Taphonomic degradation of molluscan remains during thirteen years on the continental shelf and slope of the northwestern Gulf of Mexico

Title:
Taphonomic degradation of molluscan remains during thirteen years on the continental shelf and slope of the northwestern Gulf of Mexico
Authors:
Powell, Eric N.; Staff, George M.; Callender, W. Russell; Ashton-Alcox, Kathryn A.; Brett, Carlton E.; Parsons-Hubbard, Karla; Walker, Sally E.; Raymond, Anne L.
Abstract:
In 1993, SSETI (Shelf and Slope Experimental Taphonomy Initiative) deployed shells of a suite of molluscan species in a variety of environments of preservation (EOPs) covering a range of depths and sediment types on the Gulf of Mexico continental shelf and upper slope, with the goal of measuring taphonomic rates over an extended period of time. SSETI retrieved shells from these EOPs after 2, 8, and 13 years. The degree of shell degradation was significantly influenced by species, elapsed time-since-deployment, and EOP. A suite of ‘physical’ taphonomic processes, such as dissolution, abrasion, discoloration, and edge alteration, increased in severity over the 13 years; fragmentation occurred in some species. Dissolution proceeded apace; however the incidence of chalkiness declined from high levels observed after a few years while the more extreme levels of dissolution, such as the development of a soft or deeply-dissolved surface, rose significantly in frequency. The incidence of original color declined, while fading of original color increased. Brown-to-red and green discoloration rose rapidly in the first eight years and then declined, leaving a faded shell surface. Between-habitat differences in degradation rate were significant for most taphonomic attributes. Between-species differences were minor in comparison. Thus, taphofacies, the product of the independent actions of a suite of taphonomic processes, originate from and provide information on environmental conditions. Species composition has a lesser inherent influence on the outcome. Not uncommonly, the rates of change in shell condition differed significantly between EOPs although the direction of change was coincident. This was particularly true of the summary indices such as maximum discoloration or the average degree of dissolution. The taphonomic process is nonlinear in time. Nonlinearity is EOP-dependent, becoming a defining attribute leading to disparate taphofacies types. Some taphonomic processes cannot proceed expeditiously without prior alteration of the shell through other taphonomic means. Some taphonomic conditions such as chalkiness can be intermediate states. The presumption that similar taphonomic characteristics between EOPs indicate similar environmental processes operating at similar rates is falsified by SSETI sites in which similar taphonomic indices at Year 13 accrued from different time-varying degradational rates during the preceding years.
Citation:
Powell, Eric N., George M. Staff, W. Russell Callender, Kathryn A. Ashton-Alcox, Carlton E. Brett, Karla M. Parsons-Hubbard, Sally E. Walker, and Anne Raymond. 2011. "Taphonomic degradation of molluscan remains during thirteen years on the continental shelf and slope of the northwestern Gulf of Mexico." Palaeogeography, Palaeoclimatology, Palaeoecology 312(3-4): 209-232.
Publisher:
Elsevier
DATE ISSUED:
2011-12
Department:
Geology
Type:
Article
PUBLISHED VERSION:
10.1016/j.palaeo.2010.12.006
Additional Links:
http://linkinghub.elsevier.com/retrieve/pii/S003101821000711X
Notes:
Special Issue: The Shelf and Slope Experimental Taphonomy Initiative (SSETI): Thirteen years of taphonomic observations on carbonate and wood in the Bahamas and Gulf of Mexico
PERMANENT LINK:
http://hdl.handle.net/11282/595727

Full metadata record

DC FieldValue Language
dc.contributor.authorPowell, Eric N.en
dc.contributor.authorStaff, George M.en
dc.contributor.authorCallender, W. Russellen
dc.contributor.authorAshton-Alcox, Kathryn A.en
dc.contributor.authorBrett, Carlton E.en
dc.contributor.authorParsons-Hubbard, Karlaen
dc.contributor.authorWalker, Sally E.en
dc.contributor.authorRaymond, Anne L.en
dc.date.accessioned2016-02-05T16:30:48Zen
dc.date.available2016-02-05T16:30:48Zen
dc.date.issued2011-12en
dc.identifier.citationPowell, Eric N., George M. Staff, W. Russell Callender, Kathryn A. Ashton-Alcox, Carlton E. Brett, Karla M. Parsons-Hubbard, Sally E. Walker, and Anne Raymond. 2011. "Taphonomic degradation of molluscan remains during thirteen years on the continental shelf and slope of the northwestern Gulf of Mexico." Palaeogeography, Palaeoclimatology, Palaeoecology 312(3-4): 209-232.en
dc.identifier.issn0031-0182en
dc.identifier.urihttp://hdl.handle.net/11282/595727en
dc.description.abstractIn 1993, SSETI (Shelf and Slope Experimental Taphonomy Initiative) deployed shells of a suite of molluscan species in a variety of environments of preservation (EOPs) covering a range of depths and sediment types on the Gulf of Mexico continental shelf and upper slope, with the goal of measuring taphonomic rates over an extended period of time. SSETI retrieved shells from these EOPs after 2, 8, and 13 years. The degree of shell degradation was significantly influenced by species, elapsed time-since-deployment, and EOP. A suite of ‘physical’ taphonomic processes, such as dissolution, abrasion, discoloration, and edge alteration, increased in severity over the 13 years; fragmentation occurred in some species. Dissolution proceeded apace; however the incidence of chalkiness declined from high levels observed after a few years while the more extreme levels of dissolution, such as the development of a soft or deeply-dissolved surface, rose significantly in frequency. The incidence of original color declined, while fading of original color increased. Brown-to-red and green discoloration rose rapidly in the first eight years and then declined, leaving a faded shell surface. Between-habitat differences in degradation rate were significant for most taphonomic attributes. Between-species differences were minor in comparison. Thus, taphofacies, the product of the independent actions of a suite of taphonomic processes, originate from and provide information on environmental conditions. Species composition has a lesser inherent influence on the outcome. Not uncommonly, the rates of change in shell condition differed significantly between EOPs although the direction of change was coincident. This was particularly true of the summary indices such as maximum discoloration or the average degree of dissolution. The taphonomic process is nonlinear in time. Nonlinearity is EOP-dependent, becoming a defining attribute leading to disparate taphofacies types. Some taphonomic processes cannot proceed expeditiously without prior alteration of the shell through other taphonomic means. Some taphonomic conditions such as chalkiness can be intermediate states. The presumption that similar taphonomic characteristics between EOPs indicate similar environmental processes operating at similar rates is falsified by SSETI sites in which similar taphonomic indices at Year 13 accrued from different time-varying degradational rates during the preceding years.en
dc.language.isoen_USen
dc.publisherElsevieren
dc.identifier.doi10.1016/j.palaeo.2010.12.006en
dc.relation.urlhttp://linkinghub.elsevier.com/retrieve/pii/S003101821000711Xen
dc.subject.departmentGeologyen_US
dc.titleTaphonomic degradation of molluscan remains during thirteen years on the continental shelf and slope of the northwestern Gulf of Mexicoen_US
dc.typeArticleen
dc.description.notesSpecial Issue: The Shelf and Slope Experimental Taphonomy Initiative (SSETI): Thirteen years of taphonomic observations on carbonate and wood in the Bahamas and Gulf of Mexicoen_US
dc.identifier.journalPalaeogeography, Palaeoclimatology, Palaeoecologyen
dc.subject.keywordTaphonomyen_US
dc.subject.keywordDiscolorationen_US
dc.subject.keywordContinental shelfen_US
dc.subject.keywordContinental slopeen_US
dc.subject.keywordPreservationen_US
dc.subject.keywordTaphofaciesen_US
dc.subject.keywordDissolutionen_US
dc.subject.keywordShell carbonateen_US
dc.subject.keywordBurialen_US
dc.subject.keywordMollusken_US
dc.subject.keywordLong-term experimenten_US
dc.identifier.volume312en_US
dc.identifier.issue3-4en_US
dc.identifier.startpage209en_US
dc.rightsArchived with thanks to Palaeogeography, Palaeoclimatology, Palaeoecologyen
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