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    Paleoecology and taphonomy of vertebrate faunas from the Anza-Borrego Desert of California

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    Author
    Cassiliano, Michael Louis
    Issue Date
    1994
    Keywords
    Earth sciences
    Advisor
    Lindsay, Everett H.
    Committee Chair
    Lindsay, Everett H.
    
    Metadata
    Show full item record
    Publisher
    The University of Arizona.
    Rights
    Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
    Abstract
    Sedimentary deposits in the Salton Trough of California record the infilling of the northern part of the Gulf of California. The final phase of deposition began about 4.0 Ma with development of the delta plain of the Colorado River and ended about 0.9/0.7 Ma after a period during which deposition was dominated by bedload streams. During the final phase of deposition, a diverse assemblage of mammals characteristic of the Blancan and Irvingtonian Mammal Ages inhabited the area. The Blancan-Irvingtonian boundary is placed in the Fish Creek-Vallecito Creek section at the lowest stratigraphic occurrence of Hammuthus at about 1.77 Ma. The Fish Creek-Vallecito Creek section contains superposed Blancan and Irvingtonian faunas separated by a newly recognized Blancan-Irvingtonian boundary in continuously deposited sediments correlated with the magnetic polarity time scale. It is proposed that the Fish Creek-Vallecito Creek section be recognized as the standard section in which to define the Blancan-Irvingtonian boundary. Taphonomic analysis indicates that skeletal elements accumulated in five major depositional environments: tidal flat, lacustrine, channel, channel "fill", and floodplain. Only the fluvial environments produced significant skeletal abundances and taxonomic diversity. Taphonomic analysis indicates that pre-transport taphonomic processes were more important than fluvial transport in modifying thanatacoenoses. Taphonomic analysis also suggests that taxonomic diversity and relative abundances of large and small mammals are reliably preserved so that assemblages can be used in realistic, but general, analyses of paleoecology and paleocommunity structure. Actualistic and cenogram methods were used to study the Fish Creek-Vallecito Creek paleocommunity. Both methods suggest a savannah-community. The cenogram analysis shows the structure of the paleocommunity based on body size distribution. The data are grouped into assemblages based on the following criteria: change in fluvial environment, change in taxonomic composition, and change in paleoclimate. Stable, discrete small- and large-sized components with homogeneous body-size distributions are separated by an unstable medium-sized component. Results are consistent regardless of how the data are grouped, suggesting confidence in the results, stability in the paleocommunity despite environmental change, and a reality to the existence of the paleocommunity.
    Type
    text
    Dissertation-Reproduction (electronic)
    Degree Name
    Ph.D.
    Degree Level
    doctoral
    Degree Program
    Geosciences
    Graduate College
    Degree Grantor
    University of Arizona
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