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No description available.

A completely new Upper Cambrian formational nomenclature is proposed for the southern Rocky Mountains of Alberta. The formations designated as Upper Cambrian are: Corona, and Mount Synge, Dresbachian; Bison Creek, Franconian; and the Mistaya, Trempealeauan. Two additional formations are referred to the Middle Cambrian sequence immediately underlying the Upper Cambrian; the Chephren and the Waterfowl. These latter formations were previously included in the Arctomys formation considered to be Upper Cambrian in age. The lowest Lower Ordovician formation is designated as the Howse River formation. In addition to the above mentioned new formations, the Arctomys, Sullivan, Lyell, Mons, Bosworth, Paget, Sherbrooke, Tangle Ridge, and Sabine formations are discussed in detail. All are considered obsolete, except the Sabine formation, the use of which, it is recommended, be confined to the Canal Flats area, British Columbia. The limits of the Upper Cambrian series in Alberta are more precisely determined, and tentative correlation of the Upper Cambrian of Alberta, Montana, and British Columbia is outlined. Trilobite faunas from all the Upper Cambrian zones, except the Crepicephalus zone, are described and illustrated. The Cedaria zone faunas contain fifteen genera and eighteen species, among them Bolaspidelia wellsvillensis, Nixonella montanensis, several species of Arapahoia and Cedarina, and Kingstonia mucro. Abundant topotype material of K. mucro has made redefinition of this species possible. The Aphelaspis zone is recognized by the discovery of Aphelaspis walcotti, and one questionable species of Aphelaspis. The Franconian zones are represented by Irvingella major, Taenicephalus shumardi, Parabolinoides cordiIlerensis, Maustonia nasota, KendalIina eryon, Ptychaspis striata, Prosaukia lonqicornis and Prosaukia curvicostata, to mention only the more important index species. The Saukia zone of the Trempealeauan is represented by species of Eurekia, StenopiIus, Bynumiella. Hardyia and IlIaenurus. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Archaeocyatha from the Lower Cambrian of Wolf Lake and Quiet Lake areas in the Yukon Territory are described and illustrated. The fossils occur in carbonate rocks and are well preserved. Much of the necessary structural detail of the fossils is clearly observed in thin-sections and on polished surfaces of the specimens. The collection contains twenty-three species, twelve of which are new species. The new species described are: Ajacicyathus yukonensis, Coscinocyathus multiporus. Coseinocyathus cassiariensis, Coscinocyathus inequivallug, Coscinocyathus serratus, Coscinocyathus veronicus, Coscinocyathus tubicornus, Carinacyathus perforatus, Pyenoidocyathus solidus, Loculicyathus elliptieus, Metacoscinus poolensis, and Claruscyathus ketzaensis. The genera Carinacyathus and Loculicyathus are reported for the first time in North America. The Yukon fauna is dominated by Coscinocyathidae and Pycnoidocyathidae, showing close relationship to faunae in the Cordilleran region of British Columbia. It also shows relationship to Siberian and Australian faunae. This fauna is very different from the archaeocyathid assemblages in Nevada and California, where the dominant forms are Ethmophyllidae and Ajacicyathiclae. Arehaeocyatha have been instrumental in determining the age of rocks underlying a large area of the Yukon Territory. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.

The Hickory Sandstone Member of the Riley Formation is dominantly quartz sandstone up to 167 m thick which crops out in the Llano Uplift region of central Texas and dips away in all directions. It lies unconformably upon the irregular surface of the Precambrian Texas craton. The association of isopach thicks and thins over cratonic lows and highs demonstrates topographic control of Hickory deposition. Regional subsurface studies delineate the extent of the overlying Cap Mountain Limestone. Beyond the limits of the Cap Mountain, the Hickory grades into the Lion Mountain Sandstone laterally and vertically so that correlations are difficult. The six lithofacies of the Hickory Sandstone were deposited as nonbarred tidally-influenced or estuarine-related equivalents to deposits of Holocene environments. Outer estuarine tidal channel-shoal deposits display abundant channel fills of large-scale foresets, parallel bedded sandstone, and minor siltstone. Trilobite trackways (Cruziana) and resting traces (Rusophycus) occur in these deposits, associated with U-shape burrows (Diplocraterion and Corophioides). Deposits of open coast sandy tidal flats display upward-fining character, medium-to large-scale festoon crossbedding, abundant small-scale ripple bedforms of all types, and mudcracks. These deposits include the U-shape burrows, Corophiodes, and the trackway, Climactichnites. Deposits of inner estuarine tidal channels and tidal flats display upward-fining character, wavy-lenticular bedding, bimodal paleocurrent patterns, and the resting trace, Pelecypodichnus. All of these deposits prograded as a unit until sea level rise shut off sediment supply. Progradation of tidal channel and shoal sediments was renewed. These deposits are festoon crossbedded hematitic sandstone with wavy-lenticular bedding and abundant fossil debris. Storm energy funneled through tidal channels deposited crossbedded sandstone onto the nearshore inlet-influenced shelf. Final Hickory deposits and initial Cap Mountain deposits were storm-dominated, burrowed and laminated calcitic shelf sands. / text

2 v. : maps, plates, 6 fold maps in end pocket ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1977) from the Dept. of Geology and Minerology, University of Adelaide

The Elbrook-Conococheage Formations (Middle to Upper Cambrian) are a kilometer-thick sequence of cyclic, peritidal carbonates that formed an aggraded, rimmed shelf on a mature, passive continental margin. Sedimentation rates for peri tidal carbonate environments far exceeded long term subsidence of the platform (3 to 5 cm/1000 yrs.); thus, the shelf stayed filled to sea level (i.e., was aggraded). Relative sea level rise did exceed sedimentation for brief periods, causing cyclic transgressions (max. 3 m initial submergence). Average cycle duration was 60,000 years. Cycles (1-7 m thick) are composed of basal subtidal/intertidal limestone consisting of bioherms, grainstone and ribbon carbonate; and dolomitic laminite caps containing minor quartz arenite, shale and breccia. Cycle development was controlled by initial submergence increment and position relative to shelf edge. Large initial submergence produced thick subtidal-based cycles representing shelf lagoon and shoal conditions. Small events resulted in submergence within the intertidal zone, which deposited thick, mudcracked intertidal limestones in outerplatform settings, and thick sequences of laminite in inner platform settings. Slopes on the platform were low (less than 3 cm/km); thus, subtidal facies developed in a mosaic pattern of lagoons and shoals, rather than in shore-parallel belts. When low areas filled, tidal flat laminites prograded seaward over subtidal units. Cyclicity may reflect spasmodic subsidence of the shelf, or uniform subsidence overprinted by small-scale glacio-eustatic sea level changes related to shifting patterns of mountain glaciation. Interior areas of Quaternary carbonate shelves are characterized by incipiently drowned facies and are punctuated by soil/caliche horizons and karst surfaces, that reflect 100 rn glacio-eustatic sea 'level fluctuations. In contrast, many ancient shelves, including the Cambre-Ordovician shelf of the Appalachians, were dominated by cyclic peritidal sequences lacking evidence of major sea level events. Aggraded shelves may represent the typical state of mature carbonate continental shelves in the absence of large-scale sea level fluctuations. / M.S.

An interbasinal study of Late Cambrian cyclic carbonate successions in the Appalachian and Cordilleran passive margins, the Texas cratonic embayment and the southern Oklahoma aulacogen has provided controls on the simultaneous development of peritidal to subtidal meter-scale cycles and the larger scale depositional sequences on which they are superimposed. Fining-upward peritidal cycles grade seaward into coarsening-upward, shallow to deep subtidal cycles that form a continuum across the carbonate platforms and are genetically linked to one another by shared lithofacies. Eustacy appears to exert the dominant control on the simultaneous development of peritidal and subtidal cycles on different carbonate platforms. Based on the recognition of dominant periodicities on power spectra derived from time series of subtidal cycles, high frequency eustatic oscillations may be controlled by Milankovitch astronomical rhythms. Interbasinal correlation of Late Cambrian depositional sequences was performed by graphic correlation and the time-equivalent intervals were correlated lithostratigraphically using isochronous biomere boundaries as time datums. Fischer plots of meter-scale cycles define changes in relative sea level based on the amount of extra accommodation space produced by eustacy beyond that provided by subsidence. Residual eustatic curves derived from subsidence analysis are useful for correlating the longer-term Late Cambrian sea level events and changes in the rate of sea level rise and fall can be used to define shorter-term events. Combining the sea level curves defined by Fischer plots and subsidence analysis with paleobathymetric curves of Late Cambrian cyclic strata suggests that the curves may approximate the form of the eustatic sea level curve. A composite "eustatic” sea level curve for the Late Cambrian was created by qualitatively combining the sea level curves defined by the different techniques for each of the four localities. “Eustatic" sea level curves defined by Fischer plots and subsidence analysis may be used to apply sequence stratigraphic concepts to onedimensional outcrop sections. Combined with systematic changes in the stacking patterns of meter-scale cycles, they can be used to define the internal composition of systems tracts, sequence boundaries, and flooding surfaces of third-order depositional sequences. One- and two-dimensional models of peritidal and subtidal cycle development indicate that peritidal cycle thickness is primarily controlled by accommodation space and deeper subtidal cycle thickness is primarily controlled by sedimentation rate. Whereas lithofacies within peritidal cycles alternate in response to fluctuations in sea level, subtidal cycle development may be related to fluctuations in fairweather and storm wave base that oscillate in harmony with sea level fluctuations. / Ph. D.

A morphometric analysis of Cambrian trilobites shows that extinction events sharply reduced the morphological diversity of ptychopariid trilobites living on the shelf at the lower boundaries of the Marjumiid, Pterocephaltid, and Ptychaspid biomeres (Middle to Upper Cambrian). These extinction events not only separate the trilobite assemblages that characterize each biomere, but they also separate similar sequences of morphological diversification. During the initial deposition of each biomere, the shelf was repopulated by a limited number of ptychopariid species that had similar morphologies of very limited range and type. These initial faunas then underwent a morphological diversification evolving similar morphologies during the deposition of the remainder of each biomere. This pattern of repeating episodes that begin with similar morphologies of trilobites which then undergo similar morphological diversifications suggests that the extinction events at the base of each biomere limited the range of morphologies from which new taxa could evolve. Each new biomere assemblage was unable to build upon the adaptations of the specialized taxa of the previous biomere. Only the limited range of similar morphologies of the initial repopulating trilobites was the source from which new taxa could evolve. As a result, new taxa “reevolved the wheel” each time they became adapted to the vacated habitats that were previously occupied in the underlying biomere. In contrast, near the Cambrian-Ordovician boundary, the extinction event at the base of the Lower Ordovician Symphysurinid biomere did not reduce the range of morphologies as drastically as the previous biomere extinctions in the Cambrian. A more diverse initial fauna occurs in the Symphysurinid biomere. This fauna did not undergo a morphological diversification during deposition of the biomere and some regions of morphospace previously occupied in the Cambrian were not reoccupied in this biomere. Taxa of the lower Ordovician were relatively canalized in their morphology. In the Marjumiid biomere (Middle to lower Upper Cambrian), the morphological diversification of ptychoparid trilobites was not significantly influenced by either paleogeography, depositional settings, or migration of taxa from outside North America. The morphological diversification of the ptychopariid assemblage is also seen in a subset of ptychopariids that consists of the Superfamilies Raymondinacea, Asaphiscacea, and Marjumiacea. These superfamilies are the numerically abundant and most diverse taxonomic groups in the Marjumiuid biomere. The patterns of morphological diversification in both the Order Ptychopariida and the combined assemblages of the Superfamilies Raymondinacea, Asaphiscacea, and Marjumiacea were relatively consistent among different paleogeographic regions and were not influenced by general lithofacies. The consistency of the regional patterns and the lack of influence of general lithofacies on these patterns indicate that the overall pattern of morphological diversification is the result of in situ evolution of taxa within the North American Craton and not the result of shifting biofacies or the migration of taxa from outside North America. The morphological diversification of ptychoparids in the Marjumiid Biomere is composed of two distinct phases. The morphological expansion of the Superfamily Ptychopariacea (the ehmaniellids) in the Ehmaniella Biozone is an early phase of diversification. The morphological expansion of the Superfamilies Norwoodiacea, Solenopleuracea (exclusive of the Family Solenopleuracea), Asaphiscacea, Raymondinacea, and Marjumiacea in the Bolaspidella to Crepicephalus biozones represent the later phase of diversification. This second phase is also composed of two morphological expansions, an early expansion in the Superfamilies Norwoodiacea and Solenopleuracea in the Bolaspidella and Cedaria biozones, and a later expansion in the Superfamilies Asaphiscacea, Raymondinacea, and Marjumiacea in the Cedaria and Crepicephalus biozones. The ptychopariid assemblages of the younger Ptychaspid biomere (Upper Cambrian) also display a two-phase morphological diversification. / Ph. D.