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Dominance of reworked fossil shells in modern estuarine environments; implications for paleoenvironmental reconstructions based on biological remains

Claudio G. de Francesco and Gabriela S. Hassan
Dominance of reworked fossil shells in modern estuarine environments; implications for paleoenvironmental reconstructions based on biological remains
Palaios (January 2008) 23 (1): 14-23

Abstract

Death assemblages from contemporary marginal marine settings carved into ancient shell deposits are composed of fossil shells exhumed by currents or tides and shells derived from living populations. A better understanding of the bias produced by such a mixing process is of interest for studies that use modern death assemblages as analogues of similar past habitats. In order to evaluate the magnitude of reworking and redeposition of fossil shells in modern environments, a taxonomic (composition, abundance, and richness) and taphonomic (taphofacies) study was carried out in the Mar Chiquita coastal lagoon, Argentina (37 degrees 40'S, 57 degrees 20'W). The nature and extent of reworking was explored along a gradient in tidal energy from the outer to the inner reaches of the coastal lagoon. Results indicate that modern death assemblages in the lagoon are composed mostly of fossil (late Holocene) reworked shells and that reworking varies along a gradient in tidal energy, being higher in the outer reaches of the coastal lagoon, where tidal action is more significant. Temporal mixing in the coastal lagoon appears to be associated with condensation (remanie) rather than with a subtle mixing of shells, as occurs in time-averaged deposits. This reworking process leads to an abundance of old shells in modern death assemblages, which has negative consequences for their utilization as modern analogues of past lagoons. Multidisciplinary studies involving various biological indicators need to take this type of bias into consideration in order to avoid erroneous inferences on the Quaternary evolution of coastal lagoons.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 23
Serial Issue: 1
Title: Dominance of reworked fossil shells in modern estuarine environments; implications for paleoenvironmental reconstructions based on biological remains
Affiliation: Universidad Nacional de Mar del Plata, Centro de Geologia de Costas y del Cuaternario, Mar del Plata, Argentina
Pages: 14-23
Published: 200801
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 56
Accession Number: 2008-064209
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch map
S37°40'00" - S37°40'00", W57°19'60" - W57°19'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 200815
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