Abstract

An upper Campanian to upper Oligocene stratigraphic succession has been examined from six deep exploration wells in the Palmyrides area of Syria. Most of the sedimentary succession contains rich and well to moderately preserved planktonic foraminiferal assemblages that enable successful age determination. The upper Campanian and Maastrichtian planktonic fauna is highly diverse with domination of warm water taxa such as Globotruncana aegyptiaca, Gansserina gansseri, Globotruncanella havanensis, Globotruncanita angulata and Pseudotextularia elegans. The most dramatic turnover occurred across the Cretaceous/Palaeocene boundary when most planktonic foraminiferal species became extinct. The oldest Palaeocene planktonic foraminiferal assemblage, rich in the number of specimens, but not very diverse, includes the following species: Eoglobigerina eobulloides, Globanomalina archeocompressa, Chiloguembelina morsei, Woodringina claytonensis and Parasubbotina pseudobulloides. The late Palaeocene is marked by origination of the morozovellids, acarininids and globanomalinids, while the early Eocene is characterized by a tropical assemblage, dominated by muricate species, and by intensive speciation of Acarinina and Subbotina in the latest part. Most of these species continue into the middle Eocene and become a significant component of the planktonic community. The middle Eocene is characterized by intensive speciation and domination of warm water genera such as Acarinina, Morozovelloides, and to a lesser degree Turborotalia, Globigerinatheka and Hantkenina. The middle/late Eocene boundary is marked by double extinction of the last muricate taxa Acarinina mcgowrani and Morozovelloides crasssatus, which indicate a variable climate, water column instability, and loss of surface habitats. In contrast, Turborotalia and Globigerinateheka become more important in the late Eocene. The Eocene/Oligocene boundary is marked by the extinction of most warm water taxa including Turborotalia cerroazulensis group, Hantkenina, Globigerinatheka and some subbotinids. The beginning of the early Oligocene is indicated by the domination of cool water taxa such as Dentoglobigerina, Globorotaloides, Tenuitella and Chiloguembelina. Speciation of the spinose surface dweller Ciperoella ciperoensis group reflects warming in the late Oligocene. The combined observations of lithology with the diversity and composition of planktonic foraminifera assemblages indicate that the Palmyrides area in Syria was a Tethyan bioprovince with a tropical to subtropical climate from the late Campanian to the end of the Eocene with deposition in deep sea environments (upper bathyal to outer shelf). In contrast, Oligocene deposits and their microfossil content suggest temperate to warm climate conditions and sedimentation in middle to inner shelf environments.

Highlights

  • Upper Cretaceous and Palaeogene deposits drilled in six deep exploration wells in the Palmyrides, Syria comprise an approximately 1300 metre thick succession of marine strata

  • This study focused on the rich, well-preserved and diverse planktonic foraminiferal assemblages found in upper Cretaceous to upper Oligocene deposits from exploration wells in the Palmyrides area of Syria

  • Global palaeoenvironmental changes are reflected in the composition, speciation and extinction of the examined planktonic foraminiferal population

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Summary

Introduction

Upper Cretaceous and Palaeogene deposits drilled in six deep exploration wells in the Palmyrides, Syria comprise an approximately 1300 metre thick succession of marine strata These deposits are predominantly composed of hemipelagic argillaceous limestones and marls (upper Cretaceous), deep water clayey limestones and marls (Palaeocene and Eocene), and sandstone, bioclastic limestone and marls (Oligocene). Morphological characteristics of the tests (shape and size, wall texture, etc.) are usually developed as a response to the biotic and abiotic requirements of their natural habitats. These characteristics allow differentiation of four main upper ocean (i.e., photic zone) habitats: surface/subsurface, mixed-layers, thermocline and subthermocline. This study documents the composition, changes and frequency of the main planktonic foraminiferal groups during the geological time period spanning the late Campanian to the end of the Oligocene

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