--> Abstract: Paleosols in Carbonate Successions, by V. Paul Wright; #90039 (2005)

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Paleosols in Carbonate Successions

V. Paul Wright
Cardiff University, Cardiff, United Kingdom

As most carbonate deposition takes place in shallow waters, sea level oscillations result in numerous exposure surfaces in carbonate successions. Thus sequence and parasequence boundaries are commonly marked by paleosols and many criteria are available to identify such surfaces, often associated with porosity. The range of paleosol types at carbonate exposure surfaces is small and our understanding of ancient forms has been hampered by a lack of study of modern forms. Paleosols have been used to identify topographic gradients in siliciclastic successions (catenas), and spatial variations in deposition rate have been identified by assessing paleosol “maturity” (pedofacies concept). In carbonate successions these types of relationships have not been commonly identified but instead attempts have been made to relate stages of development seen in stacked parasequence boundaries to variations in lengths of exposure, and hence to accommodation space creation. As porosity development can be linked to the lengths of exposure in such stacked successions, there is an imperative to understand how such porosity-paleosol relationships develop. There are many problems with such approaches and identifying stages of development of such paleosols can be difficult as many criteria are not time dependent. In the subsurface there are particular problems because the preservation of exposure features can be extremely spatially variable. Furthermore some exposure features can appear at different stratigraphic levels related, suggesting several exposure events, but relate to only a single exposure surface.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005