Stratigraphy of the Upper Cambrian, Llano Uplift, Texas

Bridge, Josiah; Barnes, V. E.; Cloud, Préston

doi:10.1130/0016-7606(1947)58[109:sotucl]2.0.co;2

Cited by 16 publications

(18 citation statements)

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“…Numbers indicating sections containing microbial carbonate are coloured in blue, whereas those composed of siliciclastic facies are red. (D) Stratigraphic cross section of the Point Peak Member of the Wilberns Formation (modified from Bridge et al , 1947; Ahr, 1967). Location of sections is shown in (C).…”

Section: Geologic Settingmentioning

confidence: 99%

“…Previous studies of the upper Cambrian carbonates in the Llano area (central Texas) have mainly focussed on regional facies, stratigraphic mapping and biostratigraphy (Bridge et al , 1947; Sliger, 1955; Barnes and Bell, 1977; Miller et al , 2012), with only a few studies on the microbial reef structures and palaeoecology (Ahr, 1967, 1971; Ruppel and Kerans, 1987; Spincer, 1997). The authors recent research efforts have included detailed characterization of the smaller microbial mounds and biostromes of the lower Point Peak Member, the larger microbial buildups and associated sediments in the upper Point Peak Member, and detailed characterization of the facies succession of the upper Morgan Creek Member and Point Peak Member of the Wilberns Formation in the area along the Llano and James rivers, and Mill Creek south‐west of Mason, Texas (Kelleher et al , 2017; Khanna et al , 2019; Proctor et al , 2019).…”

Section: Introductionmentioning

confidence: 99%

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Controls on microbial and oolitic carbonate sedimentation and stratigraphic cyclicity within a mixed carbonate‐siliciclastic system: Upper Cambrian Wilberns Formation, Llano Uplift, Mason County, Texas, USA

Lehrmann

Droxler

Harris

et al. 2020

The Depositional Record

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The upper Cambrian Wilberns Formation in central Texas records deposition on a low-gradient shelf within a mixed carbonate-siliciclastic tidal-flat system that changes offshore to subtidal shelf and open-marine oolitic skeletal shoals with large microbial mounds. Siliciclastic sediment is interpreted to have been delivered to the tidal flat by aeolian processes because of the narrow range in grain size and paucity of clay. Tidal influence is dominant as evidenced by reversing currents and desiccation on the tidal flat, and megaripples with reversing current indicators in offshore shoals. Intraclastic conglomerates were deposited in broad channels on the tidal flats during storm surges. Microbialite deposition is interpreted to be controlled by accommodation favouring amalgamated thin biostromes developed in the tidal flat vs. larger mounds with greater synoptic relief in the offshore, and current energy resulting in preferential elongation of offshore mounds in a NE-SW orientation. Intertidal mounds and biostromes grew in the presence of significant siliciclastic flux and trapped it within their structure, whereas offshore large buildups incorporated little siliciclastic component. Oolite and skeletal grainstone formed in tide agitated shoals associated with large subtidal microbial mounds. Storms extensively recycled and redistributed skeletal and oolitic sands from the offshore shoals across the shelf as thin sand sheets. Spatial mixing of siliciclastic and carbonate sediment occurred across the tidal flat and shelf. Low-frequency and intermediate-frequency stratigraphic cycles were driven by shifts in the shoreline and changes in rate of siliciclastic flux in response to relative sea-level fluctuation. Random facies stacking and the lack of metre-scale cyclicity are interpreted to reflect stratigraphic incompleteness and an episodic signal introduced by storms.K E Y W O R D S Cambrian, carbonate, Laurentia, microbialite, oolite, siliciclastic 278 | LEHRMANN Et AL.microbialites, oolites and other deposits such as flat-pebble conglomerates, and the controls on cyclicity, in the Wilberns Formation through evaluation of the environmental constraints provided by sedimentary structures and sediment composition in detailed stratigraphic sections of a mixed carbonate-siliciclastic system.

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Section: Geologic Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Controls on microbial and oolitic carbonate sedimentation and stratigraphic cyclicity within a mixed carbonate‐siliciclastic system: Upper Cambrian Wilberns Formation, Llano Uplift, Mason County, Texas, USA

Lehrmann

Droxler

Harris

et al. 2020

The Depositional Record

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“…These sections are part of the Threadgill Creek section measured and described by V.E. Barnes (Bridge et al, 1947) and later expanded by Barnes and Bell (1977). The faunas of these strata have been the subject of numerous investigations particularly focusing on trilobite and conodont biostratigraphy (Bell and Ellinwood, 1962; Winston and Nicholls, 1967; Longacre, 1970; Miller et al, 1982; Stitt and Miller, 1987; Miller and Stitt, 1995; Stitt and Metcalf, 1995; Miller et al, 2003, 2012; Loch and Taylor, 2011).…”

Section: Field Area and Methodsmentioning

confidence: 99%

Linguliform brachiopods across a Cambrian–Ordovician (Furongian, Early Ordovician) biomere boundary: the Sunwaptan–Skullrockian North American Stage boundary in the Wilberns and Tanyard formations of central Texas

Freeman¹,

Miller²,

Dattilo³

2018

J. Paleontol.

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The Cambrian-Ordovician Diversity Plateau, between the Cambrian Explosion and the Ordovician Radiation, is punctuated by a series of well-documented Laurentian trilobite extinction events. These events define the bounding surfaces of trilobite ‘biomeres’ that correspond to North American stages, including those of the Sunwaptan and Skullrockian. Trilobites show a consistent pattern of recovery across these boundaries, and commonly each extinction and replacement of taxa is interpreted as a single event as changing environmental conditions spurred shoreward migration of shelf or oceanic faunas that displaced established cratonic faunas. Linguliform brachiopods are also abundant in strata of this interval, and we investigate their stratigraphic distribution across the Sunwaptan–Skullrockian Stage boundary in Texas through high-resolution stratigraphic sampling of subtidal sediments. We document complete genus- and species-level turnover of the linguliform brachiopod fauna coincident with trilobite extinction events, suggesting that these brachiopods were affected by the same factors that affected trilobites. The Skullrockian replacement fauna was cosmopolitan, with ties to Gondwana and Kazakhstan and to the Laurentian shelf environment. The timing of appearances of taxa suggests that the faunal migration onto the Laurentian shelf came from elsewhere during a transgression. The disappearance of the Sunwaptan fauna and the arrival of the Skullrockian fauna are distinct events. We suggest that ‘biomere’ events may be complex, and the cause of the extinction is not necessarily the same event that facilitates the appearance of a replacement fauna. We describe one new species,Schizambon langei.UUID:http://zoobank.org/f6a5c11f-cd3d-4c16-b184-d808d3a5285f

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“…The strata of the upper part of the Riley, exposed in the outcrops at Backbone Ridge and North Fork of Morgan Creek, display this regressive shift in depositional environment. Previous studies which have contributed to the present analysis are: Paige (191 I , 1912), who originally mapped this region; Bridge, Barnes & Cloud (1947), who defined the Riley Formation; Bell & Barnes (1962): Dekker (1966), who recognized some tidal channels in the Lion Mountain Member; and King (1976), whose analysis of the depositional environments within the middle and upper parts of the Riley Formation were invaluable to my interpretation of the origin of the Lion Mountain Sandstone.…”

Section: Regional G E O L O G Ymentioning

confidence: 99%

A trough cross‐stratified glaucarenite: a Cambrian tidal inlet accumulation

Chafetz

1978

Sedimentology

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The upper part of the Riley Formation, Cambrian of central Texas, is primarily composed of a sequence of thoroughly trough cross‐stratified deposits. The dominant lithologies range from fossiliferous glaucarenite to highly glauconitic bio‐sparrudite. These cross‐stratified deposits accumulated within a tidal inlet and associated lagoonal tributary and distributary channels. Tidal inlet‐fill strata are underlain by shallow, open marine oosparites and biomicrites and are overlain by parallel bedded glaucarenites which accumulated as part of a barrier island complex. The parallel bedded deposits exhibit large scale, gently inclined strata, ripple cross‐stratification, and a minor amount of vertical burrows. Some glaucarenite units within the tidal inlet‐fill have local concentrations of skeletal material, primarily trilobite carapaces. These concentrations are most abundant in the bottoms of troughs. Cementation by bladed to fibrous spar between the carapaces has resulted in the nodular appearance of these skeletal accumulations. Calcite clasts, with relict evaporite textures, occur within the carbonate nodules and surrounding glaucarenite. These clasts were eroded from the shallow subsurface of the barrier island as the tidal inlet migrated. The presence of the former evaporite clasts attest to an arid climate at the time of their formation.

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Stratigraphy of the Upper Cambrian, Llano Uplift, Texas

Cited by 16 publications

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Controls on microbial and oolitic carbonate sedimentation and stratigraphic cyclicity within a mixed carbonate‐siliciclastic system: Upper Cambrian Wilberns Formation, Llano Uplift, Mason County, Texas, USA

Controls on microbial and oolitic carbonate sedimentation and stratigraphic cyclicity within a mixed carbonate‐siliciclastic system: Upper Cambrian Wilberns Formation, Llano Uplift, Mason County, Texas, USA

Linguliform brachiopods across a Cambrian–Ordovician (Furongian, Early Ordovician) biomere boundary: the Sunwaptan–Skullrockian North American Stage boundary in the Wilberns and Tanyard formations of central Texas

A trough cross‐stratified glaucarenite: a Cambrian tidal inlet accumulation

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