No description available.

Biogenic structures can impart important information regarding animal behaviors and depositional conditions at the time of colonization including: sedimentation rate, current velocities, distribution of food resources, oxygenation, salinity, and temperature. This thesis utilizes various ichnological subdisciplines to build upon these underlying ichnological principles. Neoichnology is a newly emerging field that can provide invaluable information about modern and ancient organisms. Burrowing activities of a population of deposit-feeding, freshwater Limnodrilus and Tubifex is found to produce biogenic graded bedding. Similarly, the burrowing activities of Euzonus mucronata are studied in relation to the trace fossil Macaronichnus segregatis, which displays mineralogical segregation between the burrow infill and mantle. The process of grain partitioning was assessed using videographic analyses of ingested and excreted grains by these deposit-feeding polychaetes, which selectively ingest felsic grains through en-masse feeding in felsic-rich locales. Macaronichnus is an important trace in ancient deposits of nearshore settings; however, since its inception, the genus had not been formally diagnosed. Accordingly, a unique approach to classification of these traces was undertaken, using grain sorting and collective morphology as ichnotaxobases, in addition to the diagnosis of a new, related genusHarenaparietis. In the Permian Snapper Point Formation of SE Australia, a new ichnospecies of Piscichnus was diagnosed and interpreted to reflect fish or cephalopod feeding via hydraulic jetting into the substrate in search of infaunal food sources. The delineation of trace fossils through ichnotaxonomy provides a basis for identifying trace fossil suites, which can be interpreted through ichnofacies analysis. Subtle ichnological and sedimentological attributes of deltaic strata in the Viking Formation permits the identification of wave-influenced and mixed river- and wave-influenced deposits in the Hamilton Lake and Wayne-Rosedale-Chain areas of Alberta, Canada, respectively. Facies analysis combined with the identification of palimpsest stratigraphic surfaces led to the identification of transgressively incised shoreface deposits at Hamilton Lake. Examples of palimpsest ichnofossils from the Hamilton Lake area and from other strata are used in an assessment of soft-, stiff- and firmground suites. This study revealed the importance of substrate properties, environment, stratigraphy and processes leading to the formation and expression of allocyclic and autocyclic surfaces.

No description available.

For decades the Upper Cretaceous Lower Tuscaloosa Formation of the U.S. Gulf Coast has been considered an onshore hydrocarbon play with no equivalent offshore deposits. A better understanding of the Lower Tuscaloosa sequence stratigraphic and paleogeographic framework, source-to-sink depositional environments, magnitude of fluvial systems, regional trends in reservoir quality, and structural influences on its deposition along with newly acquired data from offshore wells has changed this decades-long paradigm of the Lower Tuscaloosa as simply an onshore play. The mid-Cenomanian unconformity, underlying the Lower Tuscaloosa, formed an extensive regional network of incised valleys. This incision and accompanying low accommodation allowed for sediment bypass and deposition of over 330 m thick gravity-driven sand-rich deposits over 400 km from their equivalent shelf edge. Subsequently a transgressive systems tract comprised of four fluvial sequences in the Lower Tuscaloosa Massive sand and an overlying estuarine sequence (Stringer sand) filled the incised valleys. Both wave- and tide-dominated deltaic facies of the Lower Tuscaloosa are located at the mouths of incised valleys proximal to the shelf edge. Deltaic and estuarine depositional environments were interpreted from impoverished trace fossil suites of the Cruziana Ichnofacies and detailed sedimentological observations. The location and trend of valleys are controlled by basement structures. Lower Tuscaloosa rivers were 3.8m – 7.8m deep and 145m – 721m wide comparable to the Siwalik Group outcrop and the modern Missouri River. These systems were capable of transporting large amounts of sediment indicating the Lower Tuscaloosa was capable of transporting large amounts of sediments to the shelf edge for resedimentation into the deep offshore. Anomalously high porosity (>25%) and permeability (>1200md) in the Lower Tuscaloosa at stratigraphic depths below 20,000 ft. are influenced by chlorite coating the detrital grains. Chlorite coatings block quartz nucleation sites inhibiting quartz cementation. Chlorite coats in the Lower Tuscaloosa are controlled by the presence and abundance of volcanic rock fragments supplying the ions needed for the formation of chlorite. Chlorite decrease to the east in sediments derived from the Appalachian Mountains. An increase in chlorite in westward samples correlates with an increase of volcanic rock fragments derived from the Ouachita Mountains. / text

During the Late Pliocene and early Pleistocene, when the paleo-Orinoco delta system transited over the Amacuro Shelf and reached the paleo-shelf-break along the southeastern shoreline of Trinidad. At this time onwards, the shelf-edge delta clinoforms developed further eastward. These deltaic clastic wedges serve as the unique analog in the geological record for an accommodation-driven inner-shelf and shelf-edge delta, developed at an oblique foreland tectonic setting situated at a tropical-equatorial paleogeographic setting. These deposits were influenced by strong Atlantic longshore current, tropical storms, and phytodetrital pulses, and with an exceptionally high sediment accumulation rates. These four aspects make the clastic wedges unique candidates for sedimentological, ichnological, and stratigraphic investigation. The primary objectives of this thesis are to: (a) collect, analyze, and integrate outcrop data on lithofacies, trace fossils, and discontinuity surfaces into a comprehensive depositional and ichnological model for the first growth-fault-guided shelf-marginal pulse of the paleo-Orinoco delta, as recorded in the Mayaro Formation outcrops in southeast Trinidad; and (b) deduce the dominant sedimentary processes during the across shelf transit and their impacts on the benthic infauna as preserved in the Morne L’Enfer Formation outcrops of southwest Trinidad, which are possibly slightly older than the Mayaro Formation. The basal interval of the Morne L’Enfer Formation has specifically been investigated for this purpose, where the deltaic clastic wedges are preserved directly above shelf deposits. The entire Mayaro Formation megasequence is categorized into deposits belonging to twelve different subenvironments based on lithofacies associations and ichnological characteristics. Ichnological evidence indicates that the shelf-edge deltas are one of the most extreme marine environments for benthic metazoans to colonize. However, the combinations and ranking of stress factors affecting the colonizing fauna are diverse and distinct in every individual subenvironment indicating the relative dominances of river-influence, waves, and/or sediment-gravity-flows vis-à-vis slope instability. Due to variations in stress factors, the megasequence also displays dual ichnologic and sedimentologic properties of both the shelf-edge delta lobe(s) and the outer shelf delta lobe(s). A minor transient tidal influence can only be observed in the architectural elements, e.g. elongated interbar embayment and interlobe prodeltaic depocentres, which control topography and enhance tidal effect. Discovery of an unusual monospecific Glossifungites Ichnofacies along an incision surface in the midst of the Mayaro Formation succession enabled a substantial overhaul of the earlier understanding of the formation in terms of its depositional model and stacking pattern. The surface has been re-identified as a canyon/gully cut at the shelf-edge, which possibly acted as a conduit for (a) the mass movements and for (b) the coarse clastic (mostly silt to medium-grained sand) sediment transfer to deep marine settings. The monospecific nature of the Glossifungites Ichnofacies suite indicates that the incision surface was under substantial ecological stresses for the colonizing infauna. The stresses might have arisen from slope instability of the steep canyon/gully walls, mass movements above the incision surface, elevated water turbulence, and lowered salinity from river influx. Five different facies tracts have been identified within the canyon/gully-fill, which crosscuts the shelf-edge delta-front. The facies tracts are dominated by different types of sediment-gravity flow deposits, which are systematically stacked and are almost devoid of trace fossils due to rapid sedimentation rates and slope instability. They are also strikingly different from the surrounding deltaic facies. A high-frequency sequence stratigraphic model involving the influence of growth-fault tectonics on the relative sea-level curve has been invoked to explain the incision of the canyon/gully and its sequential filling processes. On the other hand, the transition from the open shelf to inner-shelf deltaic condition as displayed by the basal members of the Morne L’Enfer Formation is strongly dominated by evidences of river influence with the transient background action of fair-weather waves and storm waves. A peculiar pattern of disappearance of trace fossils produced by irregular sea-urchins highlight that the river influence was quite strong not only at the sediment-water interface but also in the water-column, which affected invertebrate larvae. The initial progradation of the clastic wedge on the shelf was dominated by hyperpycnal flows and waves in contrast to tidal domination in the younger members of the formation.