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Kenneth L. Verosub

Publications and source records attributed to Kenneth L. Verosub.

3 recordsLinked to original sources
USGS2000

Recognition of primary and diagenetic magnetizations to determine the magnetic polarity record and timing of deposition of the moat-fill rocks of the Oligocene Creede Caldera, Colorado

Sedimentary and volcaniclastic rocks of the Oligocene Creede Formation fill the moat of the Creede caldera, which formed at about 26.9 Ma during the eruption of the Snowshoe Mountain Tuff. Paleomagnetic and rock magnetic studies of two cores (418 and 703 m long) that penetrated the lower half of the Creede Formation, in addition to paleomagnetic and isotopic dating studies of stratigraphically bracketing volcanic units, provide information on the age and the time span of sedimentation of the caldera fill. Normal polarity magnetization are found in Snowshoe Mountain Tuff beneath the moat sediments; in detrital-magnetite-bearing graded tuffs near the bottom of the moat fill; in an ash-fall deposit about 200 m stratigraphically about the top of core 2; and in postcaldera lava flows of the Fisher Dacite that overlie the Creede Formation. Normal polarity also characterizes detrital-magnetite-bearing tuff and sandstone unites within the caldera moat rocks that did not undergo severe sulfidic alteration. The combination of initially low magnitude of remanent magnetization and the destructive effects of subsequent diagenetic sulfidization on detrital iron oxides results in a poor paleomagnetic record for the fine-grained sedimentary rocks of the Creede Formation. these fine-grained rocks have either normal or revered polarity magnetizations that are carried by magnetite and/or maghemite. Many more apparent reversals are found that can be accommodated by any geomagnetic polarity time scale over the interval spanned by the ages of the bracketing extrusive rocks. Moreover, opposite polarity magnetization are found in specimens separated by only a few centimeters, without intervening hiatuses, and by specimens in several tuff beds, each of which represents a single depositional event. These polarity changes cannot, therefore, be attributed to detrital remanent magnetization. Many polarity changes are apparently related to chemical remanent magnetizations carried by postdepositional magnetite and maghemite that formed in rocks in which most or all detrital megnetic iron oxide was destroyed. Incipient oxidation of early diagenetic pyrite may have normal polarity Snowshoe Mountain Tuff (26.89 ± 0.0 Ma, 1 δ) and on the normal polarity postcaldera Fisher lava flows (as young as 26.23 ± 0.05 Ma, 1 δ) indicate that deposition of the Creede Formation spanned about 340-660 k.y. The intermittently defined normal polarity magnetization for the caldera-fill sequence, compared with different versions of the geomagnetic polarity time scale, is consistent with the shorter time span.

Colorado↗
USGS1981

Baseline studies of the feasibility and reliability of using animal behavior as a component in the prediction of earthquakes

This project was established to determine if it were possible to advance the state of the art in earthquake prediction by learning more about claims that unusual animal behavior was an earthquake precursor. We used intensive post-earthquake interview surveys to gather objective reports both of instances of unusual animal behavior as an earthquake precursor and of instances in which animals behaved normally prior to a moderate or large earthquake. We prepared briefing volumes describing the cultural significance and interpretation of seismicity for cultures other than our own with which we were likely to have contact. This information helped us assess the impact of cultural expectations on our data set. These briefing volumes are one of the work products of our project and are included in this final report. Since our goal was to increase the ability to predict earthquakes, we avoided study of earthquakes with known foreshocks since in those cases the unusual animal behavior might have resulted simply from the foreshocks. Our data indicates that unusual animal behavior occurs a few hours to a few days before some, but not most, earthquakes that do not have known foreshocks. Our studies of earthquake folklore support the same conclusion (pp 121-144 of this report). Even when unusual animal behavior is a precursor to a particular earthquake, most individual animals behave normally. This creates a signal to noise ratio that will reduce the potential for direct use of unusual -animal behavior in earthquake prediction, but the analysis of some animals reactions might help to identify physical precursors to at least some earthquakes. Each phase of this research program has produced one or more completed work products. These products, which follow, compose our final report.

Open-File Report↗