Raisossadat, Seyed Naser;
(2002)
Lower Cretaceous (Upper Barremian-Lower Albian) ammonite faunas of the Kopet Dagh Basin, NE Iran.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The Kopet Dagh basin is situated in the north-east of Iran. The ammonite faunas of the Sarcheshmeh and Sanganeh Formations have been studied. Ten stratigraphic sections have been measured and sampled. Species of Heteroceratidae, Ancyloceratidae, Deshayesitidae, Parahoplitidae, Douvilleiceratidae, Desmoceratidae and Oppeliidae are described, some new to the basin. The faunas are of Late Barremian to Late Aptian age. Previous records of Early Albian forms are reviewed. A Lower Cretaceous ammonite biozonation for the Kopet Dagh Basin is proposed and can be correlated to the standard Mediterranean biozonation in most sub-stages. The ammonite faunas are grouped into four morphogroups. Study of the distribution of the shell morphogroups in relation to lithofacies indicates that facies and associated sea-level changes played a significant role in the distribution of ammonites in the basin. The Parahoplitidae and Deshayesitidae, both with ornamented shells, lived in medium to high energy environments, while the smooth-shelled Desmoceratidae and Oppeliidae preferred quieter conditions. The effects of two significance sea-level rises and many minor ones can be traced in the Sarcheshmeh and Sanganeh Formations. In most cases, genera or species first appear in the basin in transgressive and highstand systems tracts. The palaeobiogeographical relationships of the ammonites indicate that during the Late Barremian to Upper Aptian the basin formed part of the Mediterranean-Himalayan Province, but in the latest Aptian and Albian was open to Mediterranean-Caucasian faunas. The ammonite faunas coupled with the palaeogeographical position of the basin at the northern margin of Tethys indicate a close relationship with the Caspian and Caucasian regions.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Lower Cretaceous (Upper Barremian-Lower Albian) ammonite faunas of the Kopet Dagh Basin, NE Iran |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| Keywords: | Earth sciences; Ammonites; Iran |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10104689 |
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