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Title: Recognition of deep-water benthic assemblages in the fossil record: Taphonomy and community characteristics of Louisiana continental slope petroleum seep assemblages

Chemoautotrophic benthic assemblages associated with petroleum seepage form the only substantial shell accumulations below storm wave base on the northern Gulf of Mexico shelf and slope. Five biofacies are associated with petroleum seepage, dominated respectively by vestimentiferan tubeworms, lucinid, thyasirid and vesicomyid clams and mytilid mussels. The taphonomy of petroleum seep death assemblages includes dissolution as the most pervasive mode of shell alteration. The dominant species in each assemblage reflect the taphonomic signature of the assemblage they dominate. The taphonomic attributes of petroleum seep death assemblages are similar to those of ancient autochthonous benthic assemblages. Paleoecological characteristics representative of cold seep assemblages include: high density-low diversity molluscan assemblages dominated by large individuals, high molluscan biomass concentrations aligned in linear trends, carbons with depleted [delta][sup 13]C values associated with faunally depauperate shales, laminated or massive sedimentary structures, variable articulation frequencies, poor shell preservation, and a trophic structure dominated by one trophic group. The Campanian Tepee Buttes share many paleoecological characteristics with recognized ancient seep assemblages. Methane and hydrogen sulfide-rich fluids from underlying strata were transported along fault conduits to supply a localized nutrient source for lucinid-dominated benthic communities. The Tepee Butte assemblages were dominated by dense accumulations of Nymphalucina occidentalis withmore » moderate to high articulation frequencies. The lucinids probably used H[sub 2]S as a nutrient source. Cold seeps can be recognized in the fossil record, based on criteria developed by the study of modern cold seep death assemblages, because the paleoecological characteristics of cold seep assemblages are very conservative.« less
Authors:
Publication Date:
OSTI Identifier:
5501128
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph.D.)
Publisher:
College Station, TX (United States); Texas A M Univ.
Research Org:
Texas A and M Univ., College Station, TX (United States)
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; 54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; GULF OF MEXICO; SEEPS; LOUISIANA; CONTINENTAL SLOPE; PALEONTOLOGY; BENTHOS; BIOMASS; CLAMS; DISSOLUTION; ECOLOGY; FOSSILS; MUSSELS; PETROLEUM; ANIMALS; AQUATIC ORGANISMS; ATLANTIC OCEAN; CARIBBEAN SEA; CONTINENTAL MARGIN; DEVELOPED COUNTRIES; ENERGY SOURCES; FOSSIL FUELS; FUELS; INVERTEBRATES; MOLLUSCS; NORTH AMERICA; RENEWABLE ENERGY SOURCES; SEAS; SURFACE WATERS; USA 020200* -- Petroleum-- Reserves, Geology, & Exploration; 540210 -- Environment, Terrestrial-- Basic Studies-- (1990-); 580000 -- Geosciences