TY - JOUR
T1 - One fossil record, multiple time resolutions
T2 - Disparate timeaveraging of echinoids and mollusks on a Holocene carbonate platform
AU - Kowalewski, Michał
AU - Casebolt, Sahale
AU - Hua, Quan
AU - Whitacre, Katherine E.
AU - Kaufman, Darrell S.
AU - Kosnik, Matthew A.
N1 - Funding Information:
We thank the Department of Biological Science (Macquarie University) and Jon and Beverly Thompson Foundation (University of Florida) for financial support, J. Southon (University of California–Irvine) for AMS analyses, and Carlton Brett, Gwen Daley, and an anonymous reviewer for constructive comments.
Publisher Copyright:
© 2017 The Authors.
PY - 2018/1/1
Y1 - 2018/1/1
N2 - Our quantitative understanding of the temporal resolution of the fossil record is largely based on numerical dating of Holocene bivalves. However, for paleontologically important taxa with less-robust skeletons, no quantitative estimate of time-averaging exists. Here, we compare time-averaging in sympatric accumulations of the echinoid Leodia sexiesperforata and the bivalve Tucetona pectinata on a shallow carbonate platform of San Salvador Island, Bahamas. Using graphite-target and carbonate-target accelerator mass spectrometry (AMS) radiocarbon methods, we dated 30 echinoid tests and 30 mollusk valves collected from surficial sediments at a single site. All echinoid tests yielded post-bomb (taking into account radiocarbon from nuclear weapons testing) ages, and the estimated time-averaging (interquartile age range) is at most 2 yr. In contrast, sympatric mollusk valves spanned 4000 yr with an estimated time-averaging of 1830 yr. This three-orders-of-magnitude difference in the extent of time-averaging quantifies the taphonomic expectation that echinoid tests should degrade more rapidly and experience less time-averaging when compared to more durable mollusk shells. When preserved, fossil echinoids are likely to indicate a more finely resolved fossil record than skeletally robust organisms such as mollusks, and may provide a fundamentally distinct class of paleontological data, potentially adequate for investigating biological and physical processes that operate at subdecadal time scales. Immensely disparate time-averaging of sympatric mollusks and echinoids indicates that, at broader phylogenetic scales, differences in intrinsic skeletal durability may be the main determinant of the temporal resolution of fossil assemblages.
AB - Our quantitative understanding of the temporal resolution of the fossil record is largely based on numerical dating of Holocene bivalves. However, for paleontologically important taxa with less-robust skeletons, no quantitative estimate of time-averaging exists. Here, we compare time-averaging in sympatric accumulations of the echinoid Leodia sexiesperforata and the bivalve Tucetona pectinata on a shallow carbonate platform of San Salvador Island, Bahamas. Using graphite-target and carbonate-target accelerator mass spectrometry (AMS) radiocarbon methods, we dated 30 echinoid tests and 30 mollusk valves collected from surficial sediments at a single site. All echinoid tests yielded post-bomb (taking into account radiocarbon from nuclear weapons testing) ages, and the estimated time-averaging (interquartile age range) is at most 2 yr. In contrast, sympatric mollusk valves spanned 4000 yr with an estimated time-averaging of 1830 yr. This three-orders-of-magnitude difference in the extent of time-averaging quantifies the taphonomic expectation that echinoid tests should degrade more rapidly and experience less time-averaging when compared to more durable mollusk shells. When preserved, fossil echinoids are likely to indicate a more finely resolved fossil record than skeletally robust organisms such as mollusks, and may provide a fundamentally distinct class of paleontological data, potentially adequate for investigating biological and physical processes that operate at subdecadal time scales. Immensely disparate time-averaging of sympatric mollusks and echinoids indicates that, at broader phylogenetic scales, differences in intrinsic skeletal durability may be the main determinant of the temporal resolution of fossil assemblages.
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U2 - 10.1130/G39789.1
DO - 10.1130/G39789.1
M3 - Article
AN - SCOPUS:85038872434
SN - 0091-7613
VL - 46
SP - 51
EP - 54
JO - Geology
JF - Geology
IS - 1
ER -