Exceptional preservation in the Upper Carboniferous Coseley Lagerstätte

Braznell, Laura Jane (2006). Exceptional preservation in the Upper Carboniferous Coseley Lagerstätte. University of Birmingham. Ph.D.

Preview

Braznell2006PhD.pdf
Text - Accepted Version
Available under License All rights reserved.
Download (13MB) | Preview

Abstract

The Late Carboniferous Coseley Lagerstätte of the West Midlands, UK, contains exceptionally preserved plant and animal fossils that occur as hard parts and mineralized soft tissues sealed within siderite concretions. The concretions were recovered from Westphalian B siltstones and mudstones that lie above the Thick Coal of the Coal Measure Group.
The Coseley plant fossils include a diverse range of plant groups including lycopsids, sphenopsids, ferns and pteridosperms. These are found as isolated fragments that include stems, leaves, cones, seeds and pollen sacs. The Coseley animal fossils comprise a diverse assemblage of arthropods that includes xiphosurans, crustaceans, arachnids, hexapods and myriapods, along with fish and molluscs. All of these organisms lived on and within a Coal Measure swamp forest occupying various niches at different trophic levels producing a complex trophic food web.
The Coseley fossils have been examined using various techniques including scanning electron microscopy and electron microprobe analysis that have revealed several phases of bacterially mediated preservation. Early framboidal pyrite growth accompanied decay of very volatile soft tissues, followed by the precipitation of open framework siderite concretions through bacterially mediated methanogenesis. This occurred either as a crystal phase around plant fossil or as a biofilm around animal ones and prevented compaction of the fossils. Bacterially induced void filling kaolinite mineralization then preceded the secondary phase of siderite precipitation which was then followed later on by void filling sphalerite, galena and pyrite sulphide mineralization, and carbonate mineralization.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):