore correlate to MFS Nor1 in Time Scale Creator at c. 217~Ma, the
best guess for the age of Tr80 so far (Table~\ref{tab1}).
However, in the \citet{Haq2018} chart, as well as in the Ogg and Chen
chart, this age corresponds to a sea level lowstand; subsequently, this
transgression could eventually match the top of the TNo3 sequence in
the Late Lacian, revealing that broad uncertainties exist on the Norian
sea-level and coastal onlap curves.


In conclusion, at the regional scale (Iran, Iraq, Kuwait, UAE, Oman,
Saudi Arabia), we have not yet in hand all the elements for
establishing a hierarchy of the major flooding events of the Late
Triassic at plate scale. Disagreements between the authors in a broader
spectrum of papers on ages and correlations within this period persist
due to an \mbox{obvious} lack in biostratigraphic data and in numerical ages
for making reliable correlations regardless of the lithologies as we
present now for Saudi Arabia. In particular outcrop paleontological
studies using both ammonoids and conodonts are not developed
sufficiently to confirm correlations in the subsurface using only well
logs or facies associations and need further investigation. 
\looseness=-1

\subsection{Depositional and structural evolution from Ladinian to Norian}


Using the available time markers (datums or assumed), we have split the
geohistory of the Jilh Formation into four stages (Figures~\ref{fig6}a
to \ref{fig9}d). This exercise demonstrates the evolution of the
structural setting, and the vertical and horizontal \mbox{relationships}
between the successive depositional units.


\pagebreak

\onecolumngrid
\begin{sidewaysfigure*}
\vspace*{19pc}
\includegraphics{fig05}
\caption{\label{fig5}Ages and maximum flooding events of the Jilh--Minjur systems
based on marine carbonates stratigraphy.}
\end{sidewaysfigure*}
\twocolumngrid


\begin{figure*}
\includegraphics{fig06}
\caption{\label{fig6}(a)--(d) Stratigraphy of the depositional sequences at four
stages of the Jilh Formation sedimentary history.}
\end{figure*}

\begin{figure*}
\includegraphics{fig07}
\caption{\label{fig7}Stratigraphy of the depositional sequences of the Jilh
Formation from the late Ladinian-basal Carnian low-stand,
horizontalized at the base of Minjur clastics (lithostratigraphic).
Letters and numbers refer to the legend of  Figure~\ref{fig6}(a)--(d).
In addition, (13): Early Norian hiatus disconformity surface; (14):
intermediate Alaunian tidal sequence boundary.}
\end{figure*}




\begin{figure*}
\includegraphics{fig08}
\caption{\label{fig8}Synthetic sequence stratigraphy of the Jilh Formation in
outcrop between latitudes 22\textdegree~N and 27\textdegree~N. Surface
(12): base of the Minjur Sandstone (lithostratigraphic). Early Norian
(pars) present in the Lower Minjur in Central Arabia.}
\end{figure*}


\begin{figure*}
{\vspace*{2pt}}
\includegraphics{fig09}
\caption{\label{fig9}Synthetic conceptual sketch of the Jilh--Minjur systems in
outcrop summarising the main structural features, the geometric
relationships of the depositional sequences, especially the
unconformable Alaunian transgressive wedge.}
{\vspace*{2pt}}
\end{figure*}


In Figure~\ref{fig6}, we have intentionally abandoned the use of the
lithological units J1 to J3 since Part I established diachroneity in
these units. Instead, we introduce letters A to J to denote
``horizons''; i.e., layers with relatively uniform facies and
thicknesses. Several horizons contain individual ``bodies'' that
represent lateral changes in facies or thickness, such as those that
represent the Julian Clastic Event. The numbers 1 to 11 are
``surfaces'', time lines or events (e.g., MFS, SB) and they separate   
horizons that can be interpreted as subaerial sequence boundary (SB),
transgressive (TST) and highstand (HST) systems tracts.


\subsubsection{Top Ladinian datum}


In Figure~\ref{fig6}a the top Ladinian (surface 5) is chosen as the
datum to illustrate that the Anisian and Ladinian facies and structure
are fairly monotonous and relatively uniform in thickness. The top of
the Sudair Shale is generally covered by the Nafud Desert and not
marked by a cuesta, and so it is only known at three points (Khashm
Dolqan by SHD-1 Well, Khabra Halwah, and Al Mudarraj). In the top
Ladinian datum cross-section, the top Sudair is most likely represented
by surface 1, but it could be surface 2 in the south.


The upper part of the Sudair Shale represents the continental early
TST of a sequence that passes to an Anisian late TST (horizon A)
culminating in MFS Tr40 (surface 3), above which horizon B represents
the Anisian HST. Horizons A and B are well dated by pollens and by
\textit{Myophoria goldfussi}, a lamellibranch that commonly
inhabited this kind of brackish environment. Horizon C represents a
younger shallow-marine cycle that includes MFI Tr50 and is dated as
Ladinian by conodonts. A hiatus may occur between Anisian horizon B and
Ladinian horizon C and is a candidate for the\break Tr50 SB.


The upper part of horizon C is marked by a thin Ladinian sequence and
capped by a gypsum deposit at Khashm Dolqan. The contrast between the
gypsum below and clastics above suggests a hiatus (corresponding to
surface 5---candidate for Tr60 SB). The clastics above surface 5 are
not dated; they could be latest Ladinian or more likely early Julian.
They correspond to a change in clastic influx and climate conditions
from arid (gypsum in upper Ladinian) to humid which from \citet{Haq2018},
would correspond to the sea level lowstand 237.5~Ma, TLa3 sequence, at
the Ladinian-Carnian boundary. When compared with the Alps and the
Germanic basin, hiatuses are very likely between the Ladinian evaporite
and the Julian clastics \citep{Hornungetal2007}. We tentatively assign
these clastics to the ``Julian Clastic\break Event''.

\subsubsection{During Julian (Time reference: ?mid Julian condensed interval)}

This datum, which we name ``Julian condensed interval'' (\textit{sensu}
Vail's school), is characterized by\unskip\break Fe-oolite (formerly chlorite?),
glauconite, quartz and intraclasts with reworked Permian fauna (surface
8, Figure~\ref{fig6}b) and estimated by \textit{M. carnica} as
?mid--late Julian. The first observation is the structural change of the
previous deposits, related to a tectonic phase predating and/or
accompanying the deposition of the clastics (horizons D, E and F), but
principally of the two depositional horizons D and E, generally capped
by paleosols. 


Horizon D is assigned to the Julian and characterized by a landscape
of supralittoral shales and creeks with channels of heterometric
fluvial sandstone. Sandstone bodies, in channels in horizon D, become
aggregated in Julian horizon E. Laterally at Jabal al Arid, horizon E
corresponds to the deposition of the first deltaic sandstones 
\citep{LeNindreetal2023}.





Sandstone bodies D and E evolved to Julian sandstone body F by
transgression and reworking of the fluvial sandstone to coastal and
tidal sandstone, which are extensive, relatively sheet-like and uniform
in thickness. Laterally, at Jabal al Arid, a deltaic outlet incises the
coastal sandstone (body G). So, this time interval is characterized
simultaneously by tectonic structuration and clastic influx, filling
lowlands between the structures. At this stage it is difficult to
determine if the basal sandstone and change of regime were driven by a
sea-level low stand, or principally by a change in clastic influx
related to tectonics and climate, or even a combination of these.
Therefore, the base of the Julian Clastic Event (surface 5) can be
considered as a sequence boundary (presumably Tr60 SB) with a possible
hiatus following the Ladinian transgression. A tectonic setting with
sandstone bodies infilling the grabens (and carbonates on the flat
tops) is also common elsewhere during the Triassic. East of the
outcrops, \citet{Faqiraetal2009} interpreted the presence of north--south
trending horsts and grabens that developed in response to regional
extension during the Triassic. In this study, structures such as Qatar
high (south of 21\textdegree 30$'$~N), ``Khashm Fardah (Sitarah)
uplift'' [22\textdegree 38$'$~N, \citealp{LeNindreetal1983}], ``Jilh al
Ishar sag'' (23\textdegree 31$'$~N) and ``Khabrah Halwah uplift''
(23\textdegree 50$'$~N) control the sedimentation. Lineaments in the
basement (N135) or major present valleys as the Wadi Birk
(23\textdegree 10$'$~N) and the Wadi Ar Rimah (26\textdegree 30$'$~N) may
reveal syn-sedimentary fault systems, active during the Triassic, and,
later on, during the Jurassic [Wadi Birk, \citealp{AlMojel2017}]. 

\subsubsection{Carnian--Norian boundary: Early Norian unconformity}

At outcrop, the flat reference taken as base Norian is the
disconformity surface (Tr80 SB) dated by the first Norian occurrence
within the Jilh Formation (Alaunian 1, early Middle Norian) in the
north, or by base Minjur, dated Early to Middle Norian in the centre
where part of the Early Norian is demonstrably absent 
\citep{Issautieretal2019} (Figure~\ref{fig6}c). The main features
raised by this choice of levelling reference are the structure of the
deltaic wedge at Jabal al Arid in the south (upper deltaic wedge, body
H), and a smooth subsident trough in the north (horizon J) through
which the marine transgressions of the latest Julian (surface 9 $=$ MFI
Tr60) and Tuvalian (surface 11 $=$ MFI Tr70) progressed from the NNE.
Clastic inputs persisted laterally (horizon I) during the deposition of
a broad deltaic wedge, clearly visible on DTM and satellite imagery
\citep[see][]{Issautieretal2012a}. This feature enhances the clastic
trough of Jabal al Arid. 


In contrast, the central area of Khabra Halwah remained dominated by
tidal flats and must have been a very low relief setting. The broader
transgression is latest Julian (surface 9) and is detected up to
22\textdegree~N (tidal flat), with more marine conditions (fossils)
northward up to 23\textdegree 30$'$. With time, the next transgressions
are less and less extensive upwards. The orientation of the outcrop,
and consequently of the cross section, shows in fact an oblique view of
the transgressive wedges. They appear in a transversal section with a
south--north progressive regression of the successive pulses that
continued during the Norian (Figure~\ref{fig13}). So, this cycle
reflects a transgressive system up to the latest Julian transgression
(MFS Tr60) followed by a progressive retrogradation of the successive
marine pulses via the Late Carnian MFS Tr70 until the Mid-Norian (MFS
Tr80) later on, although there is clear southwards truncation of the
Tr70 flooding event, indicating regional tectonism (and possibly a
concurrent eustatic sea-level low) associated with the base Minjur
Formation \mbox{unconformity} 
identified in Part I (Figure~\ref{fig6}c). The evaporites
of the northern area mentioned by \citet{Sharief1977,Sharief1986} that
overlie surface 11 represent the post-Tr70 Tuvalian--Lacian regression
\citep{Sharlandetal2001}.


\subsubsection{During Norian (early Mid Norian Transgressive Interval Tr80)}


Descriptions of the Jilh/Minjur boundary from south to north show a
major event generally characterized by lag deposits at outcrop scale.
The deposits are most likely related to a peneplain over the previous
deposits after uplift (in the south) and subsidence (in the north) of
the Jilh Formation. In this interpretation, an erosional unconformity
separates the Jilh Formation from the Minjur Sandstone (Figure~\ref{fig6}d).
Flattening the cross section on top of the Alaunian 1 MFI as
interpreted in this study (early Mid Norian Tr80), emphasises that
south of 25\textdegree 35$'$~N, and especially south of 24\textdegree~N, the
major subsident trough of the Lower Minjur gave way to the main streams
and deltaic wedge of the stacked Jilh and Minjur reservoirs of central
Arabia. As pointed out by \citet{Issautieretal2012a}, this area was
likely a persistently weak tectonic zone. North of 25\textdegree 35$'$~N,
a shallow-marine trough developed during the subsequent regression
within the previously more marine area. 


Away from the main upstream source of clastic supply, the unconformity
separating the Minjur and Jilh formations is difficult to identify in
the more fines-dominated succession to the north, although simple
stratigraphic relationships indicate that a cryptic time gap must be
present in that area.


From the Al Faydah quadrangle to the north of the Buraydah quadrangle
both geological maps \citep{Manivitetal1986,Vasletetal1985b} and
satellite images show an evolution of the Jilh outcrops which spread
out in relation with facies changes.


From the base, during the Ladinian, deposition of sandstone and
dolomite around 26\textdegree 13$'$~N are not observed further south.
Near the top, a cuesta, mapped as the uppermost Jilh lithological
assemblage on the Buraydah geological map \citep{Manivitetal1986} is
developed, seemingly conformably overlain by the cover of fine-grained
sandstone and shale of the Minjur Sandstone, although a significant
time gap is probable. Its facies of grey/yellow argillaceous rocks,
with associated dolomite and evaporites, is similar to the one defined
as the Baluti Shale Formation in Iraq
[\citeauthor{vanBellenetal1959-2005},
\hyperlinkcite{vanBellenetal1959-2005}{1959--2005}] mapped by
\citet{Ziegler2001} within the ``Carnian to Norian paleogeography,
together with the Lower Minjur in a narrow zone of ``marginal-marine to
shallow-marine clastics''\unskip\break (Figure~\ref{fig13}). The presence of this
marginal-littoral to shallow marine facies, with the
\textit{Tropitidae} fauna, below, and the \textit{Tibetitidae} fauna
above, reflects a smooth trough that was penetrated from the north by
successive marine ingressions (26\textdegree 15$'$~N, ``Safra ar
Ruwaydah inlet''). 


The lithological assemblage dated Norian by the conodonts and the
ammonoids is thus part of the Lower Minjur, and confirms more marine
conditions. The present-day morphological character of Wadi Ar Rimah
area is probably related to an ancient deep structural feature that was
active from Ladinian to Norian. From MFS Tr60, although interrupted by
the Early to Middle Norian unconformity, the depositional system was
overall regressive with a culmination during the Rhaetian, associated
with a reactivation of the hinterland erosion and creation of alluvial
fan and of hyperpycnic bodies.

\subsection{Carnian--Norian back-stepping, progradation, and diachronism}


Coming back to the interpretation of a diachronism of the depositional
lithostratigraphic units by J. Manivit and B. Vrielynck [{in}
\citealp{LeNindreetal1987}, DrSc theses, and
\citealp{LeNindreetal1990b}, p.~187, Figure~38, and this study, above] it
is now possible to decipher this conclusion more clearly. By using the
method of the Figure~\ref{fig6}a--d, we have flattened the Carnian--Norian
deposits at the time of the Minjur ``petrified forest''---coarse
grained clastics, trunks and wood debris---which reflect a change in
climate and tectonics and was taken as lithostratigraphic base of the
formation (Figure~\ref{fig7}). This event erodes the previous marginal
marine deposits.


This representation depicts, besides a diachronic lithostratigraphy,
principally the mechanisms it originates from. Following the sea level
lowstand at 237.5~Ma, during the Early Carnian, the sequences are
essentially transgressive and landward backstepping until the latest
Julian Tr60 maximum flooding, reaching up to Lat. 22\textdegree~N
southward. Younger sequences are dominantly regressive and accompanied
by a northward seaward progradation. Thus, MFS Tr60 represents the most
prominent transgression, which accords well with the plate-wide
correlation of the Jilh, Sefidar and Marker Dolomites.


A similar hypothesis was formulated for the Gulailah Formation in Abu
Dhabi by \citet{Huetal2015} who divided the Jilh-equivalent
Gulailah Formation into Lower and Upper Units, with the lower unit
being more layer cake and the upper more regressive. They do not appear
to have considered differential erosion beneath a base Minjur Formation
unconformity.


The picture is complicated by two superimposed unconformities: the
Early Norian hiatus in the marginal marine area (north), and the
pre-Minjur erosion, in the fluvial-deltaic domain (south), and
principally in the axis of the Minjur inlet 
\citep[see][]{Issautieretal2012a,Issautieretal2019}. Consequently, it
is not possible to determine how far the Tuvalian transgression had
reached before truncation by the clastic channels. This configuration
is likely due to an uplift of the hinterland during the Early--Mid
Norian causing its erosion and thus an increased clastic influx.


Southeastward, in the Rub al Khali Basin of central to eastern Saudi
Arabia, \citet{DevilledePeriereetal2022} interpreted that the Late
Carnian to Early Norian tectonic pulse that generated the unconformity
was responsible for the uplift of paleostructures such as the Qatar
Arch and the widespread differential erosion of the Jilh Formation.



\section{Synthesis of sequence stratigraphy}

The stratigraphic evolution of the Jilh and Minjur Formations along
the outcrop belt is summarized in Figure~\ref{fig8}, which compiles the
elementary sequences described along the steps (a) to (d) on the cross
sections. This evolution is summarised below:


\textbf{Anisian transgression (horizon A)}: Starting from the
continental shales and evaporites of the Sudair Shale, the sequence
boundary (surface 1) at the bottom is marked by sand input and coal
seams. Then, the Anisian shows a period of transgression through salt
marshes, with plants and pollens, lagoonal shales and evaporites,
ending with transient tidal flats (MFS Tr40, surface 3).


\textbf{Anisian regression (horizon B)}: A more confined, possibly
lagoonal, setting represented by brackish shale and sandstone and the
lamellibranch \textit{Myophoria goldfussi} completes the HST of the
Anisian\break cycle.


\textbf{Ladinian cycle (horizon C)}: A coarse-grained reworked
horizon with plants and vertebrate (reptilian and fishes) bone debris
marks the sequence boundary (surface 4 $=$ Tr50 SB). It is followed by a
rapid regional shallow-marine flooding with a diversified fauna and
algae, well dated by conodonts along the outcrop belt (MFS Tr50). It is
followed by a regression leading to gypsum deposits in the reference
section. In the Ladinian paleogeography, this event likely corresponds
to generalized evaporite deposits and to the end of the first arid
period. It may be correlated to the sea level low stand from 238 to
237.5~Ma, TLa3 SB of \citet{Haq2018} and \citet{OggChen2020}. 


\textbf{Julian Clastic Event (horizons D to F, and body G)}: A sharp
change occurs in sedimentary conditions with the beginning of a period
of major clastic influx marking the Julian sequence boundary (surface 5
$=$ Tr60 SB). Erosional hiatuses may separate the Julian from the
Ladinian as explained above. In a landscape of a littoral plain,
several fluvial sequences are stacked: horizons D and E, with
coarse-grained sandstone and overturned stratifications, capped by thin
lagoonal deposits. With progression of the transgression, the sand
brought by the river was reworked into coastal/tidal sandstone (horizon
F), interrupted by some distal fluvial/estuarine outlets (body G).


\textbf{Julian Transgression (body H and horizon I)}: Following the
Julian Clastic Event, the transition from clastic to carbonate is
underlined by the ``TSF'' 
[Time Specific Facies, \citealp{Brettetal2012,PaviaMartire2015}],
which marks the ongoing transgression with quartz Fe-oolites,
glauconites, and intra/extraclasts (surface 8), and some fauna. Deltaic
influences persisted in the Jabal al Arid area (body H), but the
overall trend is the generalized expansion of tidal flats and an
increasing marine influence (horizon I). During the late Julian, the
shallow-marine ingression, dated by conodonts and accompanied by marine
fauna and cushion stromatolites, reached its maximum (MFS Tr60, surface
9). It was followed by a brief return to more lagoonal conditions
representing the succeeding HST.


\textbf{Tuvalian transgression (horizon J)}: Several high-frequency
cycles of transgression-regression are recorded in the carbonates of
the northern area. They can be considered as part of a new
shallow-marine transgression accompanied by a rich marine fauna
including ammonoids, and recorded north of 25\textdegree~N (MFS Tr70,
surface 11). The cycle is completed by a return to restricted
conditions during the subsequent HST, though this is variably preserved
because of erosion beneath the Early to Middle Norian unconformity
(Tr80 SB).


\textbf{Norian transgressive--regressive cycles}: A new short-lived
transgressive pulse of limited lateral\unskip\break extent is recorded during the
Norian north of 26\textdegree~N as shown by thin carbonate layers and the
presence of Norian marker conodonts. The sequence boundary corresponds
to a hiatus, owing to the presence of marker conodonts and of
\textit{Tibetitidae} of Alaunian 1 age found in a transgressive
horizon not far from the Carnian/Norian boundary. Transient returns to
evaporite deposits reflect temporary, higher frequency regressions. 


One result of this study is the concept of an early Alaunian wedge,
corresponding to the Sequence 4 of \citet{Issautieretal2019}
tentatively correlated in outcrop from latitudes 22\textdegree~N up to
27\textdegree~N on the basis of similar ages and of a regional
flooding event, assigned herein to MFS Tr80, and which truncates the
underlying Minjur Sequences 2 and 3 (SB4 unconformity)
(Figure~\ref{fig9}). However continuous correlation between north and
south remains uncertain between latitudes 25\textdegree~N and
26\textdegree~N (Al Faydah quadrangle) where the Minjur Sandstone is
covered by aeolian\unskip\break sand. 


This chronology is comparable with the one proposed by 
\citet{KorngreenBenjamini2010} for the northern Arabian Plate. The
Mohilla Formation cited in the paper contains abundant interbedded
volcanics which complicates interpretation but even so five low-order
(LO) cycles were identified and integrated into a
sequence-stratigraphic model with eustatic, tectonic, and differential
subsidence components: LO Cycle 1 is Late Anisian (Pelsonian), Cycle 2
is Late Anisian to Longobardian, Cycle 3 is Early Carnian, Cycle 4 is
Late Carnian, and Cycle 5 is at the Carnian--Norian transition.
However, Cycle 5 is likely missing by erosion in Saudi Arabia and over
most of the Arabian Plate, being replaced by the early Norian hiatus,
but probably preserved in the Israeli boreholes because of their
locations towards the western margin of the Arabian Plate. There is no
equivalent to the Minjur Sandstone in Israel because of Late Triassic
rift-related uplift, thus the pre-Minjur unconformity is almost
certainly merged with the younger Latest Triassic--Early Jurassic
unconformity [End Triassic unconformity of \citealp{Lunnetal2019}].\break
\mbox{Jurassic}
volcanics or sediments overlie the incomplete~Cycle~5.


As mentioned by \citet{Issautieretal2012a} the Minjur clastics may
originate from a regional uplift of the hinterland related to a thermic
dome as modelled by \citet{LeNindreetal2003}.


{\vspace*{-1pt}}

\section{Particular events and their regional correlations}\label{sec4}


Jilh sedimentation is marked by important clastic influx, especially
during the early Julian alternating with biogenic and chemical deposits
such as carbonates and evaporites, following tectonic or global
changes. It displays marked lateral facies change into shales,
dolomites and anhydrites in the Ghawar area subsurface 
[\citealp{Zhouetal2009}, location on Figures~\ref{fig1}
and~\ref{fig12}]. Carnian clastics events are well documented in the
literature (``Carnian pluvial event''). In contrast, the precise
timings of evaporite in the sequence are less well constrained even
though Carnian evaporites are common across the Arabian Plate
(``Carnian Salinity Crisis''). These alternations are controlled by a
combination of tectonic phases, such as the Late Ladinian--Early
Carnian rifting, and climate changes which have regional consequences
recorded in the sedimentation. Hence, carbonate and evaporite marker
horizons can be followed at a plate scale. Thus, the MFS identified in
this study (Tr40, Tr50, Tr60, Tr70 and Tr80) should all be readily
correlated, except, where eroded beneath regional unconformities.
Therefore, in this section we set the early Norian unconformity
demonstrated herein in the context of more regional Carnian--Norian
hiatuses.

{\vspace*{-1pt}}

\subsection{Age and cause of the Julian Clastic Event}


Based on structural considerations and on ages of the events described
at the Ladinian/Julian boundary in section ``Depositional and
structural evolution\ldots'', above, it seems likely that the Julian
Clastic Event and its lateral variations, and probable hiatus between
Ladinian and Carnian are related to a second phase of Neo-Tethyan
extensional tectonics---first phase at the Permian-Triassic 
boundary---which occurred during this period in the eastern part of
the Arabian Platform [\citealp{LeMetouretal1995}, \textit{in} 
\citealp{Ziegler2001}]. \citet{LeNindreetal2003}, also invoked a
\mbox{thermal} doming causing erosion of the hinterland during the Late
Triassic time. \citet{Ziegler2001} also mentions that: ``early in the
Carnian a very pronounced relative drop in sea level was recorded
throughout the circum-Mediterranean region''.


Following this rifting phase, a contrast between Late Ladinian marine
carbonate below and locally coarse clastic deposits above is observed
in the\unskip\break studied area as well as for instance, in the Tarasci section
(Taurus autochthon) in Turkey \citep{AsseretoMonod1974}. At the scale
of the Arabian platform, these Early Julian Clastics likely represent
the time gap separating the Ghail Formation, dated Olenekian to
Ladinian (-Carnian?), from the overlying Milaha Formation, dated Mid
to-Late Norian in the Emirates Musandam \citep{Maureretal2008,Urbanetal2023}.
\looseness=1


Later on, field and well descriptions of the Jilh Formation and of the
Minjur Sandstone show interfingering of clastics, dolomite, and
evaporite. So, both the Julian Clastic Event and Jilh evaporites (see
next section ``Jilh evaporites'') could be partly related to these
tectonic events. This interpretation is favoured over one due solely to
climate change, as invoked with the Carnian Pluvial Event (CPE)
recorded in the Alps and the German Basin for the late Julian or the
Julian/Tuvalian boundary 
\citep{Claudel1999,Gaetani2010,Sommaetal2008}. In the Jilh, this
interpretation might explain the latest deltaic event (body H of J3),
but it does not match the main clastic event which predates
\textit{Mazzaella carnica}, and it is contradictory to carbonate
dominance during the latest\unskip\break Julian. 


However, according to \citet{ArcheLopezGomez2014} the ``Carnian Pluvial
Event'' occurred over large tracts of Central Pangea. It was a
short-lived event (${>}$1~Ma), coeval with a marked sea-level fall and
active rifting. These authors have identified the CPE in the Iberian
Peninsula as a continental clastic wedge forming the Manuel Formation
and coeval sediments, in between marine evaporite formations during a
marked sea-level drop event; its age is considered to be Julian by
palynological and paleogeographic considerations. They propose, for
this period, a new correlation of the sediments of the Iberian
Peninsula with coeval sediments of Western Europe, NW Africa and
Eastern North America, demonstrating that the geographical extent of
the siliciclastic sediments related to the CPE was much larger than
accepted before.


\subsection{Jilh Dolomite}

The Jilh Dolomite is a term used to denote a distinctive interval of
clean dolomites widely identified from Kuwait to Abu Dhabi, the eastern
Rub al Khali Basin and Oman 
\citep{DevilledePeriereetal2022,Obermaieretal2012}. 
\citet{DaviesSimmons2018} interpreted it as of Early Carnian age
containing their Tr60 MFS, whereas \citet{Lunnetal2019} correlated it
with their ``Marker Dolomite'' which they consider a plate-wide marker,
also identified in Iran, Iraq, Syria and Jordan. \citet{Lunnetal2019}
assigned a Latest Carnian age to the Jilh Dolomite and picked their
Tr80 MFS initially at its base, although \citet{Lunn2020} shifted the
pick higher to within the unit. Given these published disagreements, we
propose to use our new data to provide a more definitive
interpretation. 


\subsubsection{Definition}

The subsurface ``Jilh Dolomite'' is characterized as a tight interval
of approximately 30~m thick and c. 25 to 75~m beneath the Minjur
Sandstone. It has very distinctive wireline responses, sharp,
cylindrical, with a low gamma ray, a low porosity, a high sonic
velocity, and the grain density of dolomite, facilitating recognition
as the regional ``Dolomite Marker'' in wells (see Section~\ref{sec2},
Triassic Stratigraphy of the Arabian Plate). 


\subsubsection{Ar Rub al Khali Basin (Saudi Arabia)}


In the central Rub al Khali Basin, \citeauthor{Stewartetal2016} 
[\citeyear{Stewartetal2016}, location on Figure~\ref{fig1}] show this
tight dolomite interval with an average thickness of c. 30~m. at the
boundary with the Minjur sandstones near the Qatar Arch, (although its
identification in their well B appears to be in a limestone and may be
an older unit), and up to c. 300 feet (91~m) deeper eastward in the
basin at the well Lekhwair-70 in Oman (location on Figures~\ref{fig1}
and~\ref{fig12}). It is eroded on top of the Qatar Arch. The
Minjur Sandstone is similarly eroded. Both are unconformably overlain
by the Jurassic. Note that the well denoted ``A'' in central Arabia is
Well 143-3 of \citet{Issautieretal2019}.


In the north Rub al Khali Basin, \citet{DevilledePeriereetal2022} show
the same horizon, which includes a marine median limestone band, with
an average thickness of c. 32~m, and lying c. 115~m beneath the Minjur
Sandstone. While they do not present sampling information, Deville de
Periere et~al.\ display age interpretations based on palynology that
indicate that the Jilh Dolomite is of Carnian, and almost certainly
Early Carnian age given the proximity of the underlying Ladinian beds.
Along the eastern flank of the Qatar Arch, it is considerably reduced
and probably missing by truncation over the Arch itself. The preserved
Jilh Formation is immediately overlain by a residual Minjur Sandstone
or directly by Jurassic limestone. The most complete section is in
their Well~L. Comparison with Well G of Stewart et~al.\ identifies this
as the same well and therefore located in the Shaybah Field (location
on Figure~\ref{fig1}). 


\subsubsection{Abu Dhabi}


In Abu Dhabi, \citet{Taheretal2012} in connection with tight gas
exploration, present a cross section of the Gulailah (Jilh)--Minjur
succession (Location on Figure~\ref{fig1}). The Gulailah Formation was
deposited in similar environments than the Jilh Formation, and, with
marked thickening towards the east-northeast that Taher et~al.\ 
interpreted as due to progradation into an intrashelf basin rather than
differential truncation beneath the base Minjur unconformity. The
``Jilh Dolomite'' is easily recognized through its typical wireline
response with an average thickness of c. 30~m, with a low permeability.
The MFS Tr40 50, and 60 can tentatively be identified through the
wireline response and by comparison with the Ghawar section of 
\citet{Zhouetal2009}, respectively at c. 90, 220, and 370~m above the
base of the formation. The upper part of the formation is truncated
towards the north by the pre-Minjur and pre-Marrat unconformities in
relation with the Qatar Arch. In the south, in the wells N and S, the
lithological unit above the Tr60 ``Jilh Dolomite'' and beneath the
Minjur (c.~195~m) could be assigned to the Tuvalian (MFS Tr70 at 
c.~515~m, in part or in totality, by analogy with the northern outcrops of the
Jilh Formation. This would be consistent with the interpretations of 
\citet{DaviesSimmons2018} concerning the equivalent stratigraphy in
neighbouring parts of Oman \citep{Obermaieretal2012}. Thicknesses are
estimated from the isopach map, figure~5 of \citet{Taheretal2012}. 


\subsubsection{Central Arabian Basin}

According to \citet{Khanetal2015}, in the Central Arabian Basin, in
eastern Saudi Arabia, the ``Jilh Dolomite'' member forms a 90--100~ft.
(27--30~m) thick blocky and laterally persistent unit in the upper part
of the Jilh succession, with generally low log porosities of 5--10\%,
although some higher measured core porosities (up to c. 30\%) are
recorded. From a Sequence Stratigraphy point of view, using
palynological data, they assigned it to the Early Carnian MFS Tr60,
which is in accord with the conclusions of the current study. 


In the Ghawar good examples are provided by the wells A2 and B3 in the
Ghawar area, east-central Saudi Arabia \citep{Zhouetal2009}. Here, the
``Jilh Dolomite'' is easily recognized through a complete set of
wirelines. It matches an interval of c. 45~m thick between the horizons
JLDM (top Jilh Dolomite) and BJDM (base Jilh Dolomite) and c. 45~m
below the Minjur Sandstone.


In the central Arabian Basin, \citeauthor{Lunn2020} [\citeyear{Lunn2020},
his figures~4 and 6], incorrectly interpreted the correlations of the
``Jilh Dolomite'' in the Minjur cross-section from
\citeauthor{Issautieretal2019} [\citeyear{Issautieretal2019}, their
figure~14]. 
\begin{itemize}
\item First of all, the ``Jilh Dolomite'' (12~m) was picked in a
layered shale--dolomite interval, c. 25~m below the base Minjur whereas
the ``dolomite marker'' appears 50~m deeper, with a sharp contrast in
wireline response between shale, above, and dolomite, below.

\item This clayey--dolomitic interval was correlated with a dolomitic
bed at the base of the Khashm al Khalta section in outcrop. The latter,
in fact on top of the Jilh al Ishar--Jabal al Arid Jilh section
[23\textdegree 36$'$~N, \citealp{Vasletetal1983}] is the ``Jilh
Dolomite'' dated by \citet{LeNindreetal1987,LeNindreetal1990b} as
Carnian age by the conodont \textit{Quadralella polygnathiformis} [see
Part I,  \citealp{LeNindreetal2023} and its Appendix A4], the most
landward faunal indicator of the MFS Tr60 in outcrop (see
Figure~\ref{fig5}).
\end{itemize}


\subsubsection{Correlations}

The ``Jilh Dolomite'' or ``Dolomite Marker'' is identifiable at
the scale of the platform, as shown by the ``Triassic regional
stratigraphic correlation panel Jordan--Syria--Iraq--Lurestan--Kuwait--Saudi
Arabia. (Datum: base Marker Dolomite)'' of \citet{Lunn2020}, his figure~6.
This correlation plate demonstrates that, starting from the outcrop
sequence through the Ghawar \citep[][see above]{Zhouetal2009}, two major
transgressive dolomitic horizons are always present: the (late)
Ladinian containing the MFS Tr50, and the late Early Carnian Tr60.
Through all these sections, it is interesting to observe that:
\begin{itemize}
\item The uppermost dolomite of the section Jilh al Ishar--Jabal al
Arid Jilh section (Section A, Part I, 23\textdegree 36$'$~N), is the
``Jilh Dolomite'' in outcrop and is dated of Carnian age by the
conodont \textit{Q. polygnathiformis} (see Part I), and the most
landward faunal indicator of the\break MFS Tr60.

\item Sequence 1 of \citet{Issautieretal2012a,Issautieretal2019}
``Transition Jilh--Minjur'', above the ``Jilh Dolomite'' of the Jilh al
Ishar--Jabal al Arid section and below the first fluvial beds of the
Minjur Sandstone in Khashm al Khalta, may correspond, by its evaporite
and clastic content, and by the correlation done, to the intermediate
sequence observed in wells [e.g., Sequence 4 of
\citealp{DevilledePeriereetal2022}]. So, it would correspond to a
residual, evaporitic, undated Tuvalian, on the basis of a Late Carnian
age of this intermediate lithological unit in other wells (T2A
palynosubzone). 
\end{itemize}


\subsection{Jilh Evaporites}

In the Middle East, thick Triassic evaporites occur in several
formations that are coeval with the Jilh Formation. They are sometimes
grouped together as the ``Carnian Salt Crisis'' 
\citep{AlHusseini2008,HaqAlQahtani2005,Lunnetal2019,Sharlandetal2001,Sharlandetal2004}.
These evaporites are referred to as the ``Jilh Salt'' in subsurface
Saudi Arabia, ``Middle Salt'' in Kuwait, Kurra Chine Salt or Lower
Kurra Chine Evaporite in Syria, the Zerqa (Zarqa) Gypsum or Halite in
Jordan, and Evaporite members of the Dashtak Formation in Iran. This
``salinity crisis'' \citep{Hirsch1992} expressed itself in the
epicontinental regions as a typical lowstand evaporite sequence
dominated by halite and sulphate deposition, continental sands, marls
and shales. Evidence from the Palymyride Trough in Syria is of very
shallow water deposition throughout the thick Triassic section 
\citep{Lucicetal2010}, indicating that sedimentation generally
maintained pace with the creation of accommodation space even in areas
prone to greater subsidence. 


\subsubsection{Surface Saudi Arabia}

Our study indicates that the Jilh Formation in outcrop contains
disseminated evaporitic beds rather than a major evaporitic interval
clearly differentiated in the stratigraphy as \citet{HaqAlQahtani2005}
had suggested in their chart. This is likely due to the proximal
outcrop setting which corresponds to a marginal location where
siltstone--claystone deposition dominated over evaporites
(Figure~3, Part I) which are more concentrated in central or
eastern depressions \citep{Glintzboeckel1981,Ziegler2001}. However
horizons with evaporitic or pre-evaporitic facies are observed: (1) in
the Anisian of Unit J1; (2), in the Ladinian--?early Julian Unit J1,
essentially in the reference section (24\textdegree 15$'$~N); (3) in the
latest-Julian--?Tuvalian Unit J3 between 24\textdegree 30\textdegree~N and
23\textdegree 30$'$~N (Khabra Halwah, Khashm al Khalta), and (4) in the
Norian Unit J3, north of 26\textdegree~N. Elsewhere, evaporites occur as
thin intercalations within the dolomitic tidal flats and algal mats of
sabkha deposits of the formation. In this discussion we review the age
interpretations of various evaporitic units in other regions and their
relationship to the Jilh outcrop in Central Arabia.
\looseness=-1

\subsubsection{Subsurface Saudi Arabia}

In subsurface Saudi Arabia, \citeauthor{HaqAlQahtani2005} 
[\citeyear{HaqAlQahtani2005}, see their enclosure 2] show the Jilh
evaporite in mid-Carnian, immediately pre-dating Tr70, and above the
``Lower Jilh'', although we would caution that their model was based on
the flawed \citet{Sharlandetal2001} interpretation. Comparison with the
original definitions in the reference section of the ``Lower Jilh''
and ``Upper Jilh'' indicates that the former corresponds to
Anisian--Ladinian Unit J1 (Figure~2, Part I). The position of
the Jilh evaporite in lowermost Unit J2 strongly implies an early
Julian rather than a mid-Carnian age. An early Julian age is in
agreement with the age of the ``Carnian Salt Crisis'' of
\citet{Ziegler2001}, who related the evaporites to the sea-level
lowstand of the early Carnian ``Saharan Salinity Crisis''. It is also
consistent with the Julian age for the ``Carnian Salt Crisis'' in the
Middle East, based on ostracods and palynomorphs determined by
\citet{Gerryetal1990}. 



The regional vertical distribution of the Jilh Evaporite into four
stages is shown by \citeauthor{Issautieretal2019} 
[\citeyear{Issautieretal2019}, their figure~16, p.~166]:
\begin{itemize}
\item The Anisian evaporite, predates the dolomite and tidal flats of
the transgression Tr40.
\item The Mid Ladinian evaporite, corresponds to the coastal plain and
sabkha deposits (gypsum silts and clays) underlying Ladinian MFS Tr50
in outcrop (Figure~3, Part I).
\item  The Late Ladinian--early Julian evaporite corresponds to the
gypsum above MFS Tr50 in the reference section at Khashm Dolqan and to
the relative lowstand near the base of the Julian clastics. These two
episodes are coeval with the coastal plain/sabkha deposits shown in
Figure~3, Part I. They occur above and below the Ladinian tidal flats
and, together with the Julian clastics, match the Early Carnian Salt
Crisis of \citeauthor{Ziegler2001} [\citeyear{Ziegler2001}, his figure~5].
\item The Tuvalian evaporite is locally observed above the dolomite
Tr60, as for instance in Minjur Sequence 1 of \citet{Issautieretal2012a} which
\citet{Issautieretal2019} correlated with the T2A palynosubzone in the
nearest Well 143-3 [Well A of \citet{Stewartetal2016}, location 
on Figure~\ref{fig1}].
\end{itemize}

In summary, compiling well logs 
\citep[e.g.,][]{DevilledePeriereetal2022,Lunn2020,Zhouetal2009}
shows that the Jilh evaporites in subsurface Saudi Arabia are commonly
interstratified as anhydrite stringers within dolomitic beds between
the two major flooding intervals Tr50, Ladinian, and Tr60, Julian
(``Jilh Dolomite''), thus time equivalent with the ``Julian
Clastics'', as well as preceding the Ladinian flooding Tr50 and in the
Anisian. Anhydrite stringers may also be observed in the Norian portion
in equivalence with the Alaunian 1 evaporite described in the field,
north of the Wadi ar Rimah (Lat. 26\textdegree~N, North Wadi ar Rimah and
Ibn al Fuhayd sections). 


\subsubsection{Northern Arabian Plate}


In the northern Arabian Plate, \citet{SadooniAlsharhan2004} described
an Anisian--Ladinian ``Keuper type'' evaporite and an early Carnian
``Raibl type'' (``Pan-Mediterranean salt crisis''). These evaporites
correlate to the Anisian and Ladinian--early Julian evaporites in the
Saudi Arabian outcrops. In the Minagish and Burgan fields in Kuwait
(location on Figures~\ref{fig1} and~\ref{fig12}),
\citet{Lunn2020} mentioned it as ``Jilh Salt'' in between two major
dolomitic intervals which, similarly, corresponds to the same Ladinian
and Julian MFI's, referring to current study,
\citet{DaviesSimmons2018}, and to larger scale correlations.


Equivalences of the Norian evaporite mentioned in the Jilh Formation
and at the base of the \mbox{Minjur} Sandstone north of the Wadi ar Rimah
(26\textdegree 30$'$~N, see Part I, Appendix A1) are not well documented
at the regional scale. A likely coeval evaporite restricted to the
northern Arabian Basin is mapped by \citeauthor{Ziegler2001}
[\citeyear{Ziegler2001}, his figure~6]. It is uncertain whether the
?Lacian--Alaunian evaporites represented by \citet{Sharlandetal2004}
associated with hiatuses in Jordan (Abu Ruweis Formation) and Syria
(Mulussa Formation or in Iraq (Upper Kurra Chine Formation) may be time
equivalent.

\subsubsection{Iran}

In the Iranian Zagros, the Dashtak Formation represents the Middle to
Late Triassic \citep{JamesWynd1965}. Biostratigraphic control is
limited. \citet{SzaboKheradpir1978} recognised four 
carbonate--evaporite cycles in the Dashtak Formation that could be
correlated the length of the Zagros (e.g., Dashtak-1 and Kuh-e-Siah-1
wells, location on Figures~\ref{fig1} and~\ref{fig12}). This
four-fold stratigraphic layering continues to be identified in multiple
recent publications including \citet{HajianBarzietal2015},
\citet{DaviesSimmons2018},  \citet{EsrafiliDizajiDalvand2018} and
\citet{Horbury2018}, demonstrating the utility of these subdivisions. 

The sequence stratigraphy of the Dashtak Formation by 
\citeauthor{Sharlandetal2001} [\citeyear{Sharlandetal2001}, p.~190--191
and their figure~3.22] was revised by \citet{DaviesSimmons2018} and may
be correlated with the Jilh Formation at outcrop: the Dashtak Evaporite
A corresponds to the Sudair Shale, Evaporite B matches the top of the
Anisian sequence. Evaporite C occurs between MFS Tr50 and Tr60 (the
Sefidar Dolomite Member, (alias ``Jilh Dolomite'') and would match
the late Ladinian--Early Carnian Julian Clastics and evaporites in
Saudi Arabia \citep[][their figure~3]{DaviesSimmons2020}.
Anhydrite stringers interstratified in the limestone above Tr70 and
below J10SB (Neyriz Formation) are differentially preserved beneath the
unconformity truncating the Dashtak Formation, where the two
unconformities identified in this study are superimposed. Hence these
stringers are much more likely equivalent to the highstand overlying
MFS Tr70 than the Alaunian evaporite present north of the
25\textdegree 30$'$~N in outcrop in Saudi Arabia (see 
Figure~3,\break Part I).


\subsection{Baluti formation and Carnian--Norian unconformity}


For a better understanding of this Early to Middle Norian time gap, it
is worth briefly considering stratigraphic data from the northern
Arabian Plate. The Baluti Formation, is mentioned by Ziegler in its
paleogeographic map of the Late Triassic (Tr60-J10) as a narrow
southward incursion of ``shallow marine to marginal marine clastics''.
Although lying in the Ladinian-Liassic interval, the Baluti Formation
was originally accepted as of Rhaetian age, by regional correlation in
the Stratigraphic Lexicon of Iraq 
[\citeauthor{vanBellenetal1959-2005},
\hyperlinkcite{vanBellenetal1959-2005}{1959--2005}] and thus not
synchronous with the early Mid Norian transgression. However,
uncertainty continues with respect to the age of the Baluti shales and
recent publications present contradictory interpretations of its
regional correlations at the scale of the Arabian Plate. For example,
\citet{Sharlandetal2004} positioned the Baluti clastics above an early
Norian unconformity, between the Upper Kurrachine Formation (dolomite)
and the Butmah Formation, in the late Lacian. In their model, the
Baluti Formation predates the Tr80 MFS positioned in the Early
Alaunian. This interpretation is not far from the schema proposed for
the Jilh--Minjur in our present study but in detail cannot represent the
true Baluti Formation as defined by \citet{Lunnetal2019}.


\citet{Lunnetal2019} commented on the confusion concerning the Baluti
shales, noting that the term was not used consistently in outcrop and
subsurface sections in northern Iraq. In detail they stated that
\citet{Sharlandetal2001} misapplied the term to three separate shales
(``Shales 1--3''), According to \citet{Lunn2020}, only ``Shale 2''
corresponds to the true Baluti shales. Palynological data for this
``Shale 2'' in Well Atrush-1---location on 
Figure~\ref{fig12}---[figure~6 of  \citealp{Lunnetal2019}], provides a
general Carnian age, and show a palynoflora discontinuity in the Lower
Sarki Formation between 2155~m (LDO of \textit{Classopollis}, Late
Norian) and 2170~m (FDO of \textit{Partitissporites}, Carnian).
\citet{Lunnetal2019} mentioned a Tuvalian (late Carnian) age based on
proprietary data from Jebel Gara in northernmost Iraq, although another
palynological study by  \citet{Hanna2007}, stated a Julian (Early
Carnian) age for the basal Baluti at the same locality with a possible
Norian age for the uppermost beds of the formation. \citet{Azo2020}
also interprets the Baluti shales as being partially of Julian age.
Thus, the biostratigraphic data available to date remains equivocal and
does not refute our interpretation that the ``Marker Dolomite'' that
underlies the Baluti Formation is older than previously interpreted and
of Julian (Early Carnian) age, and therefore equivalent to the Jilh
Dolomite of Saudi Arabia and neighbouring countries, as proposed by
\citet{Lunnetal2019}. A further consequence of this interpretation is
that the thick carbonate--evaporite cycles that form Kurra Chine B and
C, as observed in Jebel Kand-1, are most likely of Ladinian to Julian
age, and therefore represent higher frequency events that are only
easily recognised in areas of increased sedimentation where rapid
subsidence generated significant accommodation space. This has
important implications for the regional extent of the
source--reservoir--seal combination identified in Kurra Chine B in
northern Iraq\unskip\break \citep{Lunn2020}. 




From the figures~1 and 3 of \citet{Lunn2020}, the shale portion
of the Baluti Formation in subsurface (e.g., wells Jebel Kand-1 and
Sheikh Adi-1 near Atrush-1---location on Figure~\ref{fig12}) is
clearly above the Kurra Chine A Dolomite Marker and evaporite sequence,
with a sharp contrast above and below suggesting discontinuities. We
have explained above in section ``Jilh Dolomite'' how this marker
corresponds to the Late Julian MFS Tr60. \citet{DaviesSimmons2020} in a
discussion of  \citet{Lunnetal2019} suggest the Baluti Formation (Shale
2) may comprise two distinct units: a lower main portion of Carnian
(possibly Tuvalian) age---overlying the Kurrachine Formation and
representing the highstand above MFS Tr60---and a minor upper portion,
of Late Norian (Sevatian age)---underlying the Sarki (${=}$ Butmah
\textit{sensu lato}) Formation---separated by a major time hiatus. This
disconformity---although not pointed out in these papers---appears
implicitly above BS.25 as ``CRN or NOR'' (i.e., ``Carnian or Norian'',
BS.34-35) in the palynological chart of \citealp{Lunnetal2019}, their
figure~4 [after  \citealp{Hanna2007}], Jebel Gara section. In this
chart, the shale portion of the Baluti Formation strictly corresponds
to the Baluti shales of the well logs, while the upper limestone
portion corresponds with the Lower Sarki/Butmah of the well logs.
Erosional relief on this unconformity, comparable to that identified in
Saudi Arabia (this study) means that a more complete Tuvalian section,
including beds containing MFS Tr70, is almost certainly differentially
preserved across northern Iraq. Further biostratigraphic analysis of
the Kurra Chine, Baluti and Sarki Formations, particularly focused on
conodonts, in multiple sections is recommended.


\section{Paleogeography}

From Ladinian to Norian times, the paleogeography of the Arabian shelf
was dominated by transitional environments (coastal plain to
shallow-marine shelf) and mixed carbonate--clastic--evaporite sediments
\citep{Glintzboeckel1981,LeNindreetal1990a,Murris1981,Ziegler2001}. In
the western area of the shelf, fine-grained clastics were deposited
(``shale'': siltstone and claystone with some anhydrite), while mixed
carbonates and evaporites dominated in the Gulf area. The main events
in proximal areas were: deposition of marginal marine deposits with
evaporites during the Anisian, influx of continental clastic to the
shelf during the Julian and during the Norian (Lower Minjur Sandstone).
Marine transgressions occurred during the Ladinian (Tr50), Late Julian
(Tr60) and Tuvalian (Tr70), and to a less extent, during the early
Alaunian (Tr80) resulting in deposition of marine carbonates. When
compared to sections located in the south, the relative abundance of
fauna collected from sections now located further north bears witness
to the fact that marine conditions persisted for longer in the north
than in the south, and this argues in favour of connections with an
open-sea environment to the north (outcrop belt is oblique on the
general paleogeographic trends).



\subsection{Connection with the Sephardic Province during the Ladinian}
\label{sec5.1}


The Early Triassic global paleogeographic setting [Figure~\ref{fig10},
modified after \citealp{Scotese2001}, and \citealp{Blakey2003}] shows
the location of the Arabian Plate on the margin of the Neo-Tethys
Ocean. A configuration of barred platform (Zagros, Qatar Arch) with
stronger marine connectivity from the north had already appeared at
this time.

\begin{figure*}
\includegraphics{fig10}
\caption{\label{fig10}Early Triassic plate-tectonic setting showing the position of
the Arabian Plate (in red) with northward opening of the Central Arabia
Basin [modified from \citealp{Scotese2001}; \citealp{Blakey2003}].}
\end{figure*}

The paleobiogeography of the Ladinian conodonts (Figure~\ref{fig11})
demonstrates the existence of four different associations 
\citep{Dercourtetal2000b,Dercourtetal2000a,VrielynckCros1992,
Vrielyncketal1994}. 

\begin{figure*}
\includegraphics{fig11}
\caption{\label{fig11}Distribution of Ladinian conodonts throughout the
Mediterranean Tethyan domain [palaeogeographical base-map modified 
from \citealp{Dercourtetal2000b,Dercourtetal2000a,BarrierVrielynck2008}].}
\vspace*{-6pt}
\end{figure*}

A major one---Tethyan type---is restricted to open-marine areas in
which the sequences of the northern (Alpine), western (Dinarids,
Hellenids), and southern (Taurids) margin were deposited; this pelagic
association is also encountered in the facies of the eastern Neo-Tethys
as far and beyond as Japan. 


The other three associations are encountered in relatively
shallow-water facies in (1) Germany, (2)~the Sephardic Province, and
(3) the Balkans. Geographic separation may account for the differences
between conodont associations in the Germanic and Sephardic provinces.
The specificity of the Balkan shelf is seen as due to its isolation
from the Laurasian Plate. An oceanic buffer (the Paleo-Tethys Ocean)
may be invoked, having been more substantial during the Ladinian than
during the Pliensbachian \citep{Kazminetal1986,Ricouetal1985,Ricouetal1986}.


For the Ladinian, among the species collected in this study, forms
belonging to the genus \textit{Pseudofurnishius} are characteristic of
the Sephardic Province defined by \citet{Hirsch1972}, whereas pelagic
Tethyan type conodonts 
\citep{Bender1967,Gedik1975,Krystyn1983,Krystyn2008,Vrielynck1980,Vrielynck1987}
are missing. The observed Sephardic biofacies thus appears to be
associated with sedimentary conditions such as salinity, water depth
(shallow platforms surrounding the Neo-Tethys), and temperature 
or---as envisaged by \citet{Tollmann1984}, and
\citet{TollmannKristanTollmann1985}---the presence of anti-clockwise
currents bounding emergent sectors of the African Plate and hampering
colonization of the Arabian shelf by open-sea fauna.


During the Carnian and Norian, the Sephardic and Tethyan conodont
provincialism either disappears or has yet to be identified.


\citet{Kearetal2010a,Kearetal2010b} come to a similar conclusion given
by the vertebrate assemblages collected from the lower Jilh Unit 1 of
which affinities reflect the close proximity of the Arabian region to
the Sephardic Province, characterized by a distinct faunal composition.
This thesis was developed above in the section ``Discussion of Ages''
with more emphasis on genera and species present.


\subsection{Jilh time-evolution in the paleogeography of the Arabian Plate}

\citeauthor{Glintzboeckel1981} [\citeyear{Glintzboeckel1981}, BRGM
internal report] drew a series of palaeogeographic maps of Saudi Arabia
that included the Middle to Late Triassic stratigraphy described
herein. \citet{Ziegler2001} drew, with the input of two of the present
authors (YML and DV), two paleogeographic maps corresponding to the
Middle to Late Triassic, although still without the full benefit of our
current stratigraphic understanding, in particular the importance of
the Late Carnian to Early Norian hiatus. In detail Ziegler's two maps
depicted composite representations of:
\begin{itemize}
\item the paleofacies of the Middle Triassic spanning the deposition of
the Jilh Formation and of its regional equivalents from MFS Tr40 to
intra- Tr60 (his figure~5);
\item the paleofacies of the Late Triassic spanning the deposition of
the Upper Jilh and of the Minjur Sandstone from MFS Tr60 to intra-MFS
J10 (his figure~6). It can be argued that this latter map is more
representative of the Carnian sediments preceding the hiatus in the
northern half of the Arabian Plate (e.g., Carnian evaporites in the
Palmyride Trough), but of the Norian sediments postdating the hiatus in
the southern half, including the outcrops that are the main subject of
the present study.
\end{itemize}

Transposing the facies limits from a N--S section (see
Figure~\ref{fig6}) to these maps highlight the horizontal dynamics and
illustrates the evolution of the transgressions from Ladinian to Norian
as visible in the Jilh Formation outcrops, and thus after truncation by
the pre-Minjur unconformity (Figure~\ref{fig12}).

\begin{figure*}
\includegraphics{fig12}
\caption{\label{fig12}Extent of the main sedimentary events of the Jilh Formation,
from Ladinian to late Julian in chronologic order, as in outcrop, and
inferred under the early Norian--pre-Minjur unconformity. Base map
modified after \citet{Ziegler2001} by permission of GeoArabia, with
contribution of \citet{LeNindreetal1990a} for the outcrop. Legend for
outcrop, see Figure~\ref{fig1}.}
\end{figure*}


During the Ladinian and the Lower Carnian (Figure~\ref{fig12}), it
illustrates the difference of trends between the clastic inputs
(towards the northeast) and the marine incursions (from the north),
consistent with the migration of Ladinian conodonts from the Sephardic
Province. (See Section~\ref{sec5.1}. ``Connection with the Sephardic
Province during the Ladinian'' above). Evaporitic pans are concentrated
in the Central Arabian Basin. The first stage of transgression
corresponds to the southward extent of the Ladinian tidal flats (1)
associated with MFS Tr50. Then, during the Early Carnian, clastic
wedges prograded from the shelf (2 in Figure~\ref{fig12}). During the
Julian, the shallow-marine facies (3) achieved their maximum extent
southward (23\textdegree 30$'$~N) since the Ladinian; meanwhile
generalized tidal flats (mixed or carbonated) capped the clastics
further south up to 22\textdegree~N (4, MFS Tr60, Figure~\ref{fig12}).
\citet{Glintzboeckel1981} depicted more common evaporites in the Gulf,
while marine \mbox{carbonates} occupied a broader surface in the north central
area, whereas \citet{Ziegler2001} maps a mixed evaporites and shallow
marine carbonate shelf which is more consistent with our present
knowledge. In a further difference between the two accounts, Ziegler
maps shallow marine carbonates and clastics in the Rub al Khali Basin,
while Glintzboeckel extended evaporites into this basin, which is
principally true during the Anisian, and partially true during the
Carnian \citep{DevilledePeriereetal2022}. 


During the Tuvalian and the Norian (Figure~\ref{fig13}), the general shape we
give to the transgressive wedges is inspired from the tongue of
``Marginal-marine to shallow-marine clastics'' (Baluti Formation
facies) which penetrates the ``continental deposits'' during the
Norian.

\begin{figure*}
{\vspace*{-1pt}}
\includegraphics{fig13}
{\vspace*{-1pt}}
\caption{\label{fig13}Extent of the main sedimentary events of the Jilh Formation,
from late Julian to Middle Norian in chronologic order, as in outcrop,
and inferred under the early Norian--pre-Minjur unconformity. Base map
modified after \citet{Ziegler2001} by permission of GeoArabia, with
contribution of \citet{LeNindreetal1990a} for the outcrop. For legend of
the Jilh outcrop, see Figure~\ref{fig1}.}
{\vspace*{-1pt}}
\end{figure*}

The Tuvalian transgression (5), likely truncated, reached up to
25\textdegree~N, a little more with tidal flats, and likely up to
23\textdegree 30$'$~N: \citet{Issautieretal2012a} and
\citet{Issautieretal2019} have supposed that the Tuvalian (Tr70) may
have a more southern extension at the base of the ``Minjur
Sandstone'' \textit{sensu}  \citet{Vasletetal1983} at least up to
23\textdegree 30$'$~N with sabkha facies (Sequence 1), and in the near
subsurface upper Jilh of the well 143-3 (Palynozone T2-A,) but any more
southerly extent was truncated by the Carnian--Early Norian unconformity
(SB2, Figure~\ref{fig9}). The Norian marine deposits (Tr80) reached
more or less 25\textdegree 30$'$~N southward in the Jilh Formation
while tidal flats and local tidal inlet are identified up to
23\textdegree 30 in the \mbox{Minjur} Formation. The Ladinian to Norian
transgressive pulses appear with the marine influences progressively
regressing northwards in relative to the central evaporitic basin. This
Norian paleogeography is consistent with the global Neo-Tethys
reconstruction for this period of  \citet{BerraAngiolini2014}.

\begin{figure*}
{\vspace*{-3pt}}
\includegraphics{fig14}
{\vspace*{-3pt}}
\caption{\label{fig14}Overall chronostratigraphic chart of the Late Permian to Mid
Toarcian time interval. MFS modified after \citet{DaviesSimmons2018};
Permian and Triassic depositional units after \citet{LeNindreetal1990b}
and \citet{Vasletetal2005}; palynozones after \citet{Issautieretal2019}
and \citet{DevilledePeriereetal2022}. 
(PKU: Pre-Khuff unconformity; END: Early Norian disconformity; PMiU:
Pre Minjur unconformity; MRU: Mid Rhaetian unconformity; LDoU?/PMaU:
Domerian/Pre-Marrat unconformity; LToD: Late Toarcian disconformity;
AaCi (Fe): Aalenian condensed interval.)}
{\vspace*{-2pt}}
\end{figure*}


\section{Conclusions}

\begin{enumerate}[(1)]
\item New correlations within the Jilh Formation and the Minjur
Sandstone in outcrop and subsurface highlight geometric and
chronostratigraphic aspects of the Middle--Late Triassic in Saudi
Arabia. 

\item Five main marine flooding intervals characterizing the late
Mid--Late Triassic Epochs were demonstrated from outcrops on the
western margin of the Arabian shelf. It is likely that the Anisian
tidal flats deposits represent the MFS Tr40. The other marine flooding
events are well constrained by marker faunas: Ladinian MFS Tr50, late
Julian (Early Carnian) MFS Tr60, Tuvalian (Late Carnian) MFS Tr70, and
early Alaunian (Mid Norian). Different populations of Ladinian
conodonts in stratigraphically equivalent horizons are explained by
environmental factors, instead of age differences. Lacian rocks are
probably absent owing to erosion beneath the combined Late Carnian to
Early Norian and Early to Middle Norian unconformities [SB2 and SB4
respectively, of \citealp{Issautieretal2012a,Issautieretal2019}]. The
Alaunian MFS (S4 MFS) is, dated by \textit{Tibetitidae} and the
\textit{Ancyrogondolella praeslovakensis} faunas, north of Lat.
25\textdegree~N, in correspondence with the \textit{Rhaetogonyaulax
wigginsii} palynosubzone of the middle Minjur. It is tentatively
assigned to ``Tr80'' in Central Arabia. An alternative definition of
``Tr80'' exists in Musandam in the Milaha Formation
\citep{DaviesSimmons2018}, but the most recent results from that
section \citep{Urbanetal2023} appear to favour a similar Middle Norian
age for this MFS, with a Late Norian age for the overlying sequence in
the Ghalilah Formation (MFS Tr90?). 

\item Truncations separating the packages could be invoked at the base
of the Julian clastics (base Unit J2), at the base of the Late Julian
transgression (TSF, Time Specific 
Facies---\citealp{Brettetal2012,PaviaMartire2015}---with Fe oolites) on top of paleosols, and between the Carnian and the
Norian. These are candidates for plate-wide sequence boundaries (Tr60
SB, Tr70 SB and Tr80 SB). The nature of the boundary between the
Anisian and the Ladinian is not definitively resolved at the regional
scale.

\item The boundary between the Jilh Formation and the Minjur Sandstone
[SB2 of \citealp{Issautieretal2012a,Issautieretal2019}] is sharp, with
an erosional contact in the fluvial portion of the system in central
Arabia near the reference sections. Towards the south, a valley fill
containing tidal inlet, sabkha, and fluvial deposits is identified. An
undated sequence [Minjur Sequence 1 of \citealp{Issautieretal2012a,Issautieretal2012b}]
with sabkha facies previously assigned to the Minjur Sandstone caps the
Julian Jilh Dolomite and underlies these erosional channels. By lateral
correlation we have interpreted these horizons as residual Tuvalian
(T2A palynosubzone). An important finding of this study is
reconstruction of an early Alaunian transgressive wedge, with an
erosive base taken on the sequence boundary (SB4) which had been
correlated from central to north\break Arabia.  


\item {Interfingering of various sediment types, and abrupt changes in
lithology, as at the Ladinian Carnian boundary, are not explained by
sea level changes alone. The deconstruction done, employing multiple
datums, illustrates the role of tectonics, by identifying several
structures active during the sedimentation. This does not exclude a
probable, though possibly minor, role of the climate, including the
Carnian Pluvial Event. This study enables a better understanding of the
complex relationships between carbonate, evaporites and siliciclastic
detrital rocks which are the major characteristic of these Mid--Late
Triassic Epochs. Through a stratigraphic analysis based, not just on
well logs facies correlation but on reliable biostratigraphic studies
in outcrop (to be continued), better regional correlations are made
possible.}

\item The paleogeographic reconstruction first\unskip\break inserts the faunas
collected for the study in a Tethyan paleo-biogeography. Understanding
their migration is a precious aid to  reconstruction of the processes of
transgression and regression at large scale. The lessons learned from
outcrop are now integrated in the Middle East paleogeography of the
Mid--Late Triassic, showing the dynamic keys of the different periods.

\item From the results obtained in Parts I and II of this study,
complemented by previous publications 
\citep[e.g.,][]{DaviesSimmons2018,DevilledePeriereetal2022,Haq2018,
Issautieretal2019,LeNindreetal1990b,LeNindreetal2022,LeNindreetal2023,
Manivitetal1990,Vasletetal2005},
we have derived an overall chronostratigraphic chart spanning this time
interval and expanded to include the Late \mbox{Permian} to Early Triassic
Khuff Formation and Sudair Shale, and the Early Jurassic Marrat
Formation (Figure~\ref{fig14}). The absolute ages are from GTS 2020/03 
[\citealp{Cohenetal2013}, updated 2020]. These results facilitate
correlation throughout the platform, especially where reliable
biostratigraphic markers are present.
\end{enumerate}

\section*{Conflicts of interest}
Authors have no conflict of interest to declare.

{\vspace*{-2pt}}


\section*{Acknowledgments}
The authors thank the Deputy Ministry for Mineral Resources, Kingdom
of Saudi Arabia, for his support to the Phanerozoic Cover Rock Mapping
Program during which most of the field works were performed and for
permission of publishing (BRGM-OF-06-31). The publication of this
Synthesis on the Triassic of Saudi Arabia was made possible through
this Special Publication as a Tribute to Jean Dercourt under the
auspices of the French Acad\'{e}mie des Sciences. Authors are
especially grateful to the editors Fran\c{c}ois Baudin, Sorbonne
Universit\'{e}, Fran\c{c}ois Chabaux, Strasbourg University and Eric
Calais, Ecole Normale Sup\'{e}rieure for their invitation,
encouragement, and support. The authors have special thanks to Augustus
Wilson and Moujahed I. Al-Husseini, former GeoArabia Editor in Chief,
for their constructive comments while writing this paper. The new
decisive results on conodonts from the Qibah area by Leopold Krystyn
were made possible thanks to the support provided by Olivier Serrano,
BRGM. Thanks to James W. Haggart from the Geological Survey of Canada
who very kindly took from his time for providing photos of the original
Tozer's collection of ammonoids in Vancouver, and to Raymond Enay,
for specimens stored in the University Lyon~I, we have now illustration
of this key fauna. The authors are also very grateful to Nino Buhay,
former graphic team of GeoArabia.  We thank the anonymous reviewers
whose insightful comments greatly improved the paper.

\CDRGrant[BRGM]{BRGM-OF-06-31}

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