Scale and structure of time-averaging (age mixing) in terrestrial gastropod assemblages from Quaternary eolian deposits of the eastern Canary Islands

Torres Pérez-Hidalgo, Trinidad José (2007). Scale and structure of time-averaging (age mixing) in terrestrial gastropod assemblages from Quaternary eolian deposits of the eastern Canary Islands. "Palaeogeography, Palaeoclimatology, Palaeoecology", v. 251 (n. 2); pp. 283-299. ISSN 0031-0182. https://doi.org/10.1016/j.palaeo.2007.04.002.

Description

Title: Scale and structure of time-averaging (age mixing) in terrestrial gastropod assemblages from Quaternary eolian deposits of the eastern Canary Islands
Author/s:
  • Torres Pérez-Hidalgo, Trinidad José
Item Type: Article
Título de Revista/Publicación: Palaeogeography, Palaeoclimatology, Palaeoecology
Date: August 2007
ISSN: 0031-0182
Volume: 251
Subjects:
Faculty: E.T.S.I. Minas (UPM)
Department: Ingeniería Geológica [hasta 2014]
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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Abstract

Quantitative estimates of time-averaging (age mixing) in gastropod shell accumulations from Quaternary (the late Pleistocene and Holocene) eolian deposits of Canary Islands were obtained by direct dating of individual gastropods obtained from exceptionally well-preserved dune and paleosol shell assemblages. A total of 203 shells of the gastropods Theba geminata and T. arinagae, representing 44 samples (= strati graphic horizons) from 14 sections, were dated using amino acid (isoleucine) epimerization ratios calibrated with 12 radiocarbon dates. Most samples reveal a substantial variation in shell age that exceeds the error that could be generated by dating imprecision, with the mean within-sample shell age range of 6670 years and the mean standard deviation of 2920 years. Even the most conservative approach (Monte Carlo simulations with a non-sequential Bonferroni correction) indicates that at least 25% of samples must have undergone substantial time-averaging (e.g., age variations within those samples cannot be explained by dating imprecision alone). Samples vary in shell age structure, including both left-skewed (17 out of 44) and right-skewed distributions (26 out of 44) as well as age distributions with a highly variable kurtosis. Dispersion and shape of age distributions of samples do not show any notable correlation with the stratigraphic age of samples, suggesting that the structure and scale of temporal mixing is time invariant. The statistically significant multi-millennial time-averaging observed here is consistent with previous studies of shell accumulations from various depositional settings and reinforces the importance of dating numerous specimens per horizon in geochrono logical studies. Unlike in the case of marine samples, typified by right-skewed age distributions (attributed to an exponential-like shell loss from older age classes), many of the samples analyzed here displayed leftskewed distributions, suggestive of different dynamics of age mixing in marine versus terrestrial shell accumulations.

More information

Item ID: 3450
DC Identifier: http://oa.upm.es/3450/
OAI Identifier: oai:oa.upm.es:3450
DOI: 10.1016/j.palaeo.2007.04.002
Official URL: http://www.elsevier.com/wps/find/journaldescription.cws_home/503355/description
Deposited by: Biblioteca ETSI Minas y Energía
Deposited on: 26 Jun 2010 06:45
Last Modified: 20 Apr 2016 12:59
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