{sup 210}Pb chronology of sequences affected by burrow excavation and infilling: Examples from shallow marine carbonate sediment sequences, Holocene South Florida and Caicos Platform, British West Indies

Journal Article · Wed Jan 01 04:00:00 EST 1997 · Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes

OSTI ID:452182

Tedesco, L P ^[1]; Aller, R C ^[2]

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1. Indiana/Purdue Univ., Indianapolis, IN (United States). Dept. of Geology
2. State Univ. of New York, Stony Brook, NY (United States). Marine Sciences Research Center

A variety of sedimentological criteria and direct field observations indicate that deposits of shallow carbonate platforms and mud banks are extensively transformed during megafaunal bioturbation by deep-burrowing crustaceans. {sup 210}Pb dating of surficial sediment and burrow fills dissected from the upper 1--3 m of sediments at four sites on the Caicos Platform and in South Florida corroborates sedimentologic descriptions of rapid biogenic alteration of entire facies. {sup 210}Pb distributions from the study sites show that at least some infill is predominantly surficial sediment. Assuming that all identifiable deep burrow fills containing excess {sup 210}Pb derive from the uppermost 0--5 cm interval, an estimate of facies replacement by nonlocal transport can be made based on measured excess {sup 210}Pb values of fill and the corresponding total discernible fill volume in cores. Calculations indicate that at the sites studied, burrow excavation and infilling can completely transform the upper 1--2 m, and possibly 3.5 m, of deposits in 100--600 yr. More rapid transformation of deposits is required if fill is derived from below 5 cm. Biogenic transformation rates are sufficiently fast compared to net sedimentation that burrow infills, not primarily physical deposition, determine the composition, porosity, fabric, and texture of the preserved facies. The {sup 210}Pb profiles in the deepest regions of deposits in the present cases are further complicated by basal enrichments of {sup 226}Ra, which apparently diffuses upwards from Pleistocene calcrete surfaces into overlying Holocene sediment. This diffusion requires careful documentation of supported {sup 210}Pb near this contact, but also offers the potential for an additional transport tracer internal to the deposits.

• Sponsoring Organization: National Science Foundation, Washington, DC (United States)
• OSTI ID: 452182
• Journal Information: Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes, Journal Name: Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes Journal Issue: 1 Vol. 67; ISSN JSRAEA; ISSN 1073-130X
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
58 GEOSCIENCES
BIOINTRUSION
CARBONATE ROCKS
DIAGENESIS
FLORIDA
GEOLOGIC DEPOSITS
ISOTOPE DATING
LEAD 210
WEST INDIES