Atmospheric dust archives and drives climate change. Dust preserved in marine and continental sediments and ice has shed light on recent climate change, and dust also impacts climate via direct and indirect effects on the amount of solar energy received at Earth's surface, and by fertilization that stimulates primary productivity and thus the carbon cycle. However, the character and magnitude of the aerosol effect remains a poorly constrained variable in climate models, thus limiting the predictive capability of these models. In this research, PIs propose to assess the 'dust effect' by investigating the geologic record of a particularly dusty interval on Earth. The late Paleozoic world, 300 million years ago, was remarkably dusty, with dust flux varying on both million-year and millennial scales. This time period is also attractive as the last time that Earth's climate was analogous to today's, with large polar ice sheets. Here, PIs propose to test the overarching hypothesis that the abundant dust played a significant role in driving changes in late Paleozoic climate and linked (e.g. biotic) systems, through direct, indirect, and feedback effects. They will investigate how dust flux, atmospheric circulation, and dust transport varied between glacials and interglacials, how dust forced changes in tropical climate, and how the biosphere responded to such high atmospheric dustiness. To address these questions, PIs are targeting two time slices in localities spanning the girth of the tropics. They will examine dust distribution, assess atmospheric dustiness and wind strength and direction, and use geochemistry to examine effects on marine life. They will correlate among localities using fossils and radioisotopic dating. PIs will use the data they collect as input for climate- and dust-modeling experiments, to assess the direct and indirect effects of dust on atmospheric behavior and undertake biogeochemical modeling aimed at assessing the impact of variable nutrient fluxes on cycling of carbon. Intellectual Merit-- Results of this research will provide a high-resolution reconstruction of climate for the tropics and reveal the effects of dust on climate and life in a world characterized by variable dust flux on various timescales, within a 'glacial' world like today's. Owing to the known importance but remaining uncertainty of the roles of dust and associated aerosols in the climate system, our data will have predictive utility in expanding our understanding of Earth-system behavior across geologic time, and will provide important constraints useful for improving climate modeling. Broader Impacts--This project will involve heavy student participation (graduate and undergraduate levels), cross-disciplinary training among geologists, geochemists, and climate modelers, both in the field and laboratory. Undergraduates (geology and education majors) and minority middle-schoolers will take part through mentoring programs. Data will be archived and shared using newly developed web-accessible tools. Finally, we will use results of this research to guide the development of a traveling exhibit on the 'Paleozoic Dust Bowl' in conjunction with the Oklahoma Museum of Natural History and incorporate results in an outreach course taught (by co-PIs) at the Museum.
The mid-latitudes in the modern world are areas where climatic fluctuations and velocity of climate change are most significant. Consequently, the most significant variations inforaminiferal diversity occur at higher latitudes as already noted for the Middle Permian (Guadalupian) foraminifers’ record. The fusulinids as a large, warmwater foraminifera were quite sensitive to water temperature. The optimal watertemperature for recent warm-water benthic foraminifera with living symbionts, and consequently for fusulinids, is 20–30°C, while the lower limit is 14–16°C.The climatically-determined assemblages were distinguished in the Pennsyllvanian and Permian and described in terms of taxonomic variablity. The proposed model of climate fluctuations and paleogeography is based on analyses of temporal and spatial distribution of fusulinids in several regions (Neo-Tethys, N. America). The North American shelves during Pennsylvanian and Permian time – thoughgeographically within the tropical belt – are characterized by temperate environments with significantly lower foraminiferadiversification and rare occurrences of warm water Tethyan forms, that are in general appear in theregion as a migration entities. Such environments allow documentation of warming episodes associated withsudden immigration of warmwater and exotic forms of SWWBF that evolved elsewhere into the area. First occurrencedatum (FOD) of the forms exotic to North America duringwarming episodes are always delayed in respect oftheir First Appearance Datum (FAD) elsewhere. The time of delay and taxonomic diversity of fusulinids in NorthAmerica shelves depended on the scale and intensity of the warming episodes. Cooling events, on the otherhand, are associated with decreased taxonomic diversity and appearances of endemic forms characteristic only oftemperate water provinces. The occurrence of these forms in Boreal and North American provinces appears to beisochronous, as their environments are uniform and induce their uniform and isochronous distribution. Severalwarming and cooling episodes during Pennsylvanian–Permian time are recognized. The differences betweentaxonomic variations in each event could potentially be used for provisional estimation of the degree of climaticchange. A strong link between biotic and climatic events in North American province and the similarity of bioticchanges in the North American and other provinces suggests that paleoclimatic events in North American provincewere controlled by global factors.
