Late Triassic mollusk-dominated hydrocarbon-seep deposits from Turkey.

Author(s)

Steffen Kiel, Leopold Krystyn, Ferdi Demirtas, Erdal Kosun, Jörn Ludwig Peckmann

Abstract

Deep-sea hydrothermal vents and hydrocarbon seeps host unique ecosystems relying on geochemical energy rather than photosynthesis. Whereas the fossil and evolutionary history of these ecosystems is increasingly well known from the Cretaceous onward, their earlier history remains poorly understood and brachiopods are considered to have played a dominant role during the Paleozoic and Mesozoic. Here we report five new hydrocarbon-seep deposits from the Upper Triassic Kasimlar shales in southern Turkey. The pyritiferous seep limestones predominantly consist of

¹³C-depleted micrite with δ

¹³C values as low as -10.4‰, and contain only sparse

¹³C-depleted rim cement (δ

¹³C as low as -12.0‰), interpreted to result from the recrystallization of banded and botryoidal crystal aggregates of fibrous cement. The geologic ages of the studied seep deposits were determined as late Carnian and early Norian using conodonts. The associated fauna is dominated by modiomorphid and anomalodesmatan bivalves, and also includes a diversity of gastropods and the dimerelloid brachiopod Halorella. These faunal assemblages allow a comparison between seep faunas from the two major Triassic ocean basins-the present assemblages being from Tethys, and the only previously known examples being from eastern Panthalassa-and indicate that a cosmopolitan, seeprestricted fauna as in the present-day oceans has existed since the Late Triassic. With almost 20 species, the seep fauna of the Kasimlar shales approaches the diversity of Cretaceous to present-day seep faunas, further emphasizing the ecological similarity of seep faunas since the early Mesozoic. Our findings also highlight that brachiopods and bivalves had a more complex history of coexistence at seeps than currently appreciated.

Organisation(s)

Department of Palaeontology

External organisation(s)

Swedish Museum of Natural History, Akdeniz University, Universität Hamburg

Journal

Geology

Volume

45

Pages

751-754

No. of pages

4

DOI

https://doi.org/10.1130/G39259.1

Publication date

2017

Peer reviewed

Yes

Austrian Fields of Science 2012

105101 General geology, 105118 Palaeontology

Keywords

ASJC Scopus subject areas

Geology

Portal url

https://ucrisportal.univie.ac.at/en/publications/0d5db815-66e3-47a2-8e03-96fb0cb1f4d4