Late Carboniferous hydrocarbon-seep carbonates from the glaciomarine Dwyka Group, southern Namibia

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作   者：

Himmler T;  Freiwald A;  Stollhofen H;  Peckmann J; 

作者机构：

Germany;  Inst Geol;  D-91054 Erlangen;  Univ Erlangen Nurnberg;  Res Ctr Ocean Margins;  Univ Aachen;  D-28334 Bremen;  D-52056 Aachen;  Inst Palaeontol;  Univ Bremen; 

关键词：

OXIDATION;  MOROCCO;  Pennsylvanian;  DEPOSIT;  WESTERN WASHINGTON-STATE;  SEA;  vestimentiferans;  HOLLARD MOUND;  Karoo;  HYDROTHERMAL VENT;  EVOLUTION;  METHANE-SEEPS;  methane;  COLD-SEEPS;  hydrocarbon seeps; 

期刊名称：

Palaeogeography, Palaeoclimatology, Palaeoecology: An International Journal for the Geo-Sciences

i s s n：

0031-0182

年卷期：

2008 年 257 卷 1/2 期

页   码：

185-197

页   码：

摘   要：

Limestone deposits with columnar to lenticular geometry (max. 3.2 m in height and 1.5 m in diameter) occur within the uppermost part of the Ganigobis Shale Member, a marine mudstone unit capping the second deglaciation sequence of the glaciomarine Dwyka Group in southern Namibia. The limestones mainly consist of four authigenic carbonate phases (microspar, banded/botryoidal cement, yellow calcite, spheroidal calcite). Extremely negative delta C-13 values (as low as -51%o VPDB) indicate a hydrocarbon-derived origin of the carbonates with biogenic methane being the most likely carbon source. The limestones contain a low-diversity but high-abundance faunal assemblage of tubular fossils. These fossils closely resemble the tubes of modem and fossil seep-dwelling vestimentiferan tube worms in terms of size, shape, arrangement, and taphonomical patterns. (C) 2007 Elsevier B.V. All rights reserved.