Geology topics

J.J. Kolak

Publications and source records attributed to J.J. Kolak.

6 recordsLinked to original sources

USGS2007

An evaluation of petrogenic hydrocarbons in northern Gulf of Alaska continental shelf sediments - The role of coastal oil seep inputs

We compared hydrocarbons in water, suspended particulate matter (SPM), and riparian sediment collected from coastal watersheds along the Yakataga foreland with corresponding hydrocarbons in Gulf of Alaska benthic sediments. This comparison allows an evaluation of hydrocarbon contributions to marine sediments from natural oil seeps, coal and organic matter (e.g., kerogen) associated with eroding siliciclastic rocks. The samples from oil seeps show extensive loss of low-molecular weight n-alkanes (<n-C14) and the presence of large, bimodal unresolved complex mixtures (UCMs), in contrast to the hydrocarbon fingerprints on the SPM and riparian sediment samples collected upstream from the oil seeps. After entering the fluvial systems, hydrocarbons from seep oils are rapidly diluted, and associate with the SPM phase as oil-mineral-aggregates (OMA). Johnston Creek, the watershed containing the most prolific seep, conveys detectable seep-derived hydrocarbons to the Gulf of Alaska, but overall seep inputs are largely attenuated by the (non-seep) petrogenic hydrocarbon content of the high SPM loads. In contrast to the geochemical signature of seep oil, Gulf of Alaska benthic sediments are characterized by abundant alkylated naphthalene homologues, relatively smooth n-alkane envelopes (n-C9 through n-C34, but with elevated levels of n-C27, n-C29, and n-C31), and small UCMs. Further, hydrocarbons in benthic sediments are highly intercorrelated. Taken together, these characteristics indicate that seep oil is a negligible petrogenic hydrocarbon source to the Gulf of Alaska continental shelf. Coaly material separated from the benthic sediment samples using a dense liquid (???2.00 g cm-3) also accounted for a minor portion of the total PAH (1-6%) and total n-alkanes (0.4-2%) in the benthic samples. Most of the hydrocarbon burden in the sediments is found in the denser sediment fraction and likely derives from organic matter contributed by denudation of siliciclastic formations in the Yakutat terrane. We therefore conclude that previous investigations relying on source allocation models have considerably overestimated oil seeps as a hydrocarbon source to the Gulf of Alaska. ?? 2006 Elsevier Ltd. All rights reserved.

Organic Geochemistry↗

USGS2006

Geochemical investigation of the potential for mobilizing non-methane hydrocarbons during carbon dioxide storage in deep coal beds

Coal samples of different rank (lignite to anthracite) were extracted in the laboratory with supercritical CO2 (40 ??C; 10 MPa) to evaluate the potential for mobilizing non-methane hydrocarbons during CO2 storage (sequestration) or enhanced coal bed methane recovery from deep (???1-km depth) coal beds. The total measured alkane concentrations mobilized from the coal samples ranged from 3.0 to 64 g tonne-1 of dry coal. The highest alkane concentration was measured in the lignite sample extract; the lowest was measured in the anthracite sample extract. Substantial concentrations of polycyclic aromatic hydrocarbons (PAHs) were also mobilized from these samples: 3.1 - 91 g tonne-1 of dry coal. The greatest amounts of PAHs were mobilized from the high-volatile bituminous coal samples. The distributions of aliphatic and aromatic hydrocarbons mobilized from the coal samples also varied with rank. In general, these variations mimicked the chemical changes that occur with increasing degrees of coalification and thermal maturation. For example, the amount of PAHs mobilized from coal samples paralleled the general trend of bitumen formation with increasing coal rank. The coal samples yielded hydrocarbons during consecutive extractions with supercritical CO2, although the amount of hydrocarbons mobilized declined with each successive extraction. These results demonstrate that the potential for supercritical CO2 to mobilize non-methane hydrocarbons from coal beds, and the effect of coal rank on this process, are important to consider when evaluating deep coal beds for CO2 storage.

Energy and Fuels↗

USGS2004

Analysis of modern and Pleistocene hydrologic exchange between Saginaw Bay (Lake Huron) and the Saginaw Lowlands area

Two numerical models, one simulating present groundwater flow conditions and one simulating ice-induced hydraulic loading from the Port Huron ice advance, were used to characterize both modern and Pleistocene groundwater exchange between the Michigan Basin and near-surface water systems of Saginaw Bay (Lake Huron) and the surrounding Saginaw Lowlands area. These models were further used to constrain the origin of saline, isotopically light groundwater, and porewater from the study area. Output from the groundwater-flow model indicates that, at present conditions, head in the Marshall aquifer beneath Saginaw Bay exceeds the modern lake elevation by as much as 21 m. Despite this potential for flow, simulated ground-water discharge through the Saginaw Bay floor constitutes only 0.028 m 3 s −1 (∼1 cfs). Bedrock lithology appears to regulate the rate of groundwater discharge, as the portion of the Saginaw Bay floor underlain by the Michigan confining unit exhibits an order of magnitude lower flux than the portion underlain by the Saginaw aquifer. The calculated shoreline discharge of groundwater to Saginaw Bay is also relatively small (1.13 m 3 s −1 or ∼40 cfs) because of low gradients across the Saginaw Lowlands area and the low hydraulic conductivities of lodgement tills and glacial-lake clays surrounding the bay. In contrast to the present groundwater flow conditions, the Port Huron ice-induced hydraulic-loading model generates a groundwater-flow reversal that is localized to the region of a Pleistocene ice sheet and proglacial lake. This area of reversed vertical gradient is largely commensurate with the distribution of isotopically light groundwater presently found in the study area. Mixing scenarios, constrained by chloride concentrations and δ 18 O values in porewater samples, demonstrate that a mixing event involving subglacial recharge could have produced the groundwater chemistry currently observed in the Saginaw Lowlands area. The combination of models and mixing scenarios indicates that structural control is a major influence on both the present and Pleistocene flow systems.

Michigan↗

USGS2002

Low-maturity Kulthieth Formation coal: A possible source of polycyclic aromatic hydrocarbons in benthic sediment of the northern Gulf of Alaska

The successful application of forensic geology to contamination studies involving natural systems requires identification of appropriate endmembers and an understanding of the geologic setting and processes affecting the systems. Studies attempting to delineate the background, or natural, source for hydrocarbon contamination in Gulf of Alaska (GOA) benthic sediments have invoked a number of potential sources, including seep oils, source rocks, and coal. Oil seeps have subsequently been questioned as significant sources of hydrocarbons present in benthic sediments of the GOA in part because the pattern of relative polycyclic aromatic hydrocarbon (PAH) abundance characteristic of benthic GOA sediments is inconsistent with patterns typical of weathered seep oils. Likewise, native coal has been dismissed in part because ratios of labile hydrocarbons to total organic carbon (e.g. PAH:TOC) for Bering River coal field (BRCF) sources are too low - i.e. the coals are over mature - to be consistent with GOA sediments. We present evidence here that native coal may have been prematurely dismissed, because BRCF coals do not adequately represent the geochemical signatures of coals elsewhere in the Kulthieth Formation. Contrary to previous thought, Kulthieth Formation coals east of the BRCF have much higher PAH: TOC ratios, and the patterns of labile hydrocarbons in these low thermal maturity coals suggest a possible genetic relationship between Kulthieth Formation coals and nearby oil seeps on the Sullivan anticline. Analyses of low-maturity Kulthieth Formation coal indicate the low maturity coal is a significant source of PAH. Source apportionment models that neglect this source will underestimate the contribution of native coals to the regional background hydrocarbon signature. ?? Published by Elsevier Science Ltd. on behalf of AEHS.

Environmental Forensics↗

USGS1999

Nearshore versus offshore copper loading in Lake Superior sediments: Implications for transport and cycling

A thorough understanding of the fate and transport of metals in Lake Superior is necessary in order to predict the ability of Lake Superior to recover from anthropogenic perturbations (copper mining). Sediment cores were collected from nearshore and offshore sites in Lake Superior and used to evaluate spatial and temporal variations in copper loading associated with mining-related activities. Although both settings have been strongly affected by anthropogenic releases of copper, copper concentrations in nearshore cores are significantly greater than those found in offshore cores, implying that nearshore copper loading is dominated by simple deposition and burial of sediment generated from mining activities. Temporal variations in copper profiles in sediments from nearshore environments closelymimic copper production rates. Conversely, copper loading histories derived from offshore sediments are not well correlated to production rates. The offshore sediment cores, when compared with analogous cores from Lakes Ontario and Michigan, show that the average, lake-wide intensity of copper loading in Lake Superior is comparable to the other two lakes, despite the fact that Lake Superior has received the largest total burden of anthropogenic copper. Cu/Zn ratios, used to evaluate the amount of copper loading derived from mining discharges, vary strongly in nearshore environments in response to loading. Cu/Zn ratios in offshore sediments are much less variable, implying that copper loading may be regulated by additional mechanisms (solution chemistry and/or biologic uptake). Study of trace metal partitioning within Lake Superior sediments indicates that the organic fraction of the sediment contains the majority of the copper. Copper concentrations in offshore sediments are significantly correlated to organic carbon content of the sediment whereas copper concentrations in nearshore sediments are not. These findings support the model that transport and deposition of particles released from mining discharges dominate copper loading in nearshore sediments, whereas biologic uptake and settling of particulate organic matter may regulate copper loading in offshore sediments.

Journal of Great Lakes Research↗

USGS1999

Ground-water, large-lake interactions in Saginaw Bay, Lake Huron: A geochemical and isotopic approach

Delineating the nature and extent of ground-water inputs is necessary to understand the hydrochemistry of large lakes. Characterizing the interaction between ground water and large lakes (e.g., the Great Lakes) is facilitated by the use of geochemical and isotopic data. In this study, pore waters were extracted from sediment cores collected from Saginaw Bay and the surrounding Saginaw lowland area; the geochemistry and stable isotope signature of these pore waters were used to identify sources for the water and solutes. Cores from Saginaw Bay and the Saginaw lowland area yielded strong vertical gradients in chloride concentrations, suggesting that a high-chloride source is present at depth. The spatial distribution of cores with elevated chloride concentrations corresponds to the regional distribution of chloride in ground water. Most of the Saginaw lowland area cores contain water with significantly lower δ 18 O values than modern meteoric water, suggesting that the water had been recharged during a much cooler climate. The δ 18 O values measured in pore waters (from Saginaw Bay cores) containing high chloride concentrations are similar to modern meteoric water; however, values lighter than modern meteoric water are encountered at depth. Chloride:bromide ratios, used to distinguish between different chloride sources, identify formation brine as the likely source for chloride. Transport models indicate that a combination of advection and diffusion is responsible for the observed Saginaw lowland area pore-water profiles. Pore-water profiles in Saginaw Bay sediments are produced primarily by diffusion and require significantly less time to evolve. An upward flux of solutes derived from formation brine could occur elsewhere within the Great Lakes region and significantly affect the geochemical cycling of chloride and other contaminants (e.g., trace metals).

Michigan↗