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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Stratigraphic implications of the spatial and temporal variability in sediment transport in rivers, deltas and shelf margins

Petter, Andrew Lucas, 1980- 29 September 2010 (has links)
Sediment delivery to a basin exerts a first-order control over sedimentation, and therefore study of sedimentary rocks can reveal information about the nature of sediment delivery in the past. This dissertation examines several aspects of this problem using experimental, outcrop, and subsurface data. Flume experiments were undertaken to test the combined effects of autogenic alluvial aggradation and forced regression on the development of fluviodeltaic stratigraphy. Alluvial aggradation occurred in response to steady relative sea-level fall, and eventually consumed the entire sediment budget as the river lengthened in response to forced regression. The Campanian Lower Castlegate Sandstone (Utah) was studied as a potential ancient analog resulting from similar autogenic behaviors as observed in the experiments. Extensive measurement of grain-size distributions and paleo-flow depths from outcrop were utilized to explore downstream changes in paleo-hydraulics of the ancient fluvial systems in the Lower Castlegate in response to extensive alluvial aggradation and consequent loss of sediment from transport. An interesting finding was the stratigraphic signature of backwater hydraulic conditions in the distal reaches of the Lower Castlegate paleo-rivers. Finally, a simple and novel inversion scheme was developed for estimating paleo-sediment flux from ancient shelf-margin successions. An advantage of the methodology is that it allows for both spatial and temporal reconstruction of paleo-sediment flux patterns. The inversion scheme was applied to shelf-margin successions in the Washakie-Sand Wash Basin of Wyoming, the New Jersey Atlantic margin, the North Slope of Alaska, and the Zambezi margin of East Africa using published subsurface datasets. The Neogene passive margins within the studied datasets were found to consistently deposit around one-third of their total sediment budget on the shelf-margin topset, and bypass two-thirds of their budget beyond the shelf edge. The implications of this finding on the flux of terrestrial-derived particulate organic carbon (POC) from rivers to the ocean were explored, and a long-term average flux of POC to deepwater storage was estimated. The sediment-flux inversion scheme was also applied to derive input parameters for stratigraphic modeling of the Ebro margin. The modeling results indicate that the autostratigraphic behavior of the margin may have been previously underestimated. / text
2

High-frequency tectonic sequences in the Campanian Castlegate Formation during a transition from the Sevier to Laramide orogeny, Utah, U.S.A.

Cross, David B 13 May 2016 (has links)
Though stratigraphic correlations are abundant in the Cordilleran basin-fill, they rarely include along-strike transects providing a spatio-temporal sense of deformation, sediment-supply and subsidence. A new, high-resolution, regional strike-correlation of the Castlegate Formation reveals progressive northward-growth of the San Rafael Swell during two embryonic episodes of Laramide-style deformation in central Utah. The intrabasinal deformation-events produced gentle lithospheric-folding punctuated by erosional-truncation of upwarped regions. The earliest episode occurred at 78 Ma in the southern San Rafael Swell likely causing soft-sediment deformation and stratal-tilting. Following this the alluvial-plain was leveled and rapid, extensive-progradation took place. A second episode, at 75 Ma, where deformation was focused in the northern San Rafael Swell, also caused sediment-liquefaction and erosional beveling. The stratal-tilting and sediment-liquefaction is attributed to seismicity induced by basal-traction between a subducting flat-slab and continental-lithosphere. The south-to north time-transgression of uplift is spatio-temporally consistent with NE-propagation of an oceanic-plateau subducted shallowly beneath the region.

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