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You searched for +publisher:"University of North Carolina – Wilmington" +contributor:("Tricia Kelley"). One record found.

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1. Shroat-Lewis, Renandeacute. Taphonomy of a Pliocene ophiuroid mass mortality lagerstätte in the Tirabuzón Formation, Baja California sur.

Degree: 2009, University of North Carolina – Wilmington

Preservation of fully articulated ophiuroids (ophiuroid Lagerstätte) is rare due to rapid disarticulation of their endoskeletons. Recently, material from a mass mortality bed(s) of well preserved ophiuroids was found in the Pliocene Tirabuzón Formation, 4 kilometers north of Santa Rosalía, Baja California Sur. Unconsolidated sediment samples from the Tirabuzón Formation indicate a high abundance, yet low diversity, benthic foraminiferal assemblage. Three species are most abundant: (1) Virgulina californensis; (2) Bolivina interjuncta; and (3) Uvigerina attenuata. The high frequency of Bolivina interjuncta and Uvigerina attenuata throughout the formation suggests the Tirabuzón Formation was deposited in 200-500m water depth. The ophiuroid fossil assemblage appears to be monotaxic and was identified as the genus Ophiocnemis. Few of the ophiuroids in these samples were found whole. Instead, an anomalous (152:1) ratio of arms to discs exists. The individual arms and discs display a high degree of articulation, i.e. arms with spines still attached and articulated jaw structures. The high degree of articulation found in the arms suggests: (1) rapid burial; (2) no decomposition prior to interment; and (3) lack of post mortem reworking and bioturbation. To determine the possible cause of the abnormal ratio of arms to discs, live ophiuroids were subjected to simulated wave current coupled with turbidity, temperature, and/or salinity changes. Agitation in normal salinity/temperature seawater caused orientation difficulties and varied arm-curling responses. Changes in suspended sediment (0-235 mg/l) had no effect on the ophiuroids over a 180 minute period. Warm water (>30° C) caused arm rigidity and cool water (<18° C) caused substrate attachment difficulties. Both hypersaline (>52 ppt) and hyposaline (<24 ppt) water produced: (1) arm rigidity; (2) attachment difficulties; (3) lethargy; and/or (4) death. Arm flexibility of live ophiuroids subjected to hypersaline water was restored post mortem, but live ophiuroids exposed to hyposaline water exhibited prolonged arm rigidity. Prolonged arm rigidity, high energy storm waves, and sorting of the elongate arms from the flat central discs may account for the abnormally high arm to disc ratio in the Tirabuzón samples.; Fossils – California – Baja, Geology – California – Baja, Paleontology – California – Baja Advisors/Committee Members: Tricia Kelley (advisor).

Subjects/Keywords: Geology  – California  – Baja; Fossils  – California  – Baja; Paleontology  – California  – Baja

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APA (6th Edition):

Shroat-Lewis, R. (2009). Taphonomy of a Pliocene ophiuroid mass mortality lagerstätte in the Tirabuzón Formation, Baja California sur. (Masters Thesis). University of North Carolina – Wilmington. Retrieved from http://libres.uncg.edu/ir/listing.aspx?styp=ti&id=1791

Chicago Manual of Style (16th Edition):

Shroat-Lewis, Renandeacute. “Taphonomy of a Pliocene ophiuroid mass mortality lagerstätte in the Tirabuzón Formation, Baja California sur.” 2009. Masters Thesis, University of North Carolina – Wilmington. Accessed August 15, 2018. http://libres.uncg.edu/ir/listing.aspx?styp=ti&id=1791.

MLA Handbook (7th Edition):

Shroat-Lewis, Renandeacute. “Taphonomy of a Pliocene ophiuroid mass mortality lagerstätte in the Tirabuzón Formation, Baja California sur.” 2009. Web. 15 Aug 2018.

Vancouver:

Shroat-Lewis R. Taphonomy of a Pliocene ophiuroid mass mortality lagerstätte in the Tirabuzón Formation, Baja California sur. [Internet] [Masters thesis]. University of North Carolina – Wilmington; 2009. [cited 2018 Aug 15]. Available from: http://libres.uncg.edu/ir/listing.aspx?styp=ti&id=1791.

Council of Science Editors:

Shroat-Lewis R. Taphonomy of a Pliocene ophiuroid mass mortality lagerstätte in the Tirabuzón Formation, Baja California sur. [Masters Thesis]. University of North Carolina – Wilmington; 2009. Available from: http://libres.uncg.edu/ir/listing.aspx?styp=ti&id=1791

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