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Abstract Studies of paleocommunities and trophic webs assume that multispecies assemblages consist of species that coexisted in the same habitat over the duration of time averaging. However, even species with similar durability can differ in age within a single fossil assemblage. Here, we tested whether skeletal remains of different phyla and trophic guilds, the most abundant infaunal bivalve shells and nektobenthic fish otoliths, differed in radiocarbon age in surficial sediments along a depth gradient from 10 to 40 m on the warm-temperate Israeli shelf, and we modeled their dynamics of taphonomic loss. We found that, in spite of the higher potential of fishes for out-of-habitat transport after death, differences in age structure within depths were smaller by almost an order of magnitude than differences between depths. Shell and otolith assemblages underwent depth-specific burial pathways independent of taxon identity, generating death assemblages with comparable time averaging, and supporting the assumption of temporal and spatial co-occurrence of mollusks and fishes.
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TAPHONOMIC INDICATORS OF DEAD OCEAN QUAHOG ( ARCTICA ISLANDICA ) SHELL AGE IN THE DEATH ASSEMBLAGE OF THE MID-ATLANTIC BIGHT CONTINENTAL SHELF
ABSTRACT Taphonomic indicators are often used to assess time-since-death of skeletal remains. These indicators frequently have limited accuracy, resulting in the reliance of other methodologies to age remains. Arctica islandica, commonly known as the ocean quahog, is a relatively widespread bivalve in the North Atlantic, with an extended lifespan that often exceeds two hundred years; hence, their shells are often studied to evaluate climate change over time. This report evaluates taphonomic age using 117 A. islandica shells collected from the Mid-Atlantic Bight offshore of the Delmarva Peninsula with radiocarbon dates extending from 60–4,400 cal years BP. These shells had varying degrees of taphonomic alteration produced by discoloration and degradation of periostracum. To determine if a relationship exists between taphonomic condition and time-since-death, radiocarbon ages were compared with the amount of remaining periostracum and type of discoloration. Old shells (individuals that died long ago) were discolored orange with no periostracum while younger shells (individuals that died more recently) had their original color, with some periostracum. Both the disappearance of periostracum and appearance of discoloration followed a logistic process, with 50% of shells devoid of periostracum and 50% discolored in about 1,000 years. The logistic form of long-term taphonomic processes degrading shell condition is first reported here, as are the longest time series for taphonomic processes in death assemblages within the Holocene record. This relationship can be utilized for triage when deciding what shells to age from time-averaged assemblages, permitting more efficient application of expensive methods of aging such as radiocarbon dating.
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- PAR ID:
- 10491583
- Publisher / Repository:
- SEPM Society for Sedimentary Geology
- Date Published:
- Journal Name:
- Palaios
- Volume:
- 38
- Issue:
- 7
- ISSN:
- 0883-1351
- Page Range / eLocation ID:
- 305 to 314
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.2110/palo.2022.030
