Spatial variation in the temporal resolution of subtropical shallow-water molluscan death assemblages

Matias Do Nascimento Ritter, Fernando Erthal, Matthewa Kosnik, João Carlos Coimbra, Darrell S Kaufman

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Fossil assemblages are expected to be time-averaged as a result of biological and physical processes that mix skeletal remains. Our quantitative understanding of time-averaging derives primarily from actualistic studies, in which direct numerical dating of individual specimens is used to assess the scale and structure of age mixing in death assemblages (incipient fossil assemblages). Here we examine the age, and the time-averaging of Mactra shells (Bivalvia: Mollusca) gathered from surface mixed siliciclastic-bioclastic sands at three sites on a passive-margin subtropical shelf (the Southern Brazilian Shelf; ∼ 33°S). Sixty Mactra specimens were individually dated using amino acid racemization (AAR) calibrated using radiocarbon ages (n=15). The time-averaging and the total age variability was based on a Bayesian approach that integrates the estimation errors and uncertainties derived from the posterior distribution associated with the AAR calibration average model. The 14C-calibrated AAR ages, pooled across all three sites, are strongly right-skewed with 97% of the individual mollusk shell age estimates ranging from 0 to 6 cal kyr BP. The magnitude of time-averaging varied inversely with the water depth, from < 15 yr at the deepest site (21 m) up to 1020-1250 yr at the shallowest site (7 m). The substantial variation in the temporal resolution across nearby sites, which are located in a seemingly homogenous depositional setting, indicates the presence of notable (if cryptic) spatial heterogeneities in local sedimentation, production, and exhumation, all increasing with water depth.

Original languageEnglish (US)
Pages (from-to)572-583
Number of pages12
JournalPalaios
Volume32
Issue number9
DOIs
StatePublished - Sep 1 2017

Fingerprint

spatial variation
shallow water
death
racemization
shell (molluscs)
amino acid
water
fossil assemblage
amino acids
fossils
water depth
shell
skeletal remains
Mollusca
molluscs
age structure
passive margin
temporal variation
Bivalvia
exhumation

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Palaeontology

Cite this

Spatial variation in the temporal resolution of subtropical shallow-water molluscan death assemblages. / Ritter, Matias Do Nascimento; Erthal, Fernando; Kosnik, Matthewa; Coimbra, João Carlos; Kaufman, Darrell S.

In: Palaios, Vol. 32, No. 9, 01.09.2017, p. 572-583.

Research output: Contribution to journalArticle

Ritter, Matias Do Nascimento ; Erthal, Fernando ; Kosnik, Matthewa ; Coimbra, João Carlos ; Kaufman, Darrell S. / Spatial variation in the temporal resolution of subtropical shallow-water molluscan death assemblages. In: Palaios. 2017 ; Vol. 32, No. 9. pp. 572-583.
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