Early Cretaceous giant bivalves from seep-related limestone mounds, Wollaston Forland, Northeast Greenland
Published:January 01, 2000
Simon R. A. Kelly, Eric Blanc, Simon P. Price, Andrew G. Whitham, 2000. "Early Cretaceous giant bivalves from seep-related limestone mounds, Wollaston Forland, Northeast Greenland", The Evolutionary Biology of the Bivalvia, E. M. Harper, J. D. Taylor, J. A. Crame
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Anomalous mound-forming limestones, here termed the Kuhnpasset Beds, occur within Late Barremian (Early Cretaceous) mudstones on Wollaston Forland, Northeast Greenland. The normal mudstones contain a sparse fauna of small nuculoids, arcoids and inoceramids; by contrast, the mounds contain an unusual faunal assembage, dominated by large bivalves. These include an abundant lucinid, Cryptolucina kuhnpassetensis sp. nov., and, less commonly, Solemya, both known seep-associated genera. Locally, a large modiomorphid, Caspiconcha whithami gen. et sp. nov., is common and reaches > 300 mm in length and has a shell up to 28 mm thick. Also, the wood-boring bivalve Turnus is abundant in driftwood. Gastropods are rare, but the associated cephalopod fauna includes ammonites, belemnites, nautiloids and a remarkable large orthoconic phragmocone. The form of the mounds with calcite-cemented tube systems, associated laminated calcite crusts and void fills, together with the fauna, is analogous to those of methane-based cold-seep complexes. However, preliminary studies indicate that much of the original aragonitic shell is now replaced by silica. This precluded conclusive geochemical studies based on the shells themselves. It is believed that the mounds formed on the seafloor in a mid- to outer shelf situation at the end of a period of extensional rifting on the eastern Greenland passive Atlantic margin. The vents occur near the footwall crest of a tilted fault block. The underlying faults may have provided routes or influenced direction of movement for nutrient migration. Source rocks were probably the Late Jurassic black shales from depths of < 600–1200 m. If methane was being generated, it was probably forming by shallow-depth organic breakdown rather than by thermogenic processes, which require greater burial.
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The Evolutionary Biology of the Bivalvia
Bivalves are key components of Recent marine and freshwater ecosystems and have been so for most of the Phanerozoic. Their rich and long fossil record, combined with their abundance and diversity in modern seas, has made bivalves the ideal subject of palaeobiological and evolutionary studies. Despite this, however, topics such as the early evolution of the class, relationships between various taxa and the life habits of some key extinct forms have remained remarkably unclear.
In the last few years there has been enormous expansion in the range of techniques available to both palaeontologists and zoologists and key discoveries of new faunas which shed new light on the evolutionary biology of this important class.
This volume integrates palaeontological and zoological approaches and sheds new light on the course of bivalve evolution. This series of 32 original papers tackles key issues including: up to date molecular phylogenies of major groups; new hard and soft tissue morphological cladistic analyses; reassessments of the early Palaeozoic radiation; important new observations on form and functional morphology; analyses of biogeography and biodiversity; novel (palaeo)ecological studies