Podcasts about late quaternary

James Biemiller, USGS An unresolved aspect of tsunami generation in great subduction earthquakes is the offshore competition between coseismic deformation mechanisms, such as shallow megathrust slip, slip on one or more splay faults, and off-fault plastic deformation. In this presentation, we first review results from data-constrained 3D dynamic rupture modeling of an active plate-boundary-scale low-angle normal fault, the Mai’iu fault, that show how stress, fault structure, and the strength and thickness of overlying sediments influence shallow coseismic deformation partitioning in an extensional setting. Similar modeling approaches can shed light on shallow coseismic deformation in contractional settings, such as the Cascadia subduction zone (CSZ). Along the northwestern margin of the U.S., robust paleoseismic proxies record multiple M>8 paleoearthquakes over the Holocene, despite limited modern interface seismicity. Additionally, growth strata in the outer wedge record Late Quaternary slip on active landward- and seaward-vergent splay faults inboard of prominent variably-vergent frontal thrusts at the deformation front. The relative importance of megathrust vs. splay fault slip in generating tsunami hazards along the Pacific Northwest coastline is relatively unconstrained. Here, we develop data-driven 3D dynamic rupture models of the CSZ to analyze structural controls on shallow rupture processes including slip partitioning across the frontal thrusts, splays, and underlying decollement. Initial simulations show that trench-approaching ruptures typically involve meter-scale slip on variably oriented preexisting planar splay faults. Splay slip reduces slip on the subduction interface in a shadowed zone updip of their intersection, with greater splay slip leading to stronger shadowing. We discuss two structural controls on splay faults’ coseismic slip tendency: their dip angle and vergence. Gently dipping splays host more slip than steeply dipping ones and seaward-vergent splays host more slip than landward-vergent ones. We attribute these effects to distinct static and dynamic mechanisms, respectively. Finally, we show initial results from simulations with newly mapped frontal thrust geometries from CASIE21 seismic reflection data and discuss future directions for our CSZ dynamic rupture modeling project.

This is an interview with Steve Goodbred from Vanderbilt University about his 2000 paper; Goodbred Jr, S. L. and S. A. Kuehl (2000). "The significance of large sediment supply, active tectonism, and eustasy on margin sequence development: Late Quaternary stratigraphy and evolution of the Ganges-Brahmaputra delta." Sedimentary Geology 133(3-4): 227-248.

In this episode, we eventually get to discussing patterns of extinction selectivity in mammals during two major extinctions (the end Cretaceous and the modern biodiversity crisis). Also, James discusses delicious ways to end the world, Curt details the Lord of the Footballs, and Amanda really would like to know WHEN we're going to start discussing the papers. References: Longrich, N. R., J. Scriberas, and M. A. Wills. "Severe extinction and rapid recovery of mammals across the Cretaceous‐Paleogene boundary, and the effects of rarity on patterns of extinction and recovery." Journal of evolutionary biology (2016). Lyons, S. Kathleen, et al. "The changing role of mammal life histories in Late Quaternary extinction vulnerability on continents and islands." Biology Letters 12.6 (2016): 20160342.

In this episode, the gang is all back in the same zip code and celebrate by having a long discussion on the origin and extinction of the large mammals from the Cenozoic known as the Megafauna. Somehow this gets.... weird. Meanwhile, James defends the Star Wars Empire, Curt argues why turtles should be ninjas instead of mere heroes, and Amanda confuses Michael Bay with Roland Emmerich. Also, congrats to Dr. Amanda Falk for defending her thesis.    References: Anthony D. Barnosky et al. Assessing the Causes of Late Pleistocene Extinctions on the Continents Science 306, 70 (2004); Tao Deng et al. Out of Tibet: Pliocene Woolly Rhino Suggests High-Plateau Origin of Ice Age Megaherbivores Science 333, 1285 (2011);  Prescott, Graham W., et al. "Quantitative global analysis of the role of climate and people in explaining late Quaternary megafaunal extinctions." Proceedings of the National Academy of Sciences 109.12 (2012): 4527-4531. Lorenzen, Eline D., et al. "Species-specific responses of Late Quaternary megafauna to climate and humans." Nature 479.7373 (2011): 359-364.

Hello again. Like I said before, I’m Mark Valentine and I’m going to be talking about Megafaunal Extinction and how it affects present and future biodiversity. Before I begin, you probably are going to want to know what exactly Megafauna are. Megafauna are HUGE animals. This would certainly include animals like elephants and giraffes, but also lions, tigers and bears. All these animals, however, are relatively well known and still exist in the world today. What many people don’t know is that there were many incredible Megafauna that existed a few thousand years ago that are now extinct. Around 50,000 years ago, at the end of the last Ice Age, Megafauna worldwide underwent massive and widespread extinctions . Before then, there were all kinds of amazing and enormous animals worldwide: In Eurasia, there were wooly mammoths and saber tooth cats, which you’ve probably heard of, but in North America there were beavers the size of small cars and 9 foot tall Bison with horns that spanned over 6 feet , in South America there were 5 foot tall armadillos and Giant Ground Sloths the size of elephants , and in Australia there were wombats the size of Hippopotamuses . All these animals have two things in common: One, that they are absolutely massive, and two, that they have all contributed to the historical phenomenon that Megafauna are more likely to go extinct than smaller animals . So what caused these extinctions? There are two causes. We know that human hunting lead to the extinction of many Megafaunal species, like Steller’s Sea Cow, which was basically a 30 feet long , 20,000 pound manatee . Another major cause of these extinctions was climate change. A recent study showed that climate change had significant effect on many species, and actually may have been the cause of extinction for wooly rhinos, giant bison, and other Megafauna . So what does this mean for present and future biodiversity? It’s not good. The same two factors—humans and climate—are again playing a role in Megafaunal extinctions. As humans increase in population and expand outwards, more and more animals are being threatened, and since Megafauna need more living space than other animals they are more affected. Animals including pandas and tigers are already endangered because of this. We’re also experiencing global climate shifts due to global warming, which is already causing a decline in Megafauna like the polar bear . The continued global trend of a loss of large animals is clearly leading towards one result: a world overrun with the smallest kinds of animals which can live alongside humans, or in other words, a world overrun with rodents . But this does not have to happen. If we as humans can dramatically change the way we live to reduce climate change and preserve wildlife, we can maintain biodiversity, especially among Megafauna, for much longer. The only question is, can we change? ``` Wikipedia contributors. "Quaternary extinction event." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 20 Nov. 2011. Web. 30 Nov. 2011. Kurtén, B. and E. Anderson (1980). Pleistocene Mammals of North America. Columbia University Press. pp. 236–237. ISBN 0231037333. Wikipedia contributors. "Bison latifrons." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 13 Nov. 2011. Web. 30 Nov. 2011. Wikipedia contributors. "Doedicurus." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 16 Jun. 2011. Web. 30 Nov. 2011. Wikipedia contributors. "Megatherium." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 10 Oct. 2011. Web. 30 Nov. 2011. Wikipedia contributors. "Diprotodon." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 26 Nov. 2011. Web. 30 Nov. 2011. Turvey S. T., Fritz S. A. 2011 The ghosts of mammals past: biological and geographical patterns of global mammalian extinction across the Holocene. Phil. Trans. R. Soc. B 366, 2564–2576. Sally M. Walker (1999). Manatees. Lerner Publications. Victor B. Scheffer (November 1972). "The Weight of the Steller Sea Cow". Journal of Mammalogy 53 Hofrieter, Michael., Shapiro, Beth., et al. 2011. Species-specific responses of Late Quaternary megafauna to climate and humans. Nature 479, 359–364 (17 November 2011) Johnson, Chris. Australia's Mammal Extinctions: A 50,000 year history. 1st ed. Caimbridge: Caimbridge University Press, 2006. Print. Hunter, Christine M., Hal Caswell, Michael C. Runge, Eric V. Regehr, Steve C. Amstrup, and Ian Stirling. 2010. Climate change threatens polar bear populations: a stochastic demographic analysis. Ecology 91:2883–2897

Abi Stone, School of Geography and the Environment, Oxford, talks at the 1st Oxford Interdisciplinary Desert Conference hosted by the School of Geography and the Environment, University of Oxford, on the 15-16 April 2010.

By storing and transporting vast amounts of energy derived from solar insolation, the oceans play an important role in shaping Earth’s climate. On the largest scale, ocean currents smooth the temperature gradients between the equator and the poles by redistributing excess energy from the tropics to higher latitudes. Much of this excess heat is transported by the so-called Ocean Conveyor Belt (Broecker, 1991), a global network of ocean currents driven by thermohaline convection. Changes in the pattern and strength of thermohaline circulation affect the redistribution of heat, and thereby significantly influence climate on local to global scales. The reconstruction of paleocurrents has long been a subject of paleoceanographic research. Among the various methods employed in tracing paleocurrents (and modern currents), the Sm-Nd isotope system is experiencing ever increasing attention. First applied in an oceanographic context by O’Nions et al. (1978), it is by now established as a standard tool, as shown by numerous recent publications (e.g. Rutberg et al., 2000; Tütken et al., 2002; Weldeab et al., 2002; Benson et al., 2003; Farmer and Barber, 2003; Piotrowski et al., 2004; Bayon et al., 2002, 2003, 2004; Lacan and Jeandel, 2001, 2004, 2005, and many more). Two lines of application of the Sm-Nd isotope system to oceanography/paleoceanography can be distinguished, both of which were followed for this thesis. The first approach uses the isotopic composition of Sm and Nd hosted in detrital minerals to infer the provenance of terrigenous sediments. This information can be used to draw conclusions about the direction and distance of sediment delivery. The second approach uses the isotopic signature of Nd as a tracer of different water masses. Due to the oceanic residence time of Nd being shorter than the global turnover rate of seawater (500-1000 years vs ~1000 years; Tachikawa et al., 2003), different bodies of water acquire distinct Nd isotopic signatures as a function of the age of adjacent continents. Apart from directly analyzing the Nd isotopic compositions of water samples to trace the modern distribution of different watermasses (e.g. Lacan and Jeandel, 2001, 2004), suitable archives of seawater-derived Nd can be employed to study paleocurrents. Possible archives are fossil remains of marine organisms (e.g. foraminifers; Burton and Vance, 2000), or, most widely used for the recent geological past, Fe-Mn nodules and crusts (e.g. Frank et al., 2002). With slow growth rates on the order of mm/Ma, however, Fe-Mn nodules do not offer the high temporal resolution necessary to study Late Quaternary climate change. Attention has therefore recently turned to authigenic Fe-Mn oxyhydroxides finely dispersed throughout the sediment column (e.g. Rutberg et al., 2000; Bayon et al., 2002, 2003, 2004; Piotrowski et al., 2004). For this thesis, both lines of application of the Sm-Nd isotope system to paleoceanography were followed. The samples were taken from a sediment core collected from the Yermak Plateau in the north-eastern Fram Strait. Situated between Greenland and the Svalbard Archipelago, the Fram Strait is the only deep connection between the Arctic Ocean and, via the Greenland-Iceland-Norwegian (Nordic) Seas, the North Atlantic. The Nordic Seas are an area of deep-water formation important for the global thermohaline circulation. There, the processes of deep-water formation are in a state of equilibrium that is most sensitive to changes in surface water salinity, which, in turn, is strongly influenced by the outflow of water of low salinity from the Arctic Ocean. This makes the history of water exchange between the Atlantic and the Arctic Ocean through the Fram Strait a subject of key interest for climate research. In particular, it was attempted to reconstruct the provenance of sediments deposited on the western Yermak Plateau over the last 129 000 years. This was done by analyzing samples from the sediment core and from potential source areas for their Sm-Nd isotopic compositions. The current understanding is that under present interglacial conditions sediment is delivered to the Yermak Plateau by ice drift from the Siberian shelf areas (Kara- and Laptev Sea) and as suspended load of Atlantic water advected from the south. To resolve these assumed differences in provenance and transport mechanism, the majority of the samples was split into the grain-size fractions clay, fine silt, coarse silt, and sand for Sm-Nd analyses. The position of the investigated core on the upper slope of the western Yermak Plateau limits delivery of sand-size (or coarser) material to ice rafting. The sand fractions of the core samples were therefore interpreted to be exclusively of ice rafted origin, and thus used as an indicator of changes in the pattern of surface currents. Clay- to silt-size material, on the other hand, yields a mixed signal of ice rafting and suspended-load delivery. Based on a comparison of the isotopic compositions of the core samples with those of the samples from potential source areas, a number of conclusions can be drawn: Most core sample show only little isotopic variation between their constituent size fractions (mostly less than analytical uncertainty). Only sand fractions show considerable differences. This can probably be explained by the sand samples’ small sample size relative to their coarse grain size; as a result, most sand fractions probably are not representative. The generally good agreement between the isotopic compositions suggests a common origin of ice rafted detritus (IRD) and suspended load. The possibility of suspended particulate matter transport from the Siberian shelf areas of the Kara- and Laptev Seas to the Yermak Plateau in significant amounts can be excluded. An origin of IRD in the Kara and Laptev Sea is therefore equally unlikely. Instead, a common provenance of IRD and suspended particulate matter from the Svalbard/Barents Sea area is a plausible scenario, supported by isotope-independent data from the literature (e.g. grain-size distribution, mineralogical composition, faunal abundance, etc.). The moderate downcore Nd isotopic variation suggests that, despite repeated large-scale glaciations in the Svalbard/Barents Sea area, the general modern-type circulation in the Fram Strait area has been active for most of the last 129 000 years. The largest deviation from modern conditions is indicated for the peak of the last glacial phase, approximately 20 000 years ago. Then, large amounts of IRD were delivered to the Yermak Plateau by icebergs calving from the Scandinavian ice sheet. Moreover, the occurrence of chalk fragments confirms iceberg drift from as far south as the North Sea. A similar finding has previously been reported for samples from the southern Fram Strait by Spielhagen (1991). Regarding the second analytical approach, i.e. the Nd isotopic analysis of finely dispersed authigenic Fe-Mn oxyhydroxides, implementation of the experimental technique was targeted first. The method of Fe-Mn oxyhydroxide extraction by means of leaching with a mixed reagent (acetic acid and hydroxylamine-hydrochloride) largely is based on the work of Chester and Hughes (1967). Modifications of their method have been reported in Tessier et al. (1979), Chao and Zhou (1983), and Hall et al. (1996), and have recently been compared by Bayon et al. (2002). Based on the experimental protocol described by Bayon et al. (2002), five core samples were processed and analyzed for their rare earth element (REE) concentrations by ICP-MS at the European Union Large Scale Geochemical Facility at the University of Bristol, England, financed by the EU. In addition, nine core samples were processed and the leachates analyzed for their Nd isotopic composition in Munich. The REE patterns of the leachates show an enrichment of the middle REE that is atypical for authigenic Fe-Mn phases. The isotopic analysis also yielded controversial results: downcore, the Nd isotope curves for the leachates and the detrital phases run approximately parallel, suggesting a systematic genetic relationship between the analyzed Nd fractions. A similar relationship appears to exist between data reported in Rutberg (2000), Rutberg et al. (2000), and Piotrowski et al. (2004) for a sediment core from the south-eastern Atlantic. To answer the questions raised by these controversial results, a sequential leaching experiment was designed. Several aliquots of one core sample were treated for different durations with different concentrations of the leaching reagents, and at intermediate steps were analyzed for their Sm-Nd isotopic composition. The results of this leaching experiment point towards a conceptual weakness of the method. In order to avoid contamination by non-authigenic sediment components, all experimental methods described in the literature focus on adjusting the concentration of the hydroxylamine-hydrochloride used to reduce Fe and Mn to their soluble states. This approach, however, does not take into account the dissolution of acid-soluble phases by acetic acid, which in all cases is used at a strength of 4.4 mol·l-1. Consequently, the leaching reagent is sufficiently corrosive to attack easily-soluble detrital minerals and release non-seawater-derived Nd (Hannigan and Sholkovitz, 2001; Dubinin and Strekopytov, 2001). Phosphatic phases are therefore a likely source of nonseawater-derived Nd. Apatite, for instance, is a common component of clastic sedimentary rocks, is easily dissolved by weak acids, and can account for the middle REE enrichment in the leachates. Its high Nd concentrations would mask any seawater signal. To conclude, it appears as though the available extraction techniques are not yet sufficiently refined to reliably determine the Nd isotopic composition of finely dispersed Fe-Mn oxyhydroxides as a proxy for paleoseawater composition.

Sat, 1 Jan 1994 12:00:00 +0100 http://epub.ub.uni-muenchen.de/8444/ http://epub.ub.uni-muenchen.de/8444/1/late_quaternary_extinction_of_ungulates_in_sub-saharan_africa_8444.pdf Peters, Joris; Gautier, A.; Brink, J. S.; Haenen, W. Peters, Joris; Gautier, A.; Brink, J. S. und Haenen, W. (1994): Late quaternary extinction of ungulates in Sub-Saharan Africa. A Reductionist`s Approach. In: Journal of Archaeological Science, Vol. 21: pp. 17-28. Tiermedizin

Wed, 1 Jan 1992 12:00:00 +0100 http://epub.ub.uni-muenchen.de/8392/ http://epub.ub.uni-muenchen.de/8392/1/8392.pdf Peters, Joris Peters, Joris (1992): Late Quaternary Mammalian remains from Central and Eastern Sudan and their palaeoenvironment Significance. In: Zinderen Bakker, E. M. van und Heine, Klaus (Hrsg.), Palaeoecology of Africa and the surrounding islands. Bd. 23, Balkema: Rotterdam, pp. 91-115.