The modern insular shelf and slope of western Puerto Rico is characterized by reef carbonate and siliciclastic sedimentary environments controlled by the complex interplay of tectonic arching and faulting, vigorous erosion of the elevated island of Puerto Rico, fluvial incision and sedimentation pulses, reef growth, and rapid late Quaternary eustatic sea-level changes. For this study, I interpret 725 km of high-resolution, single-channel seismic lines that were collected over the western insular shelf and slope by the RV Isla Magueyes in 2000 to better understand tectonic, erosional, and eustatic controls on late Quaternary history. The seafloor geology of the western shelf and slope area of Puerto Rico has been well studied and mapped mainly from grab and short cores collected by geoscientists at the U.S. Geological Survey and at the University of Puerto Rico at Mayagü̈ez. Because of low tectonic uplift rates from the western coast of Puerto Rico, the onland late Quaternary sedimentary history is not recorded in Quaternary coastal outcrops. The results of my seismic interpretation and correlation with multi-channel seismic data collected in 1972, reveal four main units defined by characteristic stratal reflection terminations and seismic facies. These units include: Unit 1 (basement) - a gently folded and faulted basal section correlated to the Oligocene-early Pleistocene carbonate shelf of Puerto Rico; deeper penetration, industry multi-channel seismic lines show that these rocks are deformed in a broad east-west-trending arch; Unit 2 (lowstand systems tract, LST) - chaotic channel fill deposits filling deep (~ 30 meter) incisions formed during the Last Glacial Maximum about 20 ka; Unit 3 (transgressive system tract, TST) - poorly stratified deposits truncating the top of Unit 2 and deposited during early Holocene transgression of the shelf margin; Unit 4 (highstand system tract, HST) - late Holocene, highly stratified deposits related to aggradation as the Holocene transgression began to slow. The base of unit 4 is a downlap surface interpreted as a maximum flooding surface likely formed about 8 ka. East-northeast-striking faults are observed that offset the late Quaternary units in three separate zones off the west coast of Puerto Rico. Because of a lack of wells and long cores from the shelf and slope area, age estimates for the four units are based on correlations with sea-level curves derived from dated coral samples in the Caribbean and western Atlantic region. All four units are deformed by faulting that should be considered active and possibly hazardous for the rapidly developing west coast of Puerto Rico. In one area, a large, late Holocene-slump (~ 0.016 km³) is mapped using seismic, sidescan sonar and bathymetric data. Onland continuations of these faults are likely, but have not been identified due to cultural overprint of natural scarps on late Quaternary floodplains. / text

The Dona and Roberts Bay watershed comprises one of the five major watersheds in Sarasota County, Florida. It is connected to the Gulf of Mexico via Venice Inlet. Like many estuaries in the Florida, significant modifications have been made to the drainage basins, principally to the main tributaries. The system has undergone several anthropogenic modifications to enhance water management efforts. Creeks that comprise fresh water input into the system have been dammed in order to inhibit the upstream flow of salt water during the dry season. They are also deepened or lengthened to allow for better drainage. In addition, biogenic activity has also had morphological effects on the system. There are numerous oyster bars, and mangrove forests that impose obstruction to the tidal and river flows. This has resulted in a highly complicated estuary system in terms of flow velocities and sedimentation patterns. The objectives of this study are to quantify the sediment characteristics and deposition-erosion trends and their relationship to flow patterns and other natural and anthropogenic factors within the system. A detailed sedimentary analysis was conducted based on 149 surface sediment samples and 29 drill cores. Spatial distribution of the sediment properties is quite complex, controlled by several interactive factors including; local sediment supply, intensity of the hydrodynamic processes, distribution of oyster bars and mangrove islands, and artificial structures. Sedimentation and erosion is significantly influenced by flood events. In some locations, such as the mouth of the fluvial channels, or the confluence of two creeks, the core data suggest that rapid sedimentation, driven by flood events, is responsible for the development of some of the large shoals. A 2-D depth-averaged circulation model was established for the study area. Many of the natural structures and artificial modifications to the watershed system are incorporated into the model. A close relationship between the flow intensity and sediment characteristics, and therefore, sedimentation-erosion tendency is identified. Remotely sensed data is also incorporated into the study in order to gain an understanding of the development of the estuary system over a ten-year period. Data suggests that the maturation of biogenic organisms that inhabit the system coincides with the development of complex sedimentation patterns.

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The Xigaze forearc basin in southern Tibet, one of the largest and best-preserved forearc basins on Earth, records upper-plate processes active prior to and following the inter-continental collision between India and Asia. However, the understanding of the timing and mechanisms of forearc development and its evolution following collision is spatially and temporally limited. Fundamental questions remain concerning how the basin formed, its paleogeography prior to collision, its subsidence history and the thermal history of the basin following the initial and ongoing continent-continent collision. Answering these questions is important to reconstructing upper plate dynamics during active subduction of oceanic and continental lithosphere. This dissertation addresses the Early Cretaceous to Pliocene history of the Xigaze forearc, using field mapping, sedimentology, sandstone modal petrography, geohistory analysis, U-Pb detrital zircon geochronology, and low-temperature thermochronology (apatite and zircon (U-Th/He)). Appendix A documents the sedimentology and stratigraphy of Lower Cretaceous to Paleocene strata to identify the relationship between the Yarlung-Tsangpo ophiolite and Xigaze forearc basin, reconstruct the sedimentary environments of the southern margin of Asia during the initial to middle stages of forearc deposition, and use the basin history to evaluate the mechanisms controlling forearc subsidence. In Appendix B, analysis of Eocene sedimentary strata, the youngest preserved in the forearc basin, constrains the timing of collision between Asia and the Tethyan Himalaya (India) to be no later than 58-54 Ma based on the similarity of the U-Pb detrital zircon age spectra and sandstone compositions between the Xigaze forearc and strata deposited atop the passive margin of the Tethyan Himalayan at that time. Apatite and zircon (U-Th)/He thermochronologic results in Appendix C constrain the maximum burial temperature of the basin following collision to ~140-200 °C, which corresponds to depths attainable by sedimentation in the forearc and a Paleogene forearc successor basin. This integrated dataset also identifies the initial stage of post-collisional exhumation during the Early Miocene (~ 20-15 Ma), followed by accelerated cooling during the Late Miocene to Early Pliocene (~ 10-4 Ma). These results suggest the presence of a paleo-Yarlung River and/or intensification of the Asian monsoon during the Early to Late Miocene. The Pliocene cooling signal is the youngest reported to date along the IYSZ and likely reflects increased river incision of the Yarlung-Tsangpo driven by accelerated orogen-parallel extension across structures which cross-cut the IYSZ. Robust interpretation of thermochronologic data requires knowledge about the geologic factors and intrinsic properties of the minerals. Appendix D of this dissertation examines intragranular zonation as a source of anomalously young zircon (U-Th)/He ages from leucogranites that intrude Greater Himalayan Sequence rocks at Ronbguk Valley, north of Mt. Everest. Depth profile laser ablation ICP-MS analysis was used to quantify the U-Th concentration profiles of a series of zoned, single, whole zircon grains and to apply a grain specific zonation-dependent age correction. Zircon grains corrected for zonation yield zircon He ages of 15-17 Ma, in agreement with AFT, ZFT and mica ⁴⁰Ar/³⁹Ar ages from the region. This study highlights the importance of characterizing intragranular zonation, especially in complex, zoned zircons that are typical of crustal melts and high-grade metamorphic rocks. Appendix E synthesis the results from Appendices A-C in the context of a global comparison with other ancient and preserved forearc basins. Results from the Xigaze forearc basin are compared to general models for forearc basin formation, subsidence trends, and preservation. The results show similarities between the Xigaze forearc basin and modern forearc basins, such as the Japan forearc off Honshu Island. The mechanisms driving tectonic subsidence are addressed, but remain an area of frontier research in continental dynamics.

Stratigraphic records in Middle Park in north-central Colorado provide evidence for the late Quaternary geomorphic and environmental history of a non-glaciated Southern Rocky Mountain basin. Episodes of geomorphic instability apparent in the stratigraphic record coincide with changes in paleoenvironmental records from above 2750 m in north-central Colorado, suggesting that the western Middle Park landscape was sensitive to environmental changes affecting the region over the last ~14,000 years. Tributaries were incised prior to 14.0 ka, but deposits older than 12.0 ka are rare. Upland erosion and incision followed by rapid aggradation in alluvial settings between 12.0 and 11.0 ka coincide with evidence for regional temperatures at or above present, and is interpreted to signal the onset of Holocene summer-wet precipitation. A widespread soil-stratigraphic marker represents a long period of landscape stability between <11.0 and 6.0 ka in upland and alluvial settings. Pedologic evidence from upland settings indicates the expansion of grass and forest cover to lower elevations that today are characterized by sagebrush steppe, probably during a period of increased summer precipitation relative to present. During the late Holocene, episodes of aggradation in alluvial valleys at 6.0-1.0 ka and 0.6-0.2 ka and soil formation in uplands at 5.0-3.5 ka and 2.5-1.0 ka overlap with evidence for cooling at higher elevations. Incision of valley floors documented at 1.0-0.6 ka and during the last few centuries and episodes of erosion in uplands at 3.5-2.5 ka, after 1.0 ka, and within the last few centuries, are roughly synchronous with evidence for warming. Upland and alluvial stratigraphic records are interpreted to indicate that during cool intervals summer precipitation was diminished, resulting in relative hillslope stability and gradual valley bottom aggradation, while pulses in summer precipitation accompanying warmer episodes caused basin-wide geomorphic instability. The recent increasing frequency of geomorphic instability appears to correspond with an increase in sagebrush steppe at the expense of forest and grass cover, interpreted to represent progressive drying during the late Holocene. It stands to reason that future warming, if accompanied by similar patterns in precipitation, will result in continued erosion on a landscape already at a threshold of geomorphic instability.

Meren field, located offshore Niger Delta, is one of the most prolific oil-producing fields in the Niger Delta. The upper Miocene D-07, D-08 and E-01 oil sands comprise a series of stacked hydrocarbon reservoirs in Block 2 of Meren field. These reservoir sandstones were deposited in offshore to upper shoreface environments. Seven depositional facies were identified in the studied interval, each with distinct lithology, sedimentary structures, trace fossils, and wire-line log character. The dominant lithofacies are (1) locally calcite-cemented highly-bioturbated, fine-grained sandstones, (middle to lower shoreface facies); (2) cross-bedded, fine- to medium-grained well-sorted sandstones (upper shoreface facies); (3) horizontal to sub-horizontal laminated, very-fine- to fine-grained sandstone (delta front facies); (4) massive very-fine- to fine-grained poorly-sorted sandstone (delta front facies); (5) muddy silt- to fine-grained wavy-bedded sandstone (lower shoreface facies); (6) very-fine- to fine-grained sandy mudstone (lower shoreface facies); and (7) massive, silty shales (offshore marine facies). Lithofacies have distinct mean petrophysical properties, although there is overlap in the range of values. The highest quality reservoir deposits are cross-bedded sands that were deposited in high-energy upper shoreface environments. Calcite cements in lower shoreface facies significantly reduce porosity and permeability. Integration of core and wire-line log data allowed porosity and permeability to be empirically determined from bulk density. The derived equation indicated that bulk density values could predict 80% of the variance in core porosity and permeability values. Three parasequence sets were interpreted, including one lower progradational and two upper retrogradational parasequence sets. The progradational parasequence set consists of upward-coarsening delta front to upper shoreface facies, whereas the upward-fining retrogradational parasequence sets are composed of middle to lower shoreface deposits overlain by offshore marine shales. The limited amount of core data and the relatively small area of investigation place serious constraints on stratigraphic interpretations. Two possible sequence stratigraphic interpretations are presented. The first interpretation suggests the deposits comprise a highstand systems tract overlain by a transgressive systems tract. A lowstand systems tract is restricted to an incised valley fill at the southeastern end of the study area. The alternate interpretation suggests the deposits comprise a falling stage systems tract overlain by transgressive systems tract.

Peatlands provide a variety of ecosystem services including carbon sequestration, nutrient cycling and increased biodiversity, and are thus an important Canadian natural resource. Mountain peatlands, including those in the foothill region of the Canadian Rockies are particularly important due to their proximity to headwater streams which supply the Prairie Provinces with water. Yet, distribution of peatlands in the Canadian Rocky Mountains is unknown. There is also a lack of understanding of the form of these peatlands and the processes influencing them. The purpose of this research is to improve our understanding of Canadian mountain peatlands in terms of their abundance, distribution and subsurface form. Specific objectives are to: determine the distribution of beaver impacted wetlands in the study area; quantify the proportion of these which are peatlands; determine the impact beaver have on one hydrological variable, the area of open water and; describe the stratigraphy of peatlands with beaver at their surface. Beaver impacted wetland distribution was assessed through manual analysis of georeferenced aerial photographs. Combining these data with an existing GIS layer provided the basis of a wetland inventory of the region, allowing wetlands to be separately inventoried by physiographic location (Mountain and Foothills) and jurisdiction (Alberta Parks, Municipal Districts, Improvement Districts and First Nations Reserve). Approximately 75% of wetlands are located in the Foothills and Municipal District areas. Beaver impact is evident in 30% of the 529 wetlands inventoried, with the highest number in protected areas. Area of open water on wetlands, as assessed by manual analysis of aerial photographs, indicated that beaver impacted sites have on average approximately ten times more open surface water area than non- beaver impacted sites. In total, 81 wetlands were ground-truthed of which 77% were peat-forming wetlands or peatlands. Ground penetrating radar surveys and soil coring performed at 9 peatlands with beaver activity at their surface showed structural differences from those peatlands for which ecosystem services are described in the literature in that they are stratigraphically complex. Little is known about the factors affecting how this form develops, and this requires further study. The distribution of peatlands in the study area highlights them as important landscape units, and that in order to best manage them, further research is required into the various influences on their hydrological and ecological function.

Part of the Slave Structural Province, the Hope Bay Greenstone Belt is a 82 km long north-striking sequence of supracrustal rocks dominated by mafic volcanic rocks with lesser felsic volcanic and sedimentary rocks. Mapping of two transects in the southern section and two transects in the northern section have contributed to a robust stratigraphic framework the belt. Three recently discovered Archean lode gold deposits in the Hope Bay Greenstone belt have associations with major structures and specific lithologies (Fe-Ti enriched basalts). The Flake Lake and the Clover Transects are in the southern part of the belt and the Wolverine and Doris-Discovery Transects are in the northern part of the belt. This work subdivides the volcanic rocks into distinct suites based upon field, petrologic, geochemical, and geochronologic criteria. Some of the suites are stratigraphically continuous and can be correlated tens of kilometres along strike thereby linking the two parts of the Hope Bay Greenstone Belt. U-Pb geochronology supports work by Hebel (1999) concluded that virtually all the supracrustal rocks in the Hope Bay Greenstone Belt were deposited over at least 53 m.y. (2716-2663 Ma), with the majority of the volcanism occurring after 2700 Ma. A number of basalt groups are identified and include the normal basalt, the LREE-enriched basalt, the Ti-enriched basalt and the Ti-enriched Al-depleted basalt groups. They have chemical signatures that vary in trace elements particularly HFSE and REE’s, and can be easily be distinguished by geochemical screening. The felsic volcanic suites are also divided into three main groups, tholeiitic rhyolite, calc-alkaline dacite and calc-alkaline rhyolite groups. Nd and Hf isotope signatures are consistent with trace element signatures in identifying mafic and felsic volcanic groups, with the tholeiitic rhyolite showing highly variable signature. The Hope Bay Greenstone Belt has been show to have a number of felsic and volcanic cycles. An early construction phase of the belt is made up of primarily mafic volcanics which is followed by felsic volcanism equalled mafic volcanism which lacks basalts enriched in Ti. The geodynamic environment that created the Hope Bay Greenstone Belt can be explained by plume influenced subduction zone.