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Unravelling ophiolite emplacement history with microfossils - the Baer-Bassit ophiolite of NW Syria

Howard, DP; (2006) Unravelling ophiolite emplacement history with microfossils - the Baer-Bassit ophiolite of NW Syria. Doctoral thesis , UCL (University College London). Green open access

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Abstract

The Baer-Bassit ophiolite of NW Syria is one of a number of ophiolites that form a chain from Cyprus in the West to Oman in the East. Micropalaeontological analyses of samples collected from the Baer-Bassit area reveal details of the various stages of evolution of the ophiolite as well as the Arabian continental margin. Interpillow sediments and cements proved to be barren of any microfauna or microflora, unlike comparable sediments from the Cyprus Troodos ophiolite, therefore no age of formation of the ophiolite can be inferred. Campanian age sediments from the autochthonous carbonate platform structurally beneath the ophiolite are here reported for the first time, and are dated by the presence of zonal radioalaria including Amphipyndax pseudoconulus and Foremanina schona. Planktonic foraminifera including Globotruncana calcarata also indicate a Campanian age for the sediments immediately beneath the overlying ophiolite. The youngest autochthonous sediments are perhaps earliest Maastrichtian, but although no specific marker taxa were recovered the overall assemblages from these samples indicate a Campanian age is more likely. Immediately prior to ophiolite emplacement southwards onto the Arabian continental margin, an increase in water depth, reflected in the microfossil assemblages recovered, perhaps signalled flexural loading of the continental shelf by the approaching ophiolitic nappes. After emplacement the ophiolite was emerged and eroded for a short time (c 2-3Ma) before being transgressed during the latest Campanian - earliest Maastrichtian. Shallow water sandstones and conglomerates, with common larger benthic foraminifera were then locally deposited for a short time before pelagic sedimentation was re-established. The dating of the sediments structurally beneath and overlying the ophiolite limits the age of emplacement of the Baer-Bassit ophiolite to the latest Campanian - earliest Maastrichtian. The deposition of pelagic carbonates continued until the latest Maastrichtian. The Cretaceous-Tertiary boundary is marked by a sedimentary hiatus spanning planktonic foraminiferal zones Pa, PO and PI a. There is no visible change in lithology between the Cretaceous and early Tertiary sediments with both consisting of monotonous marls and marly limestones. Reworked Cretaceous foraminifera occur commonly in the Danian sediments, sometimes dominating assemblages, particularly within sediments dated as belonging to the Pic Globanomalina compressa/Praemurica inconstans- Praemurica uncinata Interval Subzone. Pelagic carbonate sedimentation then continued until the Upper Eocene, when regional tectonics (suturing of the Eurasian and Arabian plates) caused syn-depositional deformation as well as regional uplift, reflected in the depositional of nummulitic limestones.

Type: Thesis (Doctoral)
Title: Unravelling ophiolite emplacement history with microfossils - the Baer-Bassit ophiolite of NW Syria
Identifier: PQ ETD:592966
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/1445642
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