Wage inequality, tasks and occupations

This paper assesses the relationship between occupation attributes and changes in wage inequality finding partial support for the computerization hypothesis. While wages associated with non-routine cognitive tasks have risen; current versions of the hypothesis cannot explain the pattern of within occupation wage changes, the differential impact of various types of non-routine cognitive tasks and the declining return to tasks that complement machines. Despite significant employment shifts, occupational composition alone matters little for changes in wage inequality. Changes in wage dispersion within occupations are quantitatively just as important as wage changes between occupations for explaining wage inequality between 1980 and 2000.wage inequality, computerization, skill, tasks

Deconstructing Tectonics: Ten Animated Explorations

The configuration of continents and oceans of our tectonically active planet is ever changing. Using new, high‐resolution paleogeographic base maps, we created a set of animations that examine key elements of plate tectonics. These time‐ and space‐based paleoglobe reconstructions illustrate continental rifting, continental breakup, ocean ridges and fracture zones, hot spot tracks, arc‐backarc systems, continental collision, terrane accretion, opening‐closing of ocean basins, supercontinent formation, plate velocities, and future Earth. Each animation is supported by a narrative that offers a brief topical overview, some observations to guide a user’s exploration, and key references that formulated the main ideas and concepts that became the foundations of modern plate tectonics.Key PointsFundamentals of plate tectonics are explored with paleogeographyShort animations and supporting write‐ups illustrate key processes and properties of tectonicsPresenting plate reconstructions from Cambrian to Today, and a permissible future EarthPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163371/2/ess2650.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163371/1/ess2650_am.pd

Preliminary plate tectonic reconstruction of the Indian Ocean at Anomaly M10, 34, 28, 13, and 5 times, Part I.

Contact [email protected] for more information.During the winter of 1984 work was begun on the Paleoceano­ graphic Mapping Project at the Institute for Geophysics, Univer­ sity of Texas, Austin, Texas. The goal of the Paleoceanographic Mapping Project (POMP) is to produce a set of maps and film animations illustrating the tectonic evolution of the ocean ba­ sins during the last 200 million years. The basis of these global reconstructions is a new digital data base of linear magnetic anomaly data and sea floor bathymetry. Initial support for the Paleoceanographic Mapping Project was received from British Petroleum, and as a result of their support a set of the Indian Ocean reconstructions were produced using a preliminary version of the POMP database. The six reconstructions described in this report represent the initial test of POMP data gathering procedures and mapping programs. The maps in this report are based on the published rotation parameters of Norton and Sclater (1979), Sclater et al. (1981 ), Scotese and Ross (1982), Fisher and Sclater (1983) (see Appendix I)., and represent our current understanding of the plate tectonic evolution of the Indian Ocean. These maps highlight the remaining problem areas, and serve as the starting point from which a revised set of Indian Ocean reconstructions will be produced.Paleoceanograhic Mapping Project Consortium, Institute for Geophysics, The University of Texas at AustinInstitute for Geophysic

Environmentally driven extinction and opportunistic origination explain fern diversification patterns.

Combining palaeontological and neontological data offers a unique opportunity to investigate the relative roles of biotic and abiotic controls of species diversification, and the importance of origination versus extinction in driving evolutionary dynamics. Ferns comprise a major terrestrial plant radiation with an extensive evolutionary history providing a wealth of modern and fossil data for modelling environmental drivers of diversification. Here we develop a novel Bayesian model to simultaneously estimate correlations between diversification dynamics and multiple environmental trajectories. We estimate the impact of different factors on fern diversification over the past 400 million years by analysing a comprehensive dataset of fossil occurrences and complement these findings by analysing a large molecular phylogeny. We show that origination and extinction rates are governed by fundamentally different processes: originations depend on within-group diversity but are largely unaffected by environmental changes, whereas extinctions are strongly affected by external factors such as climate and geology. Our results indicate that the prime driver of fern diversity dynamics is environmentally driven extinction, with origination being an opportunistic response to diminishing ecospace occupancy

Climate model boundary conditions for four Cretaceous time slices

International audienceGeneral circulation models (GCMs) are useful tools for investigating the characteristics and dynamics of past climates. Understanding of past climates contributes significantly to our overall understanding of Earth's climate system. One of the most time consuming, and often daunting, tasks facing the paleoclimate modeler, particularly those without a geological background, is the production of surface boundary conditions for past time periods. These boundary conditions consist of, at a minimum, continental configurations derived from plate tectonic modeling, topography, bathymetry, and a vegetation distribution. Typically, each researcher develops a unique set of boundary conditions for use in their simulations. Thus, unlike simulations of modern climate, basic assumptions in paleo surface boundary conditions can vary from researcher to researcher. This makes comparisons between results from multiple researchers difficult and, thus, hinders the integration of studies across the broader community. Unless special changes to surface conditions are warranted, researcher dependent boundary conditions are not the most efficient way to proceed in paleoclimate investigations. Here we present surface boundary conditions (land-sea distribution, paleotopography, paleobathymetry, and paleovegetation distribution) for four Cretaceous time slices (120 Ma, 110 Ma, 90 Ma, and 70 Ma). These boundary conditions are modified from base datasets to be appropriate for incorporation into numerical studies of Earth's climate and are available in NetCDF format upon request from the lead author. The land-sea distribution, bathymetry, and topography are based on the 1°×1° (latitude × longitude) paleo Digital Elevation Models (paleoDEMs) of Christopher Scotese. Those paleoDEMs were adjusted using the paleogeographical reconstructions of Ronald Blakey (Northern Arizona University) and published literature and were then modified for use in GCMs. The paleovegetation distribution is based on published data and reconstructions and consultation with members of the paleobotanical community and is represented as generalized biomes that should be easily translatable to many vegetation-modeling schemes

Kimmeridgian-Tithonian sea-level fluctuations in the Uljanovsk-Saratov Basin (Russian Platform)

Abstract The Uljanovsk-Saratov Basin, located in the southeast of the Russian Platform, presents an intriguing record of the Kimmeridgian-Tithonian sea-level fluctuations. In the Late Jurassic, this basin was a trough within the Interior Russian Sea. The data available from both outcrops and boreholes have permitted outlining a number of lithostratigraphic units and regional hiatuses in the northeastern segment of the Uljanovsk-Saratov Basin, thus permitting a precise reconstruction of transgressions/regressions and deepenings/shallowings. In total, three transgressive-regressive cycles and two deepening pulses have been established. These regionally documented changes were both related in part to global eustatic changes, and they also corresponded in part to the regional sea-level changes in some basins of Western Europe and Northern Africa, but not to those of the Arabian Platform. Differences observed between the global and regional curves as well as rapid Tithonian sea-level oscillations are explained by the influences of tectonic activity. It is hypothesized that the regional Tithonian oxygen depletion might have been a consequence from the rapid flooding of a densely vegetated land

Elevated CO2 degassing rates prevented the return of Snowball Earth during the Phanerozoic

The Cryogenian period (~720–635 Ma) is marked by extensive Snowball Earth glaciations. These have previously been linked to CO₂ draw-down, but the severe cold climates of the Cryogenian have never been replicated during the Phanerozoic despite similar, and sometimes more dramatic changes to carbon sinks. Here we quantify the total CO₂ input rate, both by measuring the global length of subduction zones in plate tectonic reconstructions, and by sea-level inversion. Our results indicate that degassing rates were anomalously low during the Late Neoproterozoic, roughly doubled by the Early Phanerozoic, and remained comparatively high until the Cenozoic. Our carbon cycle modelling identifies the Cryogenian as a unique period during which low surface temperature was more easily achieved, and shows that the shift towards greater CO₂ input rates after the Cryogenian helped prevent severe glaciation during the Phanerozoic. Such a shift appears essential for the development of complex animal life

A horseshoe crab (Arthropoda: Chelicerata: Xiphosura) from the Lower Devonian (Lochkovian) of Yunnan, China

This is the publisher's version, also available electronically from http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8826898&fileId=S0016756812000891A single specimen of a new species of the synziphosurine Kasibelinurus Pickett, 1993 is described from the Lower Devonian (Lochkovian) Xiaxishancun Formation of Yunnan Province, China. The new species, K. yueya sp. nov., extends the geographic extent of the family Kasibelinuridae from the Australian palaeocontinent to the South China palaeocontinent, and the stratigraphic range back some 50 Ma from Late to Early Devonian

The fate of the homoctenids (Tentaculitoidea) during the Frasnian-Famennian mass extinction (Late Devonian)

The homoctenids (Tentaculitoidea) are small, conical-shelled marine animals which are amongst the most abundant and widespread of all Late Devonian fossils. They were a principal casualty of the Frasnian-Famennian (F-F, Late Devonian) mass extinction, and thus provide an insight into the extinction dynamics. Despite their abundance during the Late Devonian, they have been largely neglected by extinction studies. A number of Frasnian-Famennian boundary sections have been studied, in Poland, Germany, France, and the United States. These sections have yielded homoctenids, which allow precise recognition of the timing of the mass extinction. It is clear that the homoctenids almost disappear from the fossil record during the latest Frasnian “Upper Kellwasser Event”. The coincident extinction of this pelagic group, and the widespread development of intense marine anoxia within the water column, provides a causal link between anoxia and the F-F extinction. Most notable is the sudden demise of a group, which had been present in rock-forming densities, during this anoxic event. One new species, belonging to Homoctenus is described, but is not formally named here