Abstract Cambrian strata in Wisconsin compose a sheet of mostly marine sandstone, with minor dolomite, deposited during the fluctuating advance of the North American epeiric sea. Sedimentary features and fossils indicate that deposition took place in both shallower, current-dominated regimes and deeper quiet-water settings swept by episodic storm surges. The sand sheet surrounds inliers of Precambrian rocks in the Baraboo area. The Baraboo inliers are remnants of an elliptical ring of islands in a subtropical shallow sea, which were gradually buried by Cambrian and Ordovician sediments. Spectacular conglomerates composed of red quartzite clasts accumulated around the islands, which were pounded repeatedly by waves that we presume to have been generated by tropical storms. Paleomagnetic evidence places Cambrian Wisconsin in the southern tropics. Boulders up to 1.5 m in diameter are well rounded whereas larger ones (up to 8 m) are not. This suggests the possibility of estimating the magnitude of the Cambrian storm waves using knowledge from modern oceanography and from wave trough experiments by coastal engineers. Such analysis suggests waves necessary to tumble quartzite boulders 1.5 m in diameter were of the order of 7–8 m high at their point of breaking. Such magnitudes are not uncommon today during storms on many modern rocky coasts.

Abstract: A well-preserved record of phosphatic sedimentation across an ancient continental ramp is contained in Upper Leonardian–Guadalupian (Upper Permian) strata of the Phosphoria and Park City Formations exposed along the flanks of the Uinta Mountains, northeastern Utah. The Uinta Mountain exposures trend approximately down depositional dip and, unlike exposures of the type Phosphoria in the Idaho–Wyoming overthrust belt, are not structurally telescoped. This study is based on 12 detailed measured sections and hundreds of samples collected and studied macroscopically and microscopically from the uppermost Grandeur Member (Park City Formation), Meade Peak Member (Phosphoria Formation), and Franson Member (Park City Formation). The uppermost Grandeur Member is characterized by local carbonate hardgrounds, which are partially reworked in a transgressive lag at the base of the Meade Peak. Strata from the Meade Peak and Franson are described in terms of five lithofacies: 1) organic-rich dolomite, which is fine-grained, laminated, and present only in distal sections of the Meade Peak; 2) granular phosphorite packstone and grainstone, which is mainly associated with the Meade Peak and consists of peloids, phosphatic shelly debris, intraclasts, molluscan steinkerns, and local phosphatic coated grains; 3) gray shale; and 4) chert, which are most common at the transition zone between the Meade Peak and Franson Members; and 5) phosphatic dolowackestone, which comprises most of the Franson and which contains calcite-filled molds after anhydrite nodules and supratidal fabrics in more shoreward sections. Stratal architecture and stacking patterns, as well as the sedimentologic character and degree of bioturbation of individual facies, suggest that the Meade Peak and Franson members together are unconformity bounded and record a single major transgressive-regressive cycle. As such, they are interpreted as a stratigraphic sequence. In addition, detailed sedimentologic relations suggest that repetitively interbedded phosphorite, gray shale, and phosphatic dolowackestone of the transition zone between the Meade Peak and Franson were deposited in response to small-scale fluctuations in sea level, likely with associated changes in climate that affected the ramp. The nature and style of phosphate accumulation were not uniform across the ramp, but varied down depositional dip. Poorly oxygenated basin–ward positions were marked by deposition of organic-rich carbonate in which phosphate is interpreted to have grown authigenically in situ . In contrast, the inner ramp was current-winnowed, well oxygenated, and was the site of phosphate condensation, as suggested by the presence of only minor amounts of interstitial mud, the ubiquity of bioturbation, and the abundance of granular phosphorite, respectively.

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Abstract Basinal sediments in the stratigraphic record can be recognized using a biofacies model based on the distribution of shelly fauna and bioturbation in modern basins. Stagnation in modern basins is produced by density stratification which insulates bottom water from atmospheric oxygen, and by sills which prevent lateral exchange at depth with oxygenated ocean water. Such basins exhibit a tripartite layering in their water columns: (1) a mixed surface layer, well-oxygenated, approximately 50 m deep, (2) a stratified layer (pycnocline) in which oxygen decreases rapidly with depth, approximately 100 m in thickness, (3) a stagnant zone in which oxygen is absent, extending from the 150 m depth down to the basin floor. The major changes in faunal composition take place within the pycnocline, as dissolved oxygen drops below 2 ml/l. Marginally oxygenated waters (dysaerobic) contain communities with lower diversity, generally smaller body sizes, a greater dominance by infauna, and fewer calcified species than communities in well-oxygenated (aerobic) conditions. A complete lack of oxygen (anaerobic) eliminates metazoan animals. Basinal water conditions are reflected by corresponding biofacies: Aerobic—shelly fauna, infaunal bioturbation Dysaerobic—shelly fauna lacking, bioturbation by infauna persists Anaerobic—shelly fauna lacking, bioturbation also lacking; sediments laminated Recognition of these biofacies in the stratigraphic record should permit the reconstruction of basin contours and hydrography; paleoslope direction and dip angle and absolute water depths should be calculable from the biofacies distribution. Cyclic alternations of normal marine and euxinic facies can be explained as repeated lateral shifts of the basinal environments into a shallow shelf. An ancient basinal deposit, the Upper Devonian Middlesex Shale of New York, was sampled laterally in order to test the model; because the shale is thought to represent a time plane, facies changes should depict ‘'instantaneous” paleoenvironments in the basin in Late Devonian time. A west-to-east trend was established from laminated unfossiliferous shale through bioturbate non-fossiliferous mudstone to bioturbate and sparsely fossiliferous mudstone, indicating a transect from anaerobic through dysaerobic to nearly aerobic conditions. Basin depth therefore increased westward; the width of outcrop of dysaerobic facies is a function of the bathymetric gradient, calculated as 1:400 (0°09') for the Middlesex basin. The eastward limit of anaerobic facies marks the ancient pycnocline base at 150 m depth, and provides a bathymetric tie-point on the basin slope. West of this point the basin floor was continuously anoxic, while to the east dysaerobic and aerobic conditions alternated. Alternations are explained by transgression of the pycnocline up onto the eastern shelf, bringing basinal environments into areas which were normally oxygenated. Repeated shifts produced the alternating euxinic and fossiliferous sediments in the Upper Devonian marine sequence. Comparative examples of euxinic facies from carbonate basins show similar patterns. The Mississippian Rancheria Formation of New Mexico and the Permian Cutoff Formation of West Texas both overstep erosion surfaces cut into fossiliferous shelf carbonates, indicating a shift of basinal conditions shelfward. From published descriptions, both the Rancheria and Cutoff are here interpreted as representing dysaerobic conditions in waters 50-150 m deep. A further example, the shelf carbonates of the Pennsylvanian Paradox Basin, differs from the present model as the euxinic rocks are associated with an evaporite basin. The euxinic carbonates (probably dysaerobic facies) may have resulted from salinity rather than oxygen fluctuations, but the concept of deep basinal water periodically invading the shelf to produce cyclicity is similar to the Middlesex Shale example. Transgressions of the pycnocline may have accompanied actual sea level shifts or have occurred because of a change in mixing depth or sill depth. The latter situation would produce euxinic conditions across a shelf without increasing water depth there. Regressions of the pycnocline would return the shelf to aerobic conditions while the majority of the basin remained anaerobic.