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Full-Text Articles in Earth Sciences
Spatial Variation Of Naticid Gastropod Predation In The Eocene Of North-America, Thor A. Hansen, Patricia H. Kelley
Spatial Variation Of Naticid Gastropod Predation In The Eocene Of North-America, Thor A. Hansen, Patricia H. Kelley
Geology Faculty Publications
Although, the fossil record of naticid gastropod drilling has played an important role in the controversy over predator-prey evolution, little is known about variation of drilling frequencies within single horizons or how predation patterns are influenced by environmental variables. Without an understanding of spatial variation in drilling, temporal patterns in drilling are difficult to interpret. We surveyed 27,554 specimens of molluscs from the Cook Mountain interval (upper middle Eocene) and Jackson Group (late Eocene) of the U.S. Gulf and Atlantic Coastal Plain to document spatial variation in naticid drilling frequencies. The Jackson Group assemblages from the Moodys Branch and Yazoo …
Magnetic Anisotropy Fabrics From The Cascadia Accretionary Prism, Bernard A. Housen, Takaharu Sato
Magnetic Anisotropy Fabrics From The Cascadia Accretionary Prism, Bernard A. Housen, Takaharu Sato
Geology Faculty Publications
Magnetic anisotropy fabrics were measured in 495 specimens collected from the Cascadia accretionary prism to characterize the development of mineral preferred orientation fabrics during deformation. Comparison of high-field and low-field susceptibilities was used to determine the relative contributions of the paramagnetic clay minerals and the ferrimagnetic trace minerals (magnetite, greigite, pyrrhotite) to the magnetic susceptibility fabrics. Sites 888 and 891 have anisotropy of magnetic susceptibility (AMS) fabrics that are controlled primarily by the ferrimagnetic minerals. Sites 889/890 and 892 have AMS fabrics that are controlled, to varying degrees, by both paramagnetic clays and the ferrimagnetic minerals. Rock magnetic experiments indicate …