کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4723813 1355550 2010 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
The ∼1100 Ma Sturgeon Falls paleosol revisited: Implications for Mesoproterozoic weathering environments and atmospheric CO2 levels
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
The ∼1100 Ma Sturgeon Falls paleosol revisited: Implications for Mesoproterozoic weathering environments and atmospheric CO2 levels
چکیده انگلیسی

During the active rifting stage of the ∼1100 Ma Midcontinental Rift in North America, alluvial sediments were deposited intermittently between basalt flows on the north and south shores of present day Lake Superior. At times of depositional quiescence, paleosols developed in both areas on the alluvial sediments and on the antecedent basalt. New results from the Sturgeon Falls paleosol in Michigan characterizing the weathering processes at the time of its formation indicate moderate maturity, high degrees of hydrolysis and leaching, and a low degree of salinization. Geochemical provenance indices indicate a homogeneous source for the paleosols, and in contrast to earlier work, there is little evidence for K metasomatism. As a result, atmospheric CO2 levels of 4–6× pre-industrial atmospheric levels were calculated using a mass-balance model. This result is consistent with previous calculations from nearly contemporaneous paleosols from the other side of the Keweenawan Rift and from the ∼100 Ma younger Sheigra paleosol in Scotland. The calculated CO2 values are also consistent with the calculated weathering environment proxies that indicate weak to moderate weathering at this time frame and suggest that the higher greenhouse gas loads indicated by Paleoproterozoic paleosols had dissipated by the mid-late Mesoproterozoic.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Precambrian Research - Volume 183, Issue 4, 15 December 2010, Pages 738–748
نویسندگان
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