The Monkton Formation of the western shelf stratigraphic sequence in Vermont (VT) is identified as a Lower Cambrian regressive sandstone unit containing parasequences recording tidal flat progradation. Previous workers identified cycles believed to represent parasequences in a portion of a 1034' deep geothermal well drilled at Champlain College in Burlington, Vermont. For this study, both outcrop and well geophysical surveys were completed to better identify gamma emission curves and relative values for parasequences and select lithologies that are indicators of bathymetry and sea level. After using physical stratigraphic techniques to assemble a composite stratigraphic section for the Monkton Formation, analysis of the gamma emission curve and relative gamma values resulted in the identification and characterization of parasequences and select lithologies within the Monkton. Interpretation of bathymetry-sensitive lithologies along with parasequence architecture and thickness trends reveals three distinctive intervals over the thickness of the Monkton. It is recognized that the succession of these intervals represents an overall decreasing rate in accommodation space generation through Monkton deposition. Previous workers have suggested that biostratigraphic relationships of the Monkton Formation to the Potsdam Group in New York (NY) suggest that that they would be at least partially correlative. To further refine age relationships and constrain and compare the provenance of the Vermont stratigraphy locally and regionally, zircon samples were collected from the Monkton and the overlying Danby Formations and radiometric age determinations were completed by laser ablation–inductively coupled plasma mass spectrometry (LA-ICPMS) at University of Arizona Laserchron Center. Zircon age probability distribution curves show two dominate age peaks between 1.05-1.09 Ga and 1.15-1.18 Ga for the Monkton and Danby suggesting either a continuity of provenance through the Cambrian or the cycling of the Monkton's sand. The 1.05-1.09 Ga age range corresponds to rocks generated during the Ottawan Orogeny while the 1.15-1.18 Ga range is associated with the Shawinigan Orogeny and anorthosite-mangerite-charnockite-granite (AMCG) plutonism. Dominant age peaks in the Vermont samples between 1.15-1.18 Ga are similar to the 1.16 Ga age peak reported by other workers from the Altona and Ausable Formations of the Potsdam Group of New York. The shared dominant age peak and close proximity of the Vermont and New York stratigraphy may suggest a primarily shared provenance.

Previously unreported silicified trilobite faunas occur in a narrow stratigraphic interval of the Upper Cambrian (Sunwaptan) St. Charles Formation in the Bear River Range of southeastern Idaho. The faunas occur in four closely spaced rudstones and trilobite packstones indicating deposition in a shallow subtidal setting above storm wave base. At least 23 species are represented, included two undescribed genera and several undescribed species. The faunas are notable for their high trilobite abundance and pervasive silicification. Most coeval faunas have been described on the basis of small numbers of "crack-out" specimens, and the new material reveals many details of anatomy, including knowledge of most exoskeletal sclerites. The four trilobite-yielding beds contain markedly different taxon-abundance profiles, yet most species are shared between them. This suggests multiple, taphonomically-controlled samples of a similar underlying distribution, though true ecological variation cannot be discounted.

This study implies a survey of a somewhat unexplored Cambrian carbonate formation in the Argentine Precordillera (AP) located in western Argentina, close to the city of San José de Jáchal. The carbonate platform of the AP is a unique piece of the South American geology and is in this study partly surveyed and compared with the Stephen Formation of northern Canada, a middle Cambrian unit renowned for its contents of exceptionally well preserved soft bodied fossils named the Burgess Shale biota. The investigated formation consists of an olistolith among the several Los Túneles Olistoliths at the Western Precordillera. The olistolith originates from the Cambrian Period and lies embedded in younger material with an age and history up for debate by several paleontologists and biostratigraphers. Shallow investigations have shown that these rocks may have similar properties to rocks of the Stephen Formation. There are only a few known rock assemblages on Earth showing Burgess Shale-type (BST) preservation and if the Los Túneles Olistolith proves to possess BST preservation it would be of great substance for the geological researchers of Argentina. The olistolith has in this study been explored by gathering samples in field and dissolving them in acid to investigate possible fossil content. The aim is thus to ascertain whether or not the Los Túneles Olistolith may contain especially well preserved fossils. This is the first study ever made of the microfauna in a middle Cambrian unit in the whole of South America, and hence it will tell if further investigations would be of interest. This survey determines that the Los Túneles Olistolith actually consists of three olistoliths encased in matrix, do not contain BST preservation and that further studies are not probable to show otherwise. The fossil findings, such as Chancelloriidae Chancelloria, Hexactinellida Recticulosa and Mollusca Hyolitha establish that the three Los Túneles Olistoliths originate from middle Cambrian while the matrix surrounding the olistolith is determined to be of Devonian age. / Den här studien är den första undersökningen någonsin som fokuserar på mikrofauna i sedimentära avlagringar från mellersta kambrium i Sydamerika. Studien utreder en tidigare bara ytligt utforskad kalkstensformation i västra Argentina, nära staden San José de Jáchal, i den argentinska precordilleran. Formationen, med namnet Los Sombreros Formationen, innehåller olistoliter från kambrium som undersökts och jämförts med den välkända Stephen Formation från norra Kanada, en formation som är känd för att innehålla exceptionellt välbevarade mjukdelar av fossil, kallat the Burgess Shale Biota. Syftet med studien är att fastställa huruvida Los Túneles Olistoliterna har potential att innehålla välbevarade fossil samt att utreda ifall ytterligare undersökningar är av intresse eller ej.                       Studien fokuserar på vad som tidigare trotts vara en av olistoliterna bland Los Túneles Olistoliterna, som är en del av Los Sombreros Formationen, men som i denna studie visat sig egentligen vara tre olika olistoliter som avsatts intill varandra. Tidigare ytliga undersökningar har visat att dessa olistoliter skulle kunna innehålla liknande fossil som the Stephen Formation. Det finns bara ett fåtal platser i världen där så pass exceptionellt välbevarade fossil tidigare hittats och om Los Túneles Olistoliterna skulle visa sig vara ett nytt fynd skulle det vara av betydelse för den fortsatta geologiska forskningen i Argentina. Genom insamling av prover som upplösts i syra och sedan undersökts i mikroskop har slutsatsen dragits att Los Túneles Olistoliterna inte innehåller Burgess Shale Biota och att ytterligare undersökningar förmodligen inte kommer visa annorlunda resultat. Fossilfynden som har gjorts, så som Chancelloriidae Chancelloria, Hexactinellida Recticulosa och Mollusca Hyolitha fastställer att de tre Los Túneles Olistoliterna härstammar från mellersta kambrium medan omkringliggande material kommer från Devon. / Este estudio se enfoca en un área poco explorada de una formación que aloja olistolitos carbonaticos del Cámbrico y Ordovícico situado en la Precordillera de Argentina en el oeste del país, cerca de San José de Jáchal, Provincia de San Juan. La plataforma carbonatada de la precordillera es una parte única de la geología de Sudamérica y es en esta investigación parcialmente estudiada y comparada con la Formación Stephen en el norte de Canadá, una unidad del Cámbrico Medio famosa por su contenido de fósiles excepcionalmente bien preservados llamado the Burgess Shale biota.                       La investigación se ha enfocado en un olistolito entre los varios que aparecen en el sector Los Túneles en el norte de la Precordillera de San Juan, oeste de Argentina. De este olistolito sa ha recuperado macrofauna indicativa del período Cámbrico. Este olistolito está alojado en rocas clásticas cuya una edad que es todavía un tema de debate entre paleontólogos y bioestratigrafos. Investigaciones superficiales han mostrado que estas rocas pueden tener los mismos atributos que las rocas de la Formación Stephen. Solo hay unas pocas formaciones sedimentarias en la Tierra que mantienen preservación del tipo de Burgess Shale (BST) y si el olistolito de estudio de la sección de Los Túneles presenta preservación de BST va a tener gran importancia para la Geología de Argentina. El estudio ha incluido un muestreo de campo de varios olistolitos, posterior tratamiento químico (desagregación física y química de las calizas en ácido para investigar possible contenido de microfósiles), y finalmente”picking” bajo lupa binocular para rescatar micropiezas fósiles. El objetivo de este es comprobar si el olistolito de la sección de Los Túneles puede tener fósiles especialmente bien preservados. Este estudio es el primer estudio de la micro fauna del Cámbrico medio en el conjunto de Sudamérica y de ahí que lo indicará si estudios adicionales serían de interés.                       Este investigación determina que el olistolito en Los Túneles Olistolitos en realidad consiste en tres olistolitos encerrados en matriz, contiene fósiles sin una preservación BST y por tanto estudios adicionales no son requeridos para demostrar lo contrario. Los hallazgos fósiles, por ejemplo Chancelloriidae Chancelloria, Hexactinellida Recticulosa y Mollusca Hyolitha, establezca que los tres olistolitos de Los Túneles Olistolitos son de Cámbrico Medio y la matriz que rodea a los olistolitos de periódo Devónico.

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

No description available.

The emergence and radiation of metazoan body plans around the Precambrian/Cambrian boundary, some 500-600 million years ago, seems to be concordant with the appearance and diversification of preservable hard parts. Several Precambrian soft-bodied, multicellular organisms most likely represent stem-group bilaterians, but their fossil record is rather sparse.  In contrast, the Cambrian fossil record is comparably rich – comprising hard part, trace fossil and delicate soft tissue preservation – and most animal phyla that we know of today had evolved by the end of the Cambrian. Consequently, this time represents an important period in the early evolution of metazoan life forms. Most skeletal remnants of invertebrate organisms from this period are preserved in incomplete, disarticulated sclerite assemblages, and the true architecture of the original skeletal structure, the scleritome, may therefore be hard to discern. Many scleritomous taxa have been suggested to be members of the lophotrochozoan clade, while their exact position within this group remains unclear. Such taxa are often referred to as Problematica. This thesis deals with some problematic scleritomous early Cambrian lophotrochozoans, and as such also addresses the dilemmas of scleritome reconstructions. In the first part, completely disarticulated calcareous sclerites from the lower Cambrian of North Greenland are described as Trachyplax arctica. Hypothetical scleritome reconstruction alternatives and comparisons to other scleritome-bearing taxa are discussed, but the lack of articulated material obscures any satisfactory conclusions regarding phylogenetic affinities and the original morphology of the organism. The other part of the thesis focuses on some minute, organophosphatic scleritomous metazoans, tommotiids, found in lower Cambrian limestone successions in South Australia – Paterimitra pyramidalis and Kulparina rostrata – their scleritome architecture and their phylogenetic relationship with paterinid brachiopods. The oldest brachiopod from South Australia, Askepasma saproconcha, and the slightly younger Askepasma toddense are also described and discussed. Based on articulated specimens, recently described partial scleritomes of the tommotiid Eccentrotheca helenia and similarities in shell ultrastructure with both Eccentrotheca and Askepasma, Paterimitra is interpreted as a stem-group brachiopod and reconstructed as a bilaterally symmetrical, sessile, filter feeder with a tubular/conical scleritome. The morphological similarities with Paterimitra point in the same direction for the slightly older Kulparina.

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 majority of the Middle Cambrian Wheeler Formation in the Drum Mountains was deposited during a single 3rd order sequence. Superimposed onto this sequence are three indistinct 4th order cycles and twenty distinct 5th order cycles. These higher other cycles were likely deposited within short intervals of geologic time (204 to 405 ky). The lower sequence boundary zone occurs within the Swasey Formation. The Transgressive Surface is the contact between the Swaset and Wheeler Formations. The Maximum Flooding Surface is located near the top of the lower Wheeler Formation, which also approximates the base of the Ptychagnostus atavus range zone. The upper sequence boundary is marked by stromatolites, which occur near the top of the upper member of the Wheeler Formation in the Drum Mountains. Deposition of the Wheeler Formation in the Drum Mountains was controlled by eustacy and tectonics. Local normal faulting associated with Middle Cambrian postrifting thermal subsidence may have caused some of the 5th order cycles. The cycles and surfaces defined in this stratigraphic analysis, and the base of the Ptychagnostus atavus and P. gibbus range-zones, can be used to correlate strata occurring in other localities in the eastern Great Basin. In addition, this study enables the evaluation of the effect of tectonics (faulting) versus global eustacy on the sedimentary regime occurring within the Middle Cambrian House Range Embayment. (95 pages)

The Bloomington Formation (~425 m thick) is a latest Middle Cambrian (~506.5-505 Ma), mixed, warm water, continental-shelf carbonate and fine-grained siliciclastic unit on the Cordilleran passive margin exposed in northern Utah and southern Idaho. Thicknesses of the Bloomington Formation at Calls Fort Canyon are 111 m in the Hodges Shale Member, 230 m in the middle limestone Member, and 84 m in the Calls Fort Shale Member. The Hodges Shale and Calls Fort Shale Members are shale dominated and represent outer detrital belt deposition. The Logan Canyon outcrop of the Hodges Shale Member shows an environmental change that may represent a transition form an open marine facies into what appears to be a lagoonal facies. The middle limestone member represents shallow marine carbonate deposition on the passive margin shelf. The Bloomington Formation has a low fossil abundance and diversity when compared to correlative units such as the Wheeler and Marjum Formations. There are, however, 10-50 cm thrombolite bioherms, associated with Girvanella oncoliths. These bioherms indicate a shallow-water carbonate facies that experienced a small flooding event that gives the bioherms time and proper conditions to build up. δ18O and δ13C results both show positive and negative shifts with δ13CVPDB values of 1.0 to -4.7 per mil and δ18OVSMOW values of -12.9 to -20.8 per mil. A negative δ13C excursion in the Hodges Shale may correlate to a similar excursion in the base of the Wheeler Formation that represents the DICE event. Lower and Middle Cambrian Formations in the Wellsville Range have been interpreted as being part of a second order transgressive system and containing third and higher-order cycles. The contact of the Hodges Shale Member and the underlying Blacksmith Dolomite represents a flooding surface and a sequence boundary, followed by a third order cycle. Flooding is indicated by shale deposits that overlie carbonates with a shallowing upward trend. High frequency fourth or fifth order cycles are expressed as laminated shale and thick-bedded limestones as well as thick packages of interbedded, thin limestones and shales. A PCA analysis of thin section point counts indicates that the limestone lithologies of all three members repeat throughout the entire Formation, suggesting cycles of relative sea level rise that cause repeating facies.

The Blacksmith Formation of Middle Cambrian (Albertan) age was studied in southeastern Idaho and northernmost Utah. Lithology and sedimentary structures were compared with modern environments and ancient rocks to determine environments of deposition, paleo-geography, diagenetic alterations and patterns of dolomitization. The Blacksmith Formation can be divided into five basic rock types. Rock type A has cryptalgalaminae, nrudcracks, and lacks bioturbation. Rock type A is inferred to have been deposited in the upper intertidal to supratidal environment. Rock type Bis extremely dolomitized and brecciated. It is inferred that rock type B was deposited in the upper intertidal to supratidal environment. Rock type C may have cryptalgal mats, stromatolites consisting of laterally linked hemispheroids, birdseye structures, vertical burrows and pseudomorphs after evaporite minerals. Rock type C is inferred to have been deposited in the lower intertidal environment. Rock type D is fine grained, often dark gray in color, has trails and often contains fossil fragments. Rock type Dis inferred to have been deposited in subtidal-lagoon or open-platform environments. Rock type Eis ooid-rich, and is often cross-stratified. Rock type Eis inferred to have been deposited in an agitated-shoal or quiet-water shoal environment. All rocks of the Blacksmith Formation were deposited in supratidal to shallow subtidal environments. During Albertan time the study area was located in the tropics, and the adjacent area had little relief. Clay mineralogy of the insoluble residues suggests a relatively humid paleoclimate. Tidal amplitude was probably low, as suggested by ·small algal domes, LLH strornatolites, and cryptalgal mats. Water depth varied throughout the area. Less restricted fauna to the north suggest that water depth increased to the north. It is inferred that a transgression from the west, regression to the west, a second transgression, and possibly a second regression controlled the distribution of facies. Early diagenesis included minor compaction of intertidal or very shallow subtidal deposits, whereas deeper subtidal deposits may have undergone more compaction. Cementation occurred early in the inter-tidal or shallow subtidal environment. Dolomitization of the Blacksmith by a hypersaline brine is suggested by pseudomorphs after evaporites, authigenic quartz, desiccation features and cloudy dolomite rhombs. Chemical analyses for sodium also indicate a hypersaline fluid. The association of some of the dolomite with the oolite-shoal environment suggests that the dolomite distribution may be in part facies-controlled. The hypersaline brine likely developed on tidal flats south of the area, and percolated through the sediments via refluxion and through the permeable sediments via hydrostatic head. The amount of dolomite decreases to the north, farther from the source of the brine. As the dolomitizing brine moved downward, the Mg/Ca ratio was lowered so that a ferroan dolomite formed in the subsurface, under reducing conditions. Late diagenetic events include aggrading neoroorphism by low-Mg calcite which may obliterate grains and cement or preserve grains and episodes of cementation. Late dolomitization, producing coarse dolomite rhombs exhibiting undulose extinction and curved crystal faces may have been epigenetic in origin.