The Pennsylvanian system in the Sacramento Mountains, New Mexico, USA stratigraphy, petrography, depositional systems, paleontology, biostratigraphy, and geologic history
"Pennsylvanian sedimentary rocks in the Sacramento Mountains of Otero County, New Mexico, USA, are a stratigraphic section ~1 km thick that is assigned to the (ascending order) Gobbler, Gray Mesa, Beeman, Holder and Bursum (part) formations. We document an extensive flora from the Beeman Format...
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| Sprache: | eng |
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Washington, D.C.
Smithsonian Scholarly Press
2021
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| Schriftenreihe: | Smithsonian contributions to paleobiology
number 104 |
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Tag hinzufügen | Zusammenfassung: | "Pennsylvanian sedimentary rocks in the Sacramento Mountains of Otero County, New Mexico, USA, are a stratigraphic section ~1 km thick that is assigned to the (ascending order) Gobbler, Gray Mesa, Beeman, Holder and Bursum (part) formations. We document an extensive flora from the Beeman Formation in the northern Sacramento Mountains. Limited arthropod feeding on this flora is also documented, as are some animal fossils from the Beeman Formation. Fossil plant remains from the study area are concentrated in the Beeman Formation, with small collections from the uppermost Gobbler and lowermost Holder formations. All of the Beeman Formation collections are of Late Pennsylvanian, Missourian age. The flora is of a "mixed" composition, meaning it contains typical Pennsylvanian wetland elements, but also includes taxa considered to be indicative of habitats with seasonal soil-moisture deficits. All floral collections are allochthonous to various degrees. They are found in deposits indicative of coastal, perimarine/brackish water depositional environments, containing a variety of invertebrate remains reflective of fresh to somewhat saline conditions. Most of the Beeman Formation plant collections are dominated by drought-tolerant taxa, based on quantitative analyses of mass collections. The drought-tolerant elements include coniferophytes, callipterids, taeniopterids, noeggerathialeans, Sphenopteris germanica, and other, rare forms. Typical wetland elements include such taxa as Sigillaria brardii, Neuropteris ovata, Macroneuropteris scheuchzeri, marattialean fern foliage, various kinds of calamitalean stem and foliar remains, and small ferns. There also are various pteridosperm taxa considered to be intermediate in their moisture-stress. The plants present in these collections are indicative of a background climate that was seasonally wet-dry at the time the floras occupied the local area. It is very unlikely that drought-tolerant plants came exclusively from "uplands," although there were uplands relatively close to the fossil-flora depositional environments. The Beeman Formation floras are consistent with an early Late Pennsylvanian age. They do, however, contain a few elements more characteristic of later time intervals. Previous analyses have identified glacio-eustasy of the late Paleozoic ice ages as the primary driver of deposition throughout the Pennsylvanian section in the Sacramento Mountains. However, we question this, not only because of problems with those analyses, but because of ample evidence that local tectonics and microclimate changes also had significant effects on Pennsylvanian sedimentation in this area. Three tectonic pulses of the Ancestral Rocky Mountain (ARM) orogeny can be identified in the Pennsylvanian strata in the northern Sacramento Mountains. The first tectonic pulse occurred during the Morrowan-Atokan, and, in the Sacramento Mountains is documented by an unconformity between the Gobbler Formation and underlying Mississippian strata such as the Lake Valley Formation. The Gobbler Formation represents the dominantly siliciclastic fill of the Alamo trough that formed as a northwest-southeast-trending, asymmetric intrashelf graben on the Sacramento shelf. The second tectonic pulse of the ARM orogeny is represented by the dominantly siliciclastic nonmarine, deltaic and marginal marine deposits of the Missourian Horse Ridge Member of the Beeman Formation. Finally, the Laborcita Member of the Bursum Formation documents the third tectonic pulse that occurred across the Virgilian-Wolfcampian boundary and is composed of nonmarine and marine siliciclastic sediments and shallow marine limestones, including prominent algal mounds"-- "Here, we present new and extensive data on the Pennsylvanian strata in the Sacramento Mountains [...]. Our goals here are to present new data on and to review and revise the Pennsylvanian lithostratigraphy in this area, to present new petrographic and paleontological data, and to interpret the biostratigraphy, general nature of the depositional systems, and sedimentary environments and geological history of the Pennsylvanian strata." -- introduction, page 1 |
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| Beschreibung: | 215 Seiten Illustrationen, Diagramme, Karten |