Early Diagenesis and Paleosol Features of Ancient Desert Sediments: Examples from the Permian Basin
Ariel Malicse, Jim Mazzullo, 1996. "Early Diagenesis and Paleosol Features of Ancient Desert Sediments: Examples from the Permian Basin", Siliciclastic Diagenesis and Fluid Flow: Concepts and Applications, Laura J. Crossey, Robert Loucks, Matthew W. Totten, Peter A Scholle
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The Queen Formation is a sequence of carbonates, evaporites and siliciclastics that was deposited across the back-reef shelves of lhe Permian Basin during the late Permian (Guadalupian) time. lts upper clastic member was deposited in desert fluvial sandflat, eolian and sabkha environments during relative sea-level lowstands. During these lowstands, some of the exposed sediments on the shelves were subjected to soil forming processes. The presence of paleosol features has been documented in some of the carbonate units; however, their presence in the equivalent siliciclastic units has been commonly overlooked.
Most pedogenetic criteria were developed using examples from humid and vegetated regions; consequently, these criteria are absent or poorly developed in the soils of ancient deserts. Petrographic, SEM and core analyses of the upper clastic member of the Queen Formation from four fields in the Northwest shelf and Central Basin platform reveal subtle soil features that are common to arid regions. These features include: deformed structures (the destruction of the primary sedimentary structures by intra-sedimentary growth and collapse of salts), cutans (the mechanical infiltration and deposition of clays on the grain surface) and subsoil lamellae (the formation of subsurface lamellae by clay illuviation independent or controlled to some degree by the inherited stratification). Soil horizons are rare but have been identified in some of the cores. Superimposed on these pedogenetic features are early diagenetic events, which include: labile grain dissolution, hematitization and precipitation of authigenic species and precipitation of major pore-filling cements.
The pedogenetic features presented in this paper are alternative criteria that can be used to recognize subtle soil features in ancient sediments. These features also indicate subaerial exposures, and therefore, important to the sequence stratigraphic reconstruction of eustatically controlled shelves.
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Siliciclastic Diagenesis and Fluid Flow: Concepts and Applications
Research in the area of siliciclastic diagenesis has historically incorporated advances in related disciplines such as petrography and petrophysics, mineralogy, geochemistry, organic geochemistry, stratigraphy and basin analysis, and more recently, fluid flow. While the collection of papers in this publication covers a broad range of topics, an underlying theme is the importance of fluid flow in diagenetic processes. The mineralogy, texture and geochemistry of authigenic minerals provide constraints for fluid flow models, while formation waters provide modern snapshots of pore fluid evolution. Separated into two sections (Part I: Concepts and Part II: Applications), conceptual and practical applications are both represented.