Stratigraphy, ichnology, and sedimentary environments of the Late Bajocian, Late Bathonian Kashafrud Formation, Northeastern Iran [Elektronische Ressource] / vorgelegt von Jafar Taheri

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• Publié par: julius-maximilians-universitat_wurzburg
• Publié le: 01 janvier 2009
• Nombre de lectures: 35
• Langue: English
• Poids de l'ouvrage: 99 Mo

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Stratigraphy, ichnology, and sedimentary environments of the Late Bajocian-Late Bathonian
Kashafrud Formation, Northeastern Iran 1




Stratigraphy, ichnology, and sedimentary environments of the Late Bajocian-Late Bathonian
Kashafrud Formation, Northeastern Iran 2





To my parents,
Who have given me a precious gift named “life”.
I’ll always be grateful to them.

To my thoughtful (kind-dear) wife
For her dedication during my studies,
For her; who patiently accepted unavoidable problems,
For being my eternal companion step by step during of my life.

And to my children,
Who according to our culture, should have a tranquil father for supporting
them during the best period of their life,
and with hope for them to create greater success for themselves and their
community.








Stratigraphy, ichnology, and sedimentary environments of the Late Bajocian-Late Bathonian
Kashafrud Formation, Northeastern Iran 3


Acknowledgments
I acknowledge financial support by the German Research Society (Deutsche
Forschungsgemeinschaft), grant FU 131/32. I thank In particular, my supervisor, Prof. F.T.
FÜRSICH, who provided the opportunity to study in Würzburg. I benefitted from his valuable
discussions, critical review and constructive comments on the manuscript. I also appreciate the
help, hospitality, and kindness of his family toward my family during our stay in Würzburg. Prof.
Dr. M. WILMSEN had an effective role in scientific discussions and interpretation of the data. I
appreciate his helpful comments, and valuable discussions.
I also would like to thank the staff of the Institut für Paläontologie und Geologie der Universität
Würzburg, Prof. H. DE WALL, and Dr. M. HEINZE for their help and Mrs. H. SCHÖNIG, for precise
photographic work.
I thank to Prof. K. SEYED-EMAMI (Tehran University), for his precious discussions and
determination of some of the ammonites. I would like to thank, M. HOSAINIUN and Dr. M.
MAJIDIFARD for their help and determination of ammonites which have collected from the
Kashafrud Formation.
I am grateful to Dr. B. NIEBUHR (SARAH), for help in the field of some software and kindness
towards my family. My appreciation goes to M. T. KOREIE, Head of the Geological Survey of
Iran, and to Dr. M. MEHR PARTOW, past exploration Deputy, for their full support, to J.
ROWSHANRAVAN, the present head of Mashhad GSI, for his organization of field trips, and to my
co-workers at GSINET (Geological Survey of Iran, North-East Territory) for their help in
fieldwork in Iran.
And, finally, I am indebted to all teachers who contributed to my education, from the first stage
to the present one; I would like to thank them for all their kindness and……





Stratigraphy, ichnology, and sedimentary environments of the Late Bajocian-Late Bathonian
Kashafrud Formation, Northeastern Iran 4


Abstract. The Upper Bajocian-Bathonian Kashafrud Formation is a thick package of
siliciclastic sediments that crops out in NE Iran from the southeast, near the Afghanistan
border, to north- northwestern areas around the city of Mashhad. The thickness ranges from
less than 300 m in a deltaic succession (Kuh-e-Radar) to more than 2500 m in the Maiamay
area, but the normal thickness in Ghal-e-Sangi, Kol-e-Malekabad, and Fraizi areas is about
1200-1300 m. It is the fill of an elongated basin, which extended for more than 200 km in
NW-SE direction and a width of at least 50 km along the southern margin of the Koppeh
Dagh.
Prior to this study, little information existed about the sedimentary environments and other
characters, especially the geometry of the basin. Exact biostratigraphic data from the top of
the Kashafrud Formation were rare. Based on the macrofauna from the lower part of the
overlying Chamanbid Formation the upper boundary of the Kashafrud Formation had been
attributed to the ?Late Bathonian and/or Early Callovian, but now the upper limit of the
Kashafrud Formation is defined as Late Bathonian in age, based on ammonite biostratigraphy.
Except for chapter one, which deals with the introduction and related sub-titles, in the
following chapters, step by step, field observations and data were surveyed according to the
questions to solve.
In order to reconstruct the facies architecture and the geometry of the basin, a number of
sections have been logged in detail (see chapter 3, “The sections”). The exact biostratigraphic
setting is discussed in chapter 4 (“Biostratigraphy”).
Sedimentary environments range from non-marine alluvial fans and braided rivers in the basal
part of the succession to deltas, storm-dominated shelf, slope and deep-marine basin. The
latter comprises the largest part of the basin fill, consisting of monotonous mudstones,
siltstones and proximal to distal turbidities. The only continuous carbonate unit (~30 m)
locally formed at Tappenader. Other localities in which thin fossil-bearing carbonate strata
occur are Torbat-e-Jam (benthic fauna) and, to a lesser extent, Ghal-e-Sangi. These rare
shallow-water carbonates, which also contain corals, represent only short intervals (see
chapter 5,” Facies association and sedimentary environments”).
Relative changes in sea level were reconstructed on the basis of deepening- and shallowing-
upward trends. Sequence boundaries and parasequences have been distinguished and analyzed
in chapter 6 (“Sequence stratigraphy”). In most areas, the basin rapidly evolved from a
shallow marine, transgressive succession to a deep-marine, basinal succession. The only area
Stratigraphy, ichnology, and sedimentary environments of the Late Bajocian-Late Bathonian
Kashafrud Formation, Northeastern Iran 5


where shallow conditions persisted from the Late Bajocian to the Late Bathonian, and even
into the Early Callovian is the Kuh-e-Radar area which corresponds to a fan-delta setting.
A trace fossil analysis has been carried out to obtain additional evidence on the bathymetry of
the basin (see chapter 7, “Ichnology”). Altogether 29 ichnospecies belonging to 15
ichnogenera have been identified, as well as 10 ichnogenera, which were determined only at
genus level. They can be grouped in the well-known “Seilacherian ichnofacies”.
Very high subsidence rates and strong lateral thickness variations suggest that the Kashafrud
Formation is a rift related basin that formed as the eastern extension of the South Caspian
Basin. The basin evolution is reviewed, the eastern and western continuations of the basin
were checked in the field and also in the literature (see chapter 8, “Basin evolution”).
In all, the present study provided new insights into the development of the Kashafrud
Formation, e.g. more biostratigraphic data from the base and the top of the succession, a
relatively complete picture of the trace fossil associations, a better recognition and
reconstruction of the sedimentary environments in different parts of the basin. Finally this
research project will be a good basis for further investigations, especially towards the west, as
parts of the Kashafrud Formation are source rocks of a hydrocarbon reservoir in NE Iran.





















Stratigraphy, ichnology, and sedimentary environments of the Late Bajocian-Late Bathonian
Kashafrud Formation, Northeastern Iran 6


Contents

1. Introduction ……………………………………………………………………….7
1.1 Geological setting ……………………………………………………………….8
1.2 Stratigraphy ……………………………………………………………………..14
1.3 Localities …………………………………………………………………….....16
1.4 Purposes of study …..17
2. Materials and methods ………………………..…………………………………19
3. The sections ……………………………………………………………………....27
4. Biostratigraphy …….91
5. Facies associations
5.1 Preface …………..100
5.2 Alluvial fans and braided rivers ……………….……………………………....101
5.3 Delta sub-environments ……………………………………………………….108
5.4 Shelf environments ………………...………118
5.5 Deep-Sea successions ………...…..…………………………………………...119
6. Sequence stratigraphy ………………………………………………………….134
7. Ichnology
7.1 Preface ………………………………………………………………………...144
7.2 Ichnotaxonomy ….144
7.3 Ichnofacies ………………………………………………………………….…181
8. Basin evolution ………………………………………….………………………211
9. Conclusions ……….…223
10. References ……….232
Stratigraphy, ichnology, and sedimentary environments of the Late Bajocian-Late Bathonian
Kashafrud Formation, Northeastern Iran 7


Introduction
The name Kashafrud Formation started to appear in the