GEOCHEMICAL CONTROLS ON CARBONATE SHELL TAPHONOMY IN NORTHERN GULF OF MEXICO CONTINENTAL SHELF AND SLOPE SEDIMENTS

被引:9
|
作者
Powell, Eric N. [1 ]
Hu, Xinping [2 ]
Cai, We-Jun [2 ]
Ashton-Alcox, Kathryn A. [1 ]
Parsons-Hubbard, Karla M. [3 ]
Walker, Sally E. [4 ]
机构
[1] Rutgers State Univ, Haskin Shellfish Res Lab, Port Norris, NJ 08349 USA
[2] Univ Georgia, Dept Marine Sci, Athens, GA 30602 USA
[3] Oberlin Coll, Dept Geol, Oberlin, OH 44074 USA
[4] Univ Georgia, Dept Geol, Athens, GA 30602 USA
基金
美国国家科学基金会; 美国海洋和大气管理局;
关键词
MOLLUSCAN DEATH ASSEMBLAGES; HYDROCARBON SEEP COMMUNITIES; CHEMOSYNTHETIC COMMUNITIES; PALEOCOMMUNITY RECONSTRUCTION; POPULATION-DYNAMICS; OCEAN ACIDIFICATION; FOSSIL ASSEMBLAGES; LARVAL SETTLEMENT; BIVALVE TAPHONOMY; CALCIUM-CARBONATE;
D O I
10.2110/palo.2011.p11-116r
中图分类号
P5 [地质学];
学科分类号
0709 ; 081803 ;
摘要
We examine the linkage between the sediment geochemical milieu and the process of carbonate degradation over a wide range of continental shelf and slope sediments using molluscan shells deployed for 13 years by the Shelf and Slope Experimental Taphonomy Initiative (SSETI). Geochemical characterization of the environment of preservation included the breadth of the pore-water carbonate undersaturation window, a depthintegrated carbonate dissolution index, the depth of minimum pore-water saturation, diffusive fluxes of oxygen and calcium, average sulfate and chloride concentration in the upper 5 cm, and the carbonate and organic carbon fractions in the same sedimentary horizon. Taphonomic indices included the maximum degree of dissolution; average dissolution; the incidences of chalkiness, pitting, deep dissolution, and a soft shell surface; the maximum degree of discoloration; the incidences of fading, gray-to-black discoloration, brown discoloration, and orange discoloration; the presence of pyrite; and edge rounding. Geochemical variables characterize the extent of most taphonomic processes with high three-variable multiple regression coefficients (R-2 > 0.85). Dissolution was most intense at petroleum seeps where enhanced sediment respiration fueled by petroleum carbon and oxidation of reduced species (e.g., H2S) resulted in acute porewater carbonate undersaturation near the sediment-water interface and high diffusive oxygen flux. In contrast, discoloration occurred as often or more commonly in shelf and slope sediments that were not subject to seep influence. The tendency for correlations between many taphonomic metrics, including those relating to dissolution, pyritization, and discoloration, and the breadths of the calcite/aragonite undersaturation windows, Omega(calcite), and oxygen flux emphasize the importance of near-surface geochemical conditions relating to organic carbon decomposition in determining the degree and type of carbonate degradation occuring at SSETI sites.
引用
收藏
页码:571 / 584
页数:14
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