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Full-Text Articles in Geology
Odp Leg 146 Examines Fluid Flow In Cascadia Margin, Bernard A. Housen
Odp Leg 146 Examines Fluid Flow In Cascadia Margin, Bernard A. Housen
Geology Faculty Publications
For the better part of 2 decades, it has been known that dewatering of sediments accreted to or subducted beneath accretionary wedges is a fundamental aspect of the subduction-accretion process. Yet, evidence for fluid flow in modern accretionary wedges is largely secondary and based on the presence of geochemical and/or thermal anomalies [e.g., Vrolijk et al., 1991]; the analysis of seismic velocity as an indicator of porosity, which suggests a progressive loss of pore volume in a landward direction [e.g., Bray and Karig, 1985]; and the occurrence of secondary sediment microstructures characteristic of fluid movement [e.g., Maltman et …
Evolution Of The Naticid Gastropod Predator-Prey System: An Evaluation Of The Hypothesis Of Escalation, Patricia H. Kelley, Thor A. Hansen
Evolution Of The Naticid Gastropod Predator-Prey System: An Evaluation Of The Hypothesis Of Escalation, Patricia H. Kelley, Thor A. Hansen
Geology Faculty Publications
Previous work has suggested that escalation may have characterized the history of the naticid gastropod predator-prey system, based on apparent increases in drilling frequencies and the occurrence of antipredatory aptations among prey. We evaluate this hypothesis based on a comprehensive survey (over 40,000 specimens) of predation on molluscs from the Upper Cretaceous through lower Oligocene formations within the U.S. Gulf and Atlantic Coastal Plain. Patterns in drilling of both bivalve and gastropod prey are complex. Drilling frequencies were relatively low in the Cretaceous but increased sharply above the Cretaceous-Tertiary boundary, remaining high until the late Eocene. Following a significant decline …
Paleomagnetism And Tectonics Of The Crescent Formation, North Olympic Mountains, Washington, Andrew C. Warnock, Russ R. Burmester, David C. Engebretson
Paleomagnetism And Tectonics Of The Crescent Formation, North Olympic Mountains, Washington, Andrew C. Warnock, Russ R. Burmester, David C. Engebretson
Geology Faculty Publications
A stable prefolding magnetization has been discovered in pillow basalts of the Eocene lower Crescent Formation of the northem Olympic Mountains. The curved outcrop pattern of the Crescent Formation has been the target of several unsuccessful studies to test for oroclinal bending. The success of this study is due, in part, to the development of a small-diameter electric core drill for sampling the fractured rims of basalt pillows. Thermal demagnetization produced stable endpoints by 580°C in 12 of the 34 sites sampled (large within-site scatter was common in the remaining sites). Among the accepted sites, within-site scatter was small and …
Paleomagnetic Evidence Of Vertical Axis Block Rotations From The Mesozoic Of Northern Chile, Paul D. Riley, Myrl E. Beck Jr., Russ R. Burmester, Constantino Mpodozis, Alfredo Garcia
Paleomagnetic Evidence Of Vertical Axis Block Rotations From The Mesozoic Of Northern Chile, Paul D. Riley, Myrl E. Beck Jr., Russ R. Burmester, Constantino Mpodozis, Alfredo Garcia
Geology Faculty Publications
We present paleomagnetic results for three Mesozoic formations from northern Chile: La Ternera Formation (Upper Triassic), Quebrada Monardes Formation (Upper Jurassic); Cerrillos Formation (Upper Cretaceous). Results from the Cerrillos are divided into eastern (Cuesta El Gao (CEG)) and western (Elisa De Bordo (EBD)) localities. Most specimens from La Ternera volcanic and sedimentary rocks are magnetically stable, as shown by alternating field and thermal demagnetization. More complicated but still reliable results were obtained from Quebrada Monardes red beds. Normal and reverse polarities are present in both units; means of both populations are antiparallel at 95% confidence. The Quebrada Monardes Formation also …