ABSTRACT The structure and stratigraphy of the southeastern San Joaquin basin were reviewed for evidence that would document the impact on the basin of Miocene rotation of the adjacent Tehachapi and San Emigdio Mountains. Outcrops of basement rocks and volcanic intervals at the southeast margin of the basin contain paleomagnetic data indicating up to 59 degrees of clockwise rotation. The study used cross sections and maps of oil fields published by the California Division of Oil, Gas and Geothermal Resources. Information extracted included fault age and orientation, and stratigraphic data including gross unit thickness and net sand thickness. The geologic studies of the oil fields contain an abundance of evidence indicating Miocene extension. South of the Kern River, several fields contain numerous faults of early to middle Miocene age that generally fall on NW-SE or NE-SW trends. Fault offsets indicate a large amount of extension and correspond to the down-dropping of the floor of the Tejon embayment and break-up and collapse of the Edison high. Faults of similar age, present in fields north of the Kern River, have a slightly different NNW-SSE strike. Offsets on this latter set of faults are relatively minor and contributed in forming a wide shelf region. Sediments deposited during the middle and late Miocene reflect different styles of structural extension. South of the Kern River, the depositional gradient was very steep, and sand bodies representing deltaic, shallow-marine and deep marine environments are very localized in extent. North of the Kern River, sands deposited on the wide shelf are laterally extensive and represent deltaic and shallow-marine environments deposited at the terminus of a river system. The structural and depositional styles are similar between the Edison high and Tejon embayment area, indicating that the same structural events were responsible. The structural evidence is consistent with the rotation model of Goodman and Malin (1992) . However, if the Edison high block has rotated, then additional faults may be necessary to accommodate slippage against the adjacent Maricopa sub-basin block. The faulting style north of the Kern River is not consistent with rotation; thus rotation is likely limited to south of the Bakersfield arch.

Abstract The Upper Cretaceous (Cenomanian) Doe Creek Member, encased in the predominantly marine mudstones of the Kaskapau Formation in northwest Alberta, comprises a series of retrogradationally stacked northeast-southwest trending shoreline deposits. An integrated ichnological and sedimentological analysis of these shorelines reveals a complex depositional relationship between deltaic and open-marine shoreface successions. The shoreline trends in the Doe Creek Member display substantial variability in thickness, sedimentology, and ichnological character along depositional strike stemming from proximity to deltaic point sources. The Doe Creek Member exhibits excellent core control in the subsurface, allowing detailed facies analysis of these multifaceted shoreline deposits. The integration of ichnological and sedimentological analysis yields eleven distinct facies in the Doe Creek Member. The facies represent a variety of depositional environments, including fully marine offshore to shoreface deposits and deltaic deposits (e.g., prodelta, delta front, distributary channels and distributary mouth bars). These facies can be divided into two facies associations, based on recurring vertical successions of regressive delta deposits and open-marine shoreface deposits. The deltaic shorelines consistently develop thicker delta front sandstone packages, fed by associated distributary channels. Penecontemporaneous open marine shoreface sandstones, deposited laterally adjacent to the delta fronts, are typically much thinner and display significantly higher bioturbation intensities, resulting in a lower quality reservoir. This dichotomy of reservoir potential and quality has significant implication for hydrocarbon exploration and exploitation. Unfortunately, the deltaic and open-marine shoreface successions appear almost indistinguishable on gamma-ray well log signatures; this renders well-log cross-sections meaningless in terms of understanding the Doe Creek depositional system. In contrast, detailed core-based cross-sections reveal the complex facies architecture of the coeval deltaic and non-deltaic successions. The facies successions and facies architecture of the ancient shorelines of the Doe Creek Member highlight the inherent complexities induced by deltaic influences on a given coastal environment. Deltaic and open-marine shoreface successions are merely the end-members of a spectrum of coastal regimes in which there exist degrees of deltaic influence. Within each regressive shoreline trend, it can be shown that the degree of deltaic character is determined by the lateral proximity to a riverine point source. Therefore it is possible, based on integrated ichnological and sedimentological facies analysis, to locate riverine point sources on a given shoreline trend in the subsurface, which could provide significant economic returns.

Abstract Facies distribution in the late Paleozoic of west Texas indicates that paleolatitude and paleogeography strongly influenced carbonate sedimentation. Placing regional facies maps into their late Paleozoic latitudes and plate orientations can assist in explaining and predicting basin sedimentation patterns. Paleogeographic reconstructions indicate that west Texas was very near the equator throughout the late Paleozoic. This produced a tropical climate that was ideal for widespread carbonate deposition. The response of Paleozoic sedimentation to prevailing winds would have been similar to that presently observed in the low latitudes. Carbonate sedimentation during the Pennsylvanian and Permian responded to these trade winds in a similar fashion as observed in the modern tropics near the equator. The PALEOMAP and TERRAMOBILIS softwares were used to construct plate reconstructions and paleogeographic maps. These maps indicate that during the late Paleozoic North America was rotated approximately 43° northeast from its present setting. Shelf edges in the Delaware and Midland basins presently oriented 0 to 15° were in fact oriented 40 to 60° northeast during the late Paleozoic. Thin coals on the Eastern shelf indicate west Texas was located in a humid tropical climate during the Pennsylvanian. Later, during the Permian, extensive evaporites indicate this area had moved into a more arid tropical climate. This change occurred as the North American plate migrated northward at the end of the Paleozoic. The past orientation of the carbonate shelves must be determined and combined with the direction of prevailing winds to better understand facies distribution. It is not only important to know the direction of prevailing winds, but also which portion of the shelf would have been in a windward location. The location and actual orientation of carbonate shelves are important when considering where the regional prevailing winds would have struck the platform edges during sedimentation. Understanding basin orientation and prevailing wind direction enables the prediction of the distribution of carbonate grain types and carbonate sand-body geometry and location.

ABSTRACT This paper organizes the member lithic unit nomenclature for the San Joaquin basin of California according to “Sequence Stratigraphy” terminology and philosophy of Vail et al (1977)(See Figure 1). Member units are organized by sequences (See Figure 2) that contain a low-stand system and often, a transgressive/high-stand system. The systems respond to relative eustatic sea level changes. Vail et al (1977) deal with unconformities in the sense that they reflect only erosional events and emphasize the unconformity created during relative sea level drops. This paper pays equal attention to both a transgressive sea level change and a relative sea level drop. An updated stratigraphic chart shows sand and shale units which are organized by genetic categories relative to sequences and systems tied into a chronological framework based on California benthic foram stages. Twelve complete sequences are defined. Systems are filled with their specific depositional units. The text provides references for most of the lithic units described. Rock names are identified chronologically and then spatially by working from the Stockton arch fault in the north (See Figure 3), to the south end of the San Joaquin basin. Six diagrammatic cross sections are included to aid in illustrating the geologic relationships.

ABSTRACT The southern San Joaquin Valley has been the site of extensive oil production from the late 1800s to the present. Within the past decade, the disposal of waste fluids associated with exploration, production, storage, and transportation of petroleum has become a concern with regard to ground-water quality. Portions of the San Joaquin Valley, particularly the Buena Vista Valley area, contain ground water with naturally occurring high salinity and total dissolved solids (TDS). These waters have been extracted during oil production, and used for water flood and steam injection operations, further elevating the concentration of salts and other compounds. The recent passage of several environmental laws in California has required disposal of these concentrated fluids at licensed disposal sites. These sites require specific siting criteria, engineering and hydrogeologic evaluation, fluid containment, and long-term unsaturated zone and ground-water monitoring. Disposal facilities operating prior to the implementation of the new criteria may also require hydrogeologic characterization in compliance with state regulations. This paper will provide an overview of past practices, natural hydrogeologic conditions, current regulatory context, and water quality issues at several oil field disposal facilities in the southern San Joaquin Valley.

ABSTRACT The depositional environments and reservoir characteristics of the upper Miocene Etchegoin and Chanac formations in Kern Front oil field, eastern San Joaquin basin, California, were interpreted in cores from three wells. Sedimentary facies were correlated to the log responses and then mapped throughout the reservoirs. The Etchegoin Formation is a shallow-marine unit consisting of a basal transgressive and overlying deltaic units. Facies include shoreface, river-mouth bar, prodelta, paralic, and marine and distributary channel deposits. The shoreface deposits trend north-south, and are interbedded with, and overlain by, bioturbated marine units. They are gradational upward into river-mouth bars and marine channels, and are incised locally by distributary channels. The Chanac Formation underlies the Etchegoin Formation and contains meandering stream sequences deposited on a low-relief, mud-rich coastal plain. West-trending channels are recognized in the Chanac Formation. Log-derived data, combined with core porosity and permeability measurements, indicate that the upper Miocene reservoir sandstones have an average porosity 36.5% and average permeability 2,200 md. The Etchegoin sandstones are poorly indurated, arkosic arenites and wackes composed of subangular, medium- to coarse-grained, poorly-sorted detritus. Detrital modes for the sandstones are Q33 F47 L20 and Qm38 P48 K14. Authigenic minerals are rare and include calcite, illite, and Ca-zeolite. The best reservoir sandstones in the field are the Etchegoin deltaic shoreface and channel facies and the Chanac channel facies. The two factors controlling reservoir quality are grain size and sorting. The proportion of detrital matrix ranges from 11 to 12% in the better reservoir facies to 22 to 45% in the poorer reservoirs; the proportion of the coarsest-grained fraction (sand/gravel) ranges from 54% in the poorer reservoirs to 83% in the better reservoir facies.

ABSTRACT During the upper Miocene the southern San Joaquin Valley underwent rapid structural changes. Localized uplift shed coarse-grained quartz-rich sands into the subsiding Maricopa depocenter, in the form of deep marine turbidites. These upper Miocene turbidites in the southern portion of the San Joaquin basin are collectively referred to as the “Stevens” sands. First encountered in a well drilled in 1936, the Stevens turbidite sands have become a major oil exploration target. A schematic model for the sand-rich Stevens turbidite deposition is used to examine four producing fields within the Maricopa depocenter. Examples of sand-rich turbidite morphology, seismic signatures, depositional styles, and lateral migration of channel-lobe systems will be presented to demonstrate the effect of upper Miocene structural growth upon Stevens deposition within the Maricopa depocenter.