Several similar models of global climate and oceanic change have been proposed since 1990 to explain lithologic, eustatic, biotic and geochemical events recorded from Silurian strata. The first, and still most prominent, of the models is that of Jeppsson, who subdivided the Silurian into a series of oceanic states separated by short-lived oceanic events, during which dramatic changes, including faunal extinctions related to drops in primary productivity, occurred. Nearly all of the detailed documentation of the models comes from the Baltic region.
Testing these models requires that additional Silurian events be examined. The team will examine a span of Silurian time that includes two major events (Mulde and Lau), a minor event (Linde) and a series of shifts between oceanic episodes for which no significant 'events' have been recorded. The data will come from sections that span 3000 km across southern Laurentia, which was located distant from Baltica during the Silurian.
The research will yield a reconstruction of the depositional, biotic, and geochemical history for an interval of approximately 5.0 my across the southern craton of Laurentia and extending into basins proximal to the Appalachian orogenic area. This will allow for evaluation of geographic trends in biological and geochemical factors related to water circulation from near the cratonic margin across an epeiric sea and into basins that were more or less well connected to the global ocean and were interacting with tectonic events. This will comprise the first analysis of regional expression of Silurian oceanic changes, and will also provide the detailed documentation required for in-depth comparison to sections associated with Baltica. A far better understanding of the nature of the stratigraphic record of climatic and oceanic change for the Silurian, and thereby also the Paleozoic, will result. Data will be reposited, including unprocessed samples for additional analyses (chitinozoan, palynomorphs, Sr-isotopes, etc.), and information made available for inclusion in a dynamic, interactive and time-calibrated network, such as the CHRONOS project.
