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Sequence Stratigraphy of the Lower Pennsylvanian (Bashkirian, Morrowan) Round Valley Limestone, Split Mountain Anticline (Dinosaur National Monument) and in the Eastern Uinta Mountains, UtahDavis, Nathan Robert 16 December 2010 (has links) (PDF)
The Early Pennsylvanian (Bashkirian/Morrowan) Round Valley Limestone of northeastern Utah was deposited on the Wyoming shelf, a slowly subsiding depositional surface located between the Eagle and Oquirrh basins. The 311-foot-thick Round Valley Limestone displays a distinct cyclicity formed by stacked, meter-scale parasequences, comprised of a limited suite of open- to restricted-marine limestones with minor interbeds of siltstone and shale. Open-marine deposits are characterized by mudstone and heterozoan wackestone-packstone microfacies (MF1-4) and comprise the lower portions of parasequences. Rocks of these microfacies were deposited during maximum high-order transgression of the shelf. As sediment filled the limited accommodation, the shelf became restricted, leading to deposition of mollusk-peloid dominated wackestone microfacies (MF6). Grainstones (MF5) microfacies are volumetrically limited in the Round Valley and represent deposition on isolated sand shoals that populated the shallow shelf. The complete Round Valley section at Split Mountain in Dinosaur National Monument is comprised of 5 intermediate-order sequences and 48 higher-order parasquences. Twenty-one of the shallowing-upward cycles are bounded by exposure surfaces as indicated by the occurrence of rhizoliths, glaebules, autobreccia and alveolar structures. Four of these that also indicate a significant drop in sea level (abnormal subaerial exposure surfaces and surfaces with erosional relief) constitute candidate sequence boundaries. The high percentage of cycles capped by exposure surfaces indicates that deposition of the Round Valley took place intermittently and that the Wyoming shelf was exposed during a significant portion of the Bashkirian epoch. Intermittency of deposition is confirmed by comparing the thickness and sequence architecture of the Round Valley Limestone with coeval strata in the eastern Oquirrh basin (Bridal Veil Limestone). The Bridal Veil Limestone is four times thicker and contains 24 cycles not represented on the Wyoming shelf.
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Sequence Stratigraphy of the Bridal Veil Falls Limestone, Carboniferous, Lower Oquirrh Group, on Cascade Mountain, Utah: A standard Morrowan Cyclostratigraphy for the Oquirrh BasinShoore, David Joseph 21 March 2005 (has links) (PDF)
The Bridal Veil Falls Limestone (lowest 400 meters of the Permo-Carboniferous Oquirrh Group) is well exposed on the flanks of Cascade Mountain (Wasatch Front and adjacent mountain ranges) near Provo, Utah. Because of its excellent exposure and location in the heart of the Oquirrh depocenter, this area was selected to develop a sequence stratigraphic framework for Morrowan rocks that may be applied throughout the Oquirrh basin (NW Utah and southern Idaho) as well as the adjacent Ely and Bird Springs troughs. Eleven partial to complete sections of the Bridal Veil Falls Limestone were measured along the west and north flanks of Cascade Mountain and the south end of Mt. Timpanogos. There the limestone is comprised principally of mud-rich carbonate lithofacies punctuated by thin, and sometimes discontinuous quartzose sandstone beds. The predominance of muddy to grain-rich heterozoan limestone microfacies suggests deposition on a west-dipping low energy carbonate ramp that prograded westward throughout Morrowan time. Sandstones reflect transport of siliciclastics from the incipient Weber shelf (located to the NE) during episodes of sea-level lowstand. The Bridal Veil Falls Limestone is subdivided into 21, third and fourth order depositional sequences ranging in thickness from 3 to 60 meters, and 62 parasequences. Parasequences are commonly asymmetrical, reflecting rapid flooding followed by protracted shoaling and/or sea level drop. Selected cycles are recognized in the Lake Mountains, Thorpe Hills, and the southern Oquirrh Mountains to the west of Cascade Mountain indicating that Parasequences delineated at Cascade Mountain are regionally extensive over an area of at least 300 square kilometers.
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