Influence of Deposition and Early Diagenesis on Porosity and Chemical Compaction in Two Paleozoic Buildups: Mississippian and Permian Age Rocks in the Sacramento Mountains, New Mexico
Eugene A. Shinn, Daniel M. Robbin, Barbara H. Lidz, J. Harold Hudson, 1983. "Influence of Deposition and Early Diagenesis on Porosity and Chemical Compaction in Two Paleozoic Buildups: Mississippian and Permian Age Rocks in the Sacramento Mountains, New Mexico", Carbonate Buildups-A Core Workshop, Paul M. Harris
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Two Paleozoic “bioherms” exposed on the western flank of the Sacramento Mountains, Otero County, New Mexico, were cored using a geologist-operated hydraulic coring device. A 16.4 m (54 ft) core penetrated the entire Scorpion Mound (14 m; 46 ft) and an underlying sandstone, both of the Laborcita Formation (Permian, Wolfcampian), whereas a 20.8 m (68 ft) core partially penetrated the central mound facies of the more than 100 m (328 ft) thick Muleshoe Mound (Mississippian, Osagean/Visean) of the Lake Valley Formation.
Preliminary study of these cores revealed: (I) Partial marine cementation of the complex “collapse-brecciated” algal plate-lime mudstone and wackestone of Scorpion Mound versus the more-thoroughly marine-cemented bryozoan and crinoidal Muleshoe Mound showed how later compaction was controlled by syn-depositional processes. For example, Muleshoe Mound, which had experienced greater overburden, contained fewer stylolites than Scorpion Mound. (2) “Collapse-breccia” is interpreted to have formed in the marine environment by compaction of an irregularly cemented void-filled lime mudstone, rather than within the vadose zone as traditionally interpreted. (3) Much of the muddy sediment and submarine botryoidal fan druse cement in Scorpion Mound formed in syndepositional cavities. The stages of internal sediment, called “vadose silt” by most workers, is interpreted as marine or early burial in origin. (4) Mounds in the Laborcita Formation were probably localized on underlying sandstone thicks. (5) Marine cementation occluded depositional porosity of the central mound facies in Muleshoe Mound, whereas most cement in the flanking crinoidal beds is of secondary origin and was probably derived as a byproduct of extensive chemical “grain-to-grain” compaction.
An appreciation of the influence of the two differing styles of syndepositional diagenesis has direct application for predicting porosity and permeability in subsurface analog buildups.
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Carbonate buildups have long been a focus of intense geological study. An underlying reason is the importance of carbonate buildups as significant hydrocarbon reservoirs. This core workshop is intended to provide a “hands on” look at the subsurface geologic record created by carbonate buildups with emphasis on lithofacies, stratigraphy of buildups and their surrounding deposits, geometry, “reef”-building and sediment-producing organisms, and diagenesis and porosity evolution