Taylorsville Basin Research Articles

Bacteria work together to survive Earth’s depths

Thousands of feet below the Earth’s surface seems an unlikely cradle for life. Indeed, for a long time, scientists wondered if any life could survive in such a hostile, pitch black, oxygen-poor environment. Working in the depths of a gold mine, Maggie Lau ( Left ) and Rachel L. Harris ( Right ) filter water to capture microbial cells onto a filter membrane. Image courtesy of Rachel L. Harris (Princeton University, Princeton). But about two decades ago, researchers found the first substantive evidence of organisms living deep underground. A Department of Energy drilling project had recovered rocks from more than a mile below the Earth’s surface in the Taylorsville Basin in Virginia, and scientists were surprised to find that these rocks harbored bacteria. More recently, researchers went looking for microscopic worms in deep mines, and discovered a variety of eukaryotic organisms living at these depths (1, 2). Most of these eukaryotes survive by eating deep-living bacteria. But there’s still a lot we don’t know about how the bacteria themselves survive in an environment without sunlight or plentiful oxygen for energy. Recent work, based on samples painstakingly retrieved from deep gold mines, appears to provide a crucial clue: the bacteria work together in intricate networks, cooperating to survive. “We have long understood that life exists in the deep subsurface, but we don’t actually know what they’re doing in that environment,” says Maggie Lau, a geomicrobiologist at Princeton University and the study’s first author. Lau and her colleagues identified and analyzed the metabolic networks used by deep-living bacterial communities. By capturing the “metabolic landscape” of these underground environments, the authors showed that the bacteria use a wider range of energy sources than expected, and work together to survive (3). Studying these kinds of metabolic landscapes will be crucial for understanding …

Redescription and phylogenetic relationships of Doswellia kaltenbachi (Diapsida: Archosauriformes) from the Upper Triassic of Virginia

ABSTRACT A detailed redescription of the Late Triassic archosauromorph reptile Doswellia kaltenbachi Weems, 1980 from the Poor Farm Member of the Falling Creek Formation in the Taylorsville basin (Newark Supergroup) in Virginia is presented based upon additional preparation of the holotype. The euryapsid skull has a distinctive occiput with a prominent supraoccipital process that is flanked by posterior “horn-like” projections of the squamosals. Postfrontals, tabulars, and postparietals are absent. Plesiomorphic features of the palate and braincase include a plate-like horizontal parabasisphenoid, a pair of foramina for the internal carotid arteries on the ventral surface of the basisphenoid, and two fields of teeth on the palatal surface of the pterygoid. A sharp angle along the cervical and anterior dorsal ribs clearly separates the dorsal and lateral sides of the neck and anterior thoracic region. The posterior thoracic region has shorter ribs that project laterally with only a slight curvature. The ilium has a laterally deflected blade with numerous deep grooves along its distal edge. The laterally extensive set of osteoderms includes a nuchal element that is composed of several interlocking osteoderms that lack the arrangement in distinct transverse rows that characterizes the remainder of the osteoderms. A phylogenetic analysis of basal archosauriforms incorporates new data of Doswellia and the taxa Turfanosuchus, Yonghesuchus, and Qianosuchus that have not previously been combined in a single study. Results include a sister-group relationship between Doswellia and proterochampsids, placement of Qianosuchus as a crurotarsan archosaur, and Yonghesuchus and Turfanosuchus as successive sister taxa to Archosauria.

Paleofluid-flow circulation within a Triassic rift basin: Evidence from oil inclusions and thermal histories

The migration of subsurface fluid flow within continental rift basins has been increasingly recognized to significantly affect the thermal history of sediments and petroleum information. To gain insight into these paleofluid flow effects, the thermal history of the Taylorsville basin in Virginia was reconstructed from fluid-inclusion studies, apatite fission-track data, and vitrinite reflectance data. Models of thermal history indicate that the basin was buried to the thermal maximum at 200 Ma; a cooling event followed during which the eastern side of the basin cooled earlier and faster than the western side, suggesting that there was a differential uplift and topographically driven fluid flow. This hypothesis is supported by analyses of secondary oil and aqueous inclusions trapped in calcite and quartz veins during the uplift stage. Gas chromatograms of inclusion oils exhibit variable but extensive depletion of light molecular-weight hydrocarbons. The relative abundance of n-alkanes, petrographic observations, and the geological data indicate that the alteration process on these inclusion oils was probably neither phase separation nor biodegradation, but water washing. Water:oil ratios necessary to produce the observed alteration are much greater than 10,000:1. These exceedingly high ratios are consistent with the migration of inclusion oils along with fluid flow during themore » early stages of basin evolution. The results provide significant evidence about the role of a subsurface flow system in modifying the temperature structure of the basin and the composition of petroleum generated within the basin.« less

Observations pertaining to the origin and ecology of microorganisms recovered from the deep subsurface of Taylorsville Basin, Virginia

To understand the conditions under which microorganisms exist in deep hydrocarbon reservoirs, sidewall cores were collected from a natural gas‐bearing formation, 2800 m below the surface in Taylorsville Basin, Virginia. Data from chemical and microbial tracers and controls indicate that the interiors of some sidewall cores contained microorganisms indigenous to the rock formation. The cultured microorganisms were composed primarily of saline‐tolerant, thermophilic fermenting, Fe(III)‐reducing, and sulfate‐reducing bacteria (1 to 104 cells/g). The physiological capabilities of the cultured microorganisms are compatible with the temperature (76°C), pressure (32 MPa), and salinity (≈0.8 wt.% NaCl equivalent) in the sampled interval. The petrological data indicated that the strata contain intercrystalline pores of micrometer size, that occur between late diagenetic cement in siltstone and within cross‐cutting, mineralized fractures in shale. These pores made up only 0.04% of the rock volume, were mostly gas‐filled, and were interconnected by pore throats with diameters <0.04 μm. Because the pore throats are smaller than known bacteria, the cultured microorganisms were probably trapped within the larger pores containing alkaline, brackish, formation water. The total phospholipid fatty acid concentration of the rock samples yielded a cellular concentration equivalent to 4 x 105 cells/g, much greater than had been determined by enumeration of the cultured bacteria. This may have resulted from either inhibition of dephosphorolation reactions within pores filled with reduced gases, such as methane, or the inability to culture >0.1% of the viable bacteria. The recovery of living bacteria from such an austere environment represents one of the most remarkable examples of microbial survival yet reported.

Hydrogeologic Constraint on the origin of deep subsurface microorganisms within a Triassic Basin

The thermal history of the Taylorsville basin indicates that the thermophilic anaerobic bacteria extracted from Triassic strata at 2800 m below the land surface within the basin probably migrated to their current location. In order to ascertain the most probable scenario for microbial transport, a two‐dimensional transient fluid flow and heat transport model of the Taylorsville basin was developed using the finite element method. The numerical model was constrained by tectonic and thermal histories of the basin, coupled with the permeability and porosity data extracted from core samples. The model demonstrates that a topographically driven groundwater flow system, caused by the tectonic uplift and erosion during the Jurassic, can explain the observed differential cooling of the basin. The computed groundwater flow rates during this period were on the order of 1 to 100 mm/yr. Combined with the cooling history of the microbially sampled strata, such rates provided a possible mechanism for the introduction of ancient surface or subsurface microorganisms to the deep subsurface. This tectogenetic mechanism may explain the origins of deep subsurface microorganisms for other regions of the Earth.

A tectogenetic origin for the deep subsurface microorganisms of Taylorsville Basin: thermal and fluid flow model constraints

Thermophilic anaerobic bacteria extracted from Triassic, 230 million years old (Ma), sandstone and shale at 2800 m below the land surface in the Taylorsville Basin, Virginia, appear to be indigenous to the rock strata. The observed maximum growth temperatures of these bacteria, 65–75°C, are compatible with the current formation temperatures. Paleogeothermometers, however, indicate that the strata were exposed to temperatures of 160–200°C at 200 million years ago. This implies that the bacteria migrated to their current depth after this thermal pulse. A 2D paleofluid flow and heat transport model indicates that during uplift and erosion in the Jurassic, 200–140 Ma, topography drove groundwater deep into the subsurface at a rate of 1–100 mm/year. The estimated minimum time required for water to move from the surface to the microbially sampled horizons during this time interval ranges from 1 to 20 million years. The time required to migrate from a depth compatible with the growth range of microorganisms, approximately 1.3 km, to the microbially sampled horizons would be even less. The present-day groundwater flow rates, however, are 10–100 times less than those during the Jurassic and the minimum time required for water to reach the microbially sampled zones from the surface is 50–180 million years. Colonization of the deep subsurface, therefore, probably occurred during the basin's last major tectonic event in the Jurassic rather than today. For many regions of the earth's crust, the age of deep subsurface microbial communities may be equal to that of the last tectonic upheaval.

Constraints on the thermal history of Taylorsville Basin, Virginia, U.S.A., from fluid-inclusion and fission-track analyses: implications for subsurface geomicrobiology experiments

Microbial populations have been found at the depth of 2621–2804 m in a borehole near the center of Triassic Taylorsville Basin, Virginia. To constrain possible scenarios for long-term survival in or introduction of these microbial populations to the deep subsurface, we attempted to refine models of thermal and burial history of the basin by analyzing aqueous and gaseous fluid inclusions in calcite/quartz veins or cements in cuttings from the same borehole. These results are complemented by fission-track data from the adjacent boreholes. Homogenization temperatures of secondary aqueous fluid inclusions range from 120° to 210°C between 2027- and 3069-m depth, with highest temperatures in the deepest samples. The salinities of these aqueous inclusions range from 0 to ∼ 4.3 eq wt% NaCl. Four samples from the depth between 2413 and 2931 m contain both two-phase aqueous and one-phase methane-rich inclusions in healed microcracks. The relative CH 4 and CO 2 contents of these gaseous inclusions was estimated by microthermometry and laser Raman spectroscopy. If both types of inclusions in sample 2931 m were trapped simultaneously, the density of the methane-rich inclusions calculated from the Peng-Robinson equation of state implies an entrapment pressure of 360 ± 20 bar at the homogenization temperature (162.5 ± 12.5°C) of the aqueous inclusions. This pressure falls between the hydrostatic and lithostatic pressures at the present depth 2931 m of burial. If we assume that the pressure regime was hydrostatic at the time of trapping, then the inclusions were trapped at 3.6 km in a thermal gradient of ∼ 40°C/km. The high temperatures recorded by the secondary aqueous inclusions are consistent with the pervasive resetting of zircon and apatite fission-track dates. In order to fit the fission-track length distributions of the apatite data, however, a cooling rate of 1–2°C/Ma following the thermal maximum is required. To match the integrated dates, the thermal maximum would have occurred at ∼ 200 Ma. The timing of the maximum temperature is consistent with rapid burial of the Taylorsville Basin to twice its present-day depth and thermal re-equilibration with a 40°C/km geothermal gradient, followed by slow exhumation. The results may imply that the microorganisms did not survive in situ, but were transported from the cooler portions of the basin sometime after maximum burial and heating.

Diagenesis of Triassic Sandstones in the Taylorsville Basin of Virginia: ABSTRACT

Diagenesis of Triassic Sandstones in the Taylorsville Basin of Virginia: ABSTRACT

An Environmentally Correct Drilling Effort: Texaco's Taylorsville Basin Exploration Program

Through the early and mid-1980s, Texaco conducted geophysical, geochemical, and stratigraphic test programs along the Mid-Atlantic Coast of the United States. A drilling program was ultimately focused at the Triassic sediments of the Taylorsville basin straddling the Virginia-Maryland border. Three wildcat wells were drilled between 1989 and 1992. All were dry holes. Although the prospect was a geological disappointment to Texaco, the environmental concern and precaution exhibited throughout the effort stand as testament to a major oil company's ability to conduct operations in an environmentally prudent manner. Although the operations involved only inland drill sites, all locations were extremely close to the Chesapeake Bay, one of the world's most fragile esturial ecosystems. Protective techniques employed included the use of closed freshwater mud systems, protective levee and drainage containment, comprehensive backup and emergency plans, and heightened safety awareness. Texaco also embraced an open policy regarding public education and input. By means of town meetings, public hearings, and thousands of rig visits, Texaco believes it has enhanced the public perception and enthusiasm for exploratory drilling in the Tidewater region.

Oil and Gas Developments in Atlantic Coastal Plain and Outer Continental Shelf in 1989

Oil and gas exploration on the Atlantic coastal plain has been focused on the buried Mesozoic rift basins. In 1989, Texaco drilled an unsuccessful new-field wildcat in the Taylorsville basin in Virginia. Also in 1989, 5 wells were drilled into rift basins and coastal plain sediments overlying the basins in Georgia. There has been no exploration drilling on the Atlantic outer continental shelf (OCS) since the completion of Shell's deepwater drilling program in 1983-1984. Since then, geophysical activity has continued at a low level. There is no oil or gas production from the Atlantic OCS or Atlantic coastal plain outside the state of Florida.

Buried rift basin underlying coastal plain sediments, central Delmarva Peninsula, Maryland

A recently obtained seismic reflection profile provides the first evidence of a buried rift-basin structure underlying the eastern shore of Maryland. This basin, tentatively named the Queen Anne basin, is buried beneath about 1020 m of plain sediments. The eastern margin of the basin was traversed by the seismic line and appears to be the ramping side of a half-graben structure. It is offset by high-angle, antithetic faults that step the crystalline basement surface down to the west. The border fault system is believed to occur on the western margin of the structure and may coincide with a prominent northeast-trending gravity gradient. Rocks filling the rift basin appear to be at least 1250 m thick. The Queen Anne basin may be part of a buried eastern belt of rift basins that follows the generally arcuate trend of the Appalachian orogen before emerging in Virginia as the Taylorsville and Richmond basins.

Depositional and Structural Histories of Richmond and Taylorsville Triassic Rift Basins: ABSTRACT

The Richmond and Taylorsville basins of Virginia display similar structural and sedimentological histories, which differ somewhat from those of other eastern North American rift basins. Both basins formed during the middle Carnian in response to the initial opening of the North Atlantic Ocean. Both are westward tilted half grabens whose border faults share a reactivated Paleozoic basement thrust (the Hylas zone). A dipmeter log from the Bailey 1 well (Richmond basin) shows that bedding dips toward the border fault and increases with depth. These relationships are interpreted to reflect syndepositional rotation and tilting of the basin above a listric normal fault. Unlike the red beds typical of other eastern North American rift basins, sediments of the Richmond and Taylorsville basins are mostly unoxidized gray sandstones and siltstones. The sediments of both basins can be divided into three facies associations. The lowest is a poorly sorted, coarse-grained, lithic arkose rapidly deposited in alluvial fans and braided streams. This was succeeded by sand, silt, and mud of a lower End_Page 1449------------------------------ gradient, fluvial-paludal setting. Organic-rich black shales accumulated in lakes (oxbows?) and overbank deposits. An influx of cross-bedded fluvial sands, possibly triggered by renewed border faulting on the west, characterizes the final stage of basin fill. These sediments represent fan-delta systems that prograded northeastward across the lacustrine-paludal lowlands. End_of_Article - Last_Page 1450------------

Structural Styles and Tectonic Implications of Richmond-Taylorsville Rift System, Eastern Virginia: ABSTRACT

Recent drilling and seismic surveys in the Richmond basin have revealed unexpected results. Alternating episodes of extension and compression have created overprints of structural styles, and generated syndepositional unconformities as sediments were uplifted and rotated. Eroded Triassic sediments from structural highs were redeposited in adjacent synclinal or fault-controlled lows. In addition, lithologic correlation has revealed the existence of large deltaic complexes prograding across the basins, followed by Mississippi-size meander-belt channel deposits in the subsurface. The early lacustrine-deltaic deposits (Vinita beds, etc) appear to have been deposited in a basin much larger than the apparent outcrop limits of the Richmond or Taylorsville basins. As much as 3,000 ft of these deposits accumulated prior to a compressional event that folded them into enormous anticlines and synclines, as Paleozoic thrust sheets were reactivated and sub-Triassic buried hills grew in height, raising the overlying Triassic sediments by as much as 2,000 ft over a distance of less than 2 mi. End_Page 1434------------------------------ The synclines contain a nearly continuous sedimentary sequence, whereas the anticlines have the uppermost Otterdale Sandstone facies as a blanket deposit over their truncated tips and steeply dipping Vinita beds below the unconformity on their flanks. Extensional events followed the main phase of folding and pulled the limbs of the anticlines apart, causing normal listric faults to form and blocks of Vinita beds to separate into North Sea-type fault-block structure. Based on maturation and porosity trends with depth, at least 7,000 ft of overburden have apparently been removed from the basins. Either the structural style changed dramatically from listric faults to horst and graben mechanics, thereby dropping the Richmond-Taylorsville sequences below the present erosional level, or an enormous gravity slide from the east covered the basins, and erosion has created windows through this detached Paleozoic thrust sheet into a much larger Triassic rift system below it. End_of_Article - Last_Page 1435------------

Organic Geochemical Investigations of Eastern U.S. Early Mesozoic Basins: ABSTRACT

Shales rich in organic matter and coalified plant fragments (phytoclasts) in the early Mesozoic basins of the Newark Supergroup of the eastern United States are the topic of a current multidisciplinary study to understand their burial history, their role in ore-forming processes, and their hydrocarbon potential. Samples from the Hartford, Newark, Culpeper, Richmond, Taylorsville, and Deep River basins were analyzed using elemental analysis, nuclear magnetic resonance spectroscopy (NMR), Rock-Eval pyrolysis, stable isotope mass spectrometry, pyrolysis-gas chromatography, and gas chromatography-mass spectrometry. The composition of the preserved organic matter in these samples is highly variable. Most sedimentary rocks of Triassic to Jurassic age in the Hartford, Newark, Culpeper, Richmond, and Deep River basins are in a catagenetic stage of thermal alteration. Samples from the Lower Jurassic Towaco Formation of the Newark basin are the least thermally altered samples analyzed and are apparently at a late diagenetic stage. Most of the older Triassic samples and a few of the latest Triassic to Jurassic samples, however, are highly thermally altered. Phytoclasts from the Lower Jurassic Feltville and Portland Formations, from the Newark and Hartford basins, respectively, are essentially aromatic; however, phenolic groups were observed in the NMR spectra. The initial organic geochemical results imply that the organic matter basically exists in two populations, one with a low to medium rank or level of maturation and the other representing a much higher maturation level. No gradual change in maturation from one rock unit to the next was observed for the samples analyzed, and the distribution of maturities apparently is neither stratigraphically nor temporally controlled. The presence of phenolic groups in the phytoclasts from the Feltville and Portland Formations suggests that carbonization rather than coalification processes may have occurred. End_of_Article - Last_Page 1439------------

Late Triassic palynofloras of North America and their European correlatives

Upper Triassic continental strata in the United States contain rare horizons which yield pollen assemblages. The Dockum Group and Chinle Formation of the American Southwest, as well as certain rock units within the Deep River, Richmond, and Taylorsville Basins of the Newark Group, contain palynomorphs which exhibit stratigraphically restricted ranges in Europe. The presence of Vallasporites ignacii, Camerosporites secatus and Ovalipollis ovalis in the Dockum Group, Chinle Formation, Cumnock Formation of the Deep River Basin, Vinita Formation of the Richmond Basin, and unnamed units in the Taylorsville Basin suggest that all these units are approximately contemporaneous. The occurrence of these and other stratigraphically diagnostic pollen taxa, particularly Patinasporites densus, further indicates a Middle to Late Karnian age for these units. The palynostratigraphy also implies that the Pekin Formation of the Deep River Basin is slightly older than the above mentioned units.