The Spencer Formation in Yamhill and Washington Counties, Oregon, is exposed in a narrow belt 27 km long, from 1/4 to 3 km wide and with a maximum thickness of about 400 m. The formation is composed entirely of sandstone with interbedded thin layers of mudstone in the uppermost member. The sedimentary structure and paleoecology indicate a shallow marine depositional environment. The upper member of the Spencer Formation contains more quartz, plagioclase, and hornblende than does the lower member, but K-feldspar is less than that of the lower member. Shallower water conditions for the deposition of the upper member are indicated by sedimentary structures and the abundance of pebbly lenses and coaly material. Eighteen species of megafossils collected from the formation indicate that the Spencer Formation is of the Tejon stage (late Eocene of the West Coast).

Inherent characteristics (autogenic behavior) of sedimentary systems are often thought to generate small-scale noise in the stratigraphic records and usually ignored in the stratigraphic interpretation. However, autogenic dynamics can also occur over large temporal and spatial scales and produce sedimentary records that mimic stratigraphic signals presumed to result from changes in external boundary conditions (allogenic forcings) such as tectonics, climate, eustatic change or a combination. As the autogenic fluctuations could impose first-order controls on stratigraphic architecture, it is necessary to search for quantitative methods in order to constrain river intrinsic behaviors and decode them from the complex stratigraphic responses by the scales over which autogenic stratigraphic patterns are most prevalent. The statistical metric we developed based on numerical modeling and physical experiments offers a good prediction on the autogenic time scales and results in a compensation index which can be used as an indicator for fluviodeltaic stratigraphic patterns. The magnitude of autogenic forcings presented in the fluvial successions is associated with the strength of channel-belt clustering and can be quantitatively classified by the compensation index. We utilize this index in conjunction with a serial of 2-D object-based stratigraphic stacking models, high-resolution experimental and field data to (1) quantify how the magnitude of autogenic processes varies with scales (2) understand how autogenic behaviors interact with river discharge and how this allogenic condition affects the stacking patterns of channel bodies (3) explore the mechanism by which surface topography and river kinetics influence the degree of stratigraphic organization in a net-aggradation system / acase@tulane.edu

A liquid chromatographic technique using ultrastable-Y (US-Y) molecular sieve as the stationary phase and n-pentane as the mobile phase has been developed to fractionate and enrich pentacyclic triterpanes from petroleum. The sieve provides a shape-selective window which distinguishes between the various pentacyclic components, thus fractionating them on the basis of molecular shape differences. This sieving technique has been applied to isolate various pentacyclic triterpanes from sedimentary organic matter to enable better analysis of these biomarkers to be carried out.Biodegraded crude oils from three Australian basins were analysed to assess the geochemistry of their rearranged hopanes. Enhanced abundances of 25-norhopanes, 18(alpha)-30-norneohopane and diahopanes relative to the regular hopanes were observed in the most severely biodegraded samples. Geochemical interpretation of these results suggests that the enhanced abundances are due to the greater resistance of rearranged hopanes to biodegradation compared to regular hopanes. These studies also indicate that enhanced relative abundances of 25-norhopanes in these samples is most likely due to selective bacterial demethylation of (alpha beta)-hopane precursors.A branched and cyclic alkane fraction from a higher plant-derived crude oil was subjected to the US-Y chromatography procedure and the fractions eluted from the column were analysed using GC-MS. The compositions of the first two eluted fractions were markedly different from the initial branched and cyclic alkane mixture in that they were enriched in higher plant-derived triterpanes, such as bicadinanes, spirotriterpane and the oleananes and other, previously unreported, C(subscript)29 and C(subscript)30 triterpanes. A comparison of mass spectral data, GC retention and molecular sieve sorption characteristics of these compounds with those of known ++ / triterpanes of known molecular structure was used to suggest structures for the unknown compounds.Isolation of crude oil fractions enriched in pentacyclic alkanes using the sieving procedure enabled lower concentrations of bicadinanes to be detected than was previously possible by applying selective ion detection GC-MS to branched and cyclic alkane fractions. Application of this technique to a higher-plant derived Jurassic crude oil and two Jurassic sediments from the Eromanga Basin, Australia has revealed the presence of bicadinanes. The occurrence of the cis-cis-trans and trans-trans-trans bicadinane biomarkers that have previously only been reported from angiosperms may indicate an early evolution of flowering plant like species in this basin.The molecular sieving technique has also been used to isolate three pentacyclic triterpanes from low rank coals in order to obtain unambiguous structural identification and to determine their geochemical significance. A major hopanoid component isolated from a Victorian brown coal was characterised by single crystal X-ray diffraction and (subscript)13C NMR spectroscopy as 22R 17(alpha),21(beta)(H)-homohopane. This compound was shown to correspond to the later eluting 17(alpha),21(beta)(H)-homohopane and hence, for the first time, confirmed the common practice of assigning the higher retention time peak in gas chromatograms of (alpha beta) homohopanes as the 22R diastereomer. Heating of the isolated 22R (alpha beta)-homohopane on anthracite produced a mixture of the 22S and 22R diastereomers which implied a product-reactant relationship between the two epimers. Furthermore, a C(subscript)29 and a C(subscript)30 triterpane present in the hydrous pyrolysate of a Bremer Basin coal were also isolated using the molecular sieving procedure. 28 Nor-18(alpha)-oleanane was characterised by single crystal X-ray analysis while lupane was ++ / characterised by (subscript)13C NMR spectroscopy and by co-chromatography with an authentic standard on four different GC phase columns. The unusual occurrence of these triterpanes was attributed to the high sulphur content of the coal.Finally, laboratory isomerisation and reduction of an isomeric mixture of oleanenes was carried out to investigate the origin of oleanane (18(beta)-oleanane) and 18(alpha)-oleanane. Laboratory results indicated that oleanane was mainly derived from olean-18-ene, while 18(alpha)-oleanane was derived from 18(alpha)-olean-12-ene. Analysis of oleanene/oleanane abundances in a sedimentary sequence from Indonesia provided results consistent with laboratory evidence showing that 18(alpha)- olean-12-ene, rather than oleanane, is the main sedimentary precursor of 18(alpha)- oleanane.

2D and 3D basin models have been constructed of the southern and central parts of the Vulcan Sub-Basin, which is located in the Timor Sea, north-western Australia. This work was carried out in order to better elucidate the petroleum migration and accumulation histories and exploration potential of the region. The study area extended from the southern limit of the Swan Graben in the south-west to the northern part of the Cartier Trough in the north-east. The results from the basin modelling have been compared with the seafloor bathymetry and physiography, the spatial distributions of hydrocarbon related diagenetic zones (HRDZs) in the region, as well as the distribution of other leakage and seepage indicators. A new method for identifying potential HRDZs using seismic data has also been developed. The 2D/3D modeling results from the Swan Graben indicate that horizontal and downward oil expulsion from the source rocks of the Late Jurassic Lower Vulcan Formation into the upper Plover Formation sandstones was active from the Early Cretaceous to the present day. Oil migration from the Lower Vulcan Formation into the Late Cretaceous Puffin Formation sands in the Puffin Field was simulated via lateral migration along the bottom of an Upper Vulcan Formation seal and by vertical migration above the seal edge. Modelling also indicates that Late Jurassic sequences over the Montara Terrace are thermally immature and did not contribute to the hydrocarbon accumulations in the region. On the other hand, 3D modelling results indicate that the Middle Jurassic Plover Formation in the Montara Terrace became thermally mature after the Pliocene and hence it could have contributed to both the specific hydrocarbon accumulations and the overall hydrocarbon inventory in the area. In the southern Cartier Trough, the Lower Vulcan Formation is typically at a lower thermal maturity than that seen in the Swan Graben, due to a combination of a relatively recent (Pliocene) increased burial and a thinner Lower Vulcan Formation. Here, horizontal and downward oil/gas expulsion from the Lower Vulcan Formation into the Plover Formation sandstone was active from the Late Tertiary to the present day, which is significantly later than the timing of the expulsion in the Swan Graben. In the central Cartier Trough, the areal extent of both generation and expulsion increased as a result of rapid subsidence and deposition from about 5.7 Ma to the present day. This Pliocene loading has resulted in the rapid maturation of the Early to Middle and Late Jurassic source system and expulsion of oil very recently. Oil migration from the Lower Vulcan Formation into the Jabiru structure, via the Plover Formation carrier bed, was simulated in both the 2D and the 3D modelling. In particular, the 3D modelling simulated oil migration into the Jabiru structure, both from the southern Cartier Trough (after the Miocene) and also from the northern Swan Graben (in the Early Cretaceous). Early gas migration, and the attendant formation of a gas cap, was also simulated. Importantly, this result provides a potential alternative interpretation for the formation of at least some of the residual zones in the Timor Sea, as well as in other areas. Traditionally, most of the residual zones within the Timor Sea have been attributed to fault seal reactivation and failure. However, the simulated early gas cap in the Jabiru structure has formed as a result of gas exsolution as the migrating hydrocarbons entered the Jabiru trap (and its shallow flanks), which was then only located a few hundred metres below the surface. The rapidly decreasing pressure allowed the gas to form a separate phase, with the result that in the Early Cretaceous, in the 3D model, the Jabiru trap was composed of a relatively large gas cap with a thinner (“black oil”) oil leg. Progressive burial through the Tertiary, and the attendant increase in pressure, resulted in the gas going back into solution. The associated decrease in the bulk volume of the hydrocarbon accumulation produced a “residual” oil zone at the base of the column, purely through a change in phase, rather than through loss of hydrocarbons from fault seal failure, for example. The processes outlined in this scenario would be essentially indistinguishable from those produced by fault seal failure when assessing traps using fluid history tools such as GOI. Such a process could be critically important in the case of shallow, low-relief traps, where only the exsolved gas could be trapped, with the “black oil” component displaced below the spill of the trap. Small, sub-commercial gas fields would thus be located around the periphery of the source depocentres - though these would be the result of an early, rather than late, gas charge. Small black oil accumulations could be developed inboard from such gas fields. A new method to extract HRDZs from 3D seismic data has predicted the location of new HRDZs in the northern Vulcan Sub-basin. Further investigation is needed to confirm/refine the method but it has the potential to significantly aid HRDZ mapping (and seal assessment and hydrocarbon migration studies). A workflow for future studies is proposed which includes inputs from basin modelling, leakage and seepage mapping, and fault seal and fault reactivation studies. Implementation of this workflow should ultimately allow a more reliable estimation of GOR prior to drilling. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1277632 / Thesis(M.Sc.)-- Australian School of Petroleum, 2007.

Thesis (Honors)--College of William and Mary, 2009. / Includes bibliographical references (leaves 59-61). Also available via the World Wide Web.

Thesis (doctoral)--Université de Rennes I, 2003. / Errata sheets inserted. Includes bibliographical references (p. 239-253, 266-270). Also available on the Internet.

The South China Craton comprises the Yangtze Block in the northwest and Cathaysia Block in the southeast. Located in the southeastern Yangtze Block, the Jiangnan Orogen formed through the amalgamation between the Yangtze and Cathaysia Blocks. The Yangtze Block has sporadically exposed Archean rocks in the north, Paleoproterozoic to Mesoproterozoic volcano-sedimentary sequences in the southwest and widespread Neoproterozoic sedimentary sequences accompanied by syn-sedimentary igneous rocks on the western and southeastern margins. The late Paleoproterozoic to early Mesoproterozoic Dongchuan, Dahongshan and Hekou groups in the southwestern Yangtze Block formed in a series of fault-controlled, rift-related basins associated with the fragmentation of the supercontinent Columbia. These sedimentary sequences were deposited between 1742 and 1503 Ma, and recorded continuous deposition from alluvial fan and fluvial sedimentation during the initial rifting to deep marine sedimentation in a passive margin setting. Sedimentation during initial rifting received felsic detritus mainly from adjacent continents, whereas sedimentation in a passive margin basin received detritus from felsic to intermediate rocks of the Yangtze Block. Paleoproterozoic to Mesoproterozoic rift basins in the southwestern Yangtze Block are remarkably similar to those of north Australia and northwestern Laurentia in their lower part (1742-1600 Ma), but significantly different after ca. 1600 Ma. The southwestern Yangtze Block was likely connected with the north Australia and northwestern Laurentia in Columbia but drifted away from these continents after ca. 1600 Ma. Traditionally thought Mesoproterozoic sedimentary sequences in the southeastern Yangtze Block are now confirmed to be Neoproterozoic in age and include the 835-830 Ma Sibao, Fanjingshan and Lengjiaxi groups, and 831-815 Ma Shuangqiaoshan and Xikou groups. These sequences are unconformably overlain by the ~810-730 Ma Danzhou, Xiajiang, Banxi, Heshangzheng, Luokedong and Likou groups. The regional unconformity likely marked the amalgamation between the Yangtze and Cathaysia Blocks and thus occurred at ~815-810 Ma. The lower sequences (835-815 Ma) received dominant Neoproterozoic (~980-820) felsic to intermediate materials in an active tectonic setting related to continental arc and orogenic collision, whereas the upper sequences represent sedimentation in an extensional setting with input of dominant Neoproterozoic granitic to dioritic materials (~740-900 Ma). The upper parts of the Shuangqiaoshan and Xikou groups, uncomfortably underlain by lower units, are molasse-type assemblages with additional input of pre-Neoproterozoic detritus, representing accumulation of sediments in a retro-arc foreland basin associated with the formation of the Jiangnan Orogen. Stratigraphic correlation, similarly low-δ18O and tectonic affinity of igneous rocks from different continents suggest that the Yangtze Block should be placed in the periphery of Rodinia probably adjacent to northern India. Paleoproterozoic (~2480 Ma and ~2000 Ma) and Early Neoproterozoic (711-997 Ma) were the most important periods of crustal and magmatic events of the southeastern Yangtze Block, but there is a lack of significant Grenvillian magmatism. Early Neoproterozoic magmatism highlights the contribution from both juvenile materials and pre-existing old crust, whereas ~2480 Ma and ~2000 Ma events are marked by reworking of pre-existing continental crust. Magmatism at 1600-1900 Ma was dominated by reworking of pre-existing crust, whereas the 1400-1600 Ma magmatic event recorded some addition of juvenile materials. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

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This work describes a new taxonomy for elastic, sedimentary porous media. The taxonomy is synthesized for the investigation and characterization of ground-water flow from accumulating developments in the genetic analysis of elastic, sedimentary depositional structures. Genetic analysis recognizes spatial associations of elastic, sedimentary structures imposed during genesis. The taxonomy is a nested hierarchy of discrete elastic, sedimentary structures distinguished by the bounding surfaces created during their emplacement and rearrangement. The investigation and characterization of a specific ground-water flow system in elastic, sedimentary porous media can be improved by imposing a structural context on lithologie observations, geophysical measurements, head measurements, and hydraulic conductivity estimates. Globally-valid and transferable descriptions of structures in the taxonomy from modern exposures, outcrops, and densely sampled subsurface systems are modified to fit site-specific geologic observations and measurements. A specific procedure is developed for applying the taxonomy in the investigation and analysis of ground-water flow. The procedure quantitatively measures the hydraulic validity of alternative geologic interpretations of site-specific data under the taxonomy. The application of the taxonomy and procedure to a typical set of data types, densities, and quality is illustrated with data from a site of ground-water contamination investigation.

No description available.