Geology topics

Peter H. Barry

Publications and source records attributed to Peter H. Barry.

7 recordsLinked to original sources

USGS2021

The triple argon isotope composition of groundwater on ten-thousand-year timescales

Understanding the age and movement of groundwater is important for predicting the vulnerability of wells to contamination, constraining flow models that inform sustainable groundwater management, and interpreting geochemical signals that reflect past climate. Due to both the ubiquity of groundwater with order ten-thousand-year residence times and its importance for climate reconstruction of the last glacial period, there is a strong need for improving geochemical dating tools on this timescale. Whereas 14 C of dissolved inorganic carbon and dissolved 4 He are common age tracers for Late Pleistocene groundwater, each is limited by systematic uncertainties related to aquifer composition and lithology, and the extent of water-rock interaction. In principle, radiogenic 40 Ar in groundwater acquired from decay of 40 K in aquifer minerals should be insensitive to some processes that impact 14 C and 4 He and thus represent a useful, complementary age tracer. In practice, however, detection of significant radiogenic 40 Ar signals in groundwater has been limited to a small number of studies of extremely old groundwater (>100 ka). Here we present the first high-precision (<1‰) measurements of triple Ar isotopes ( 40 Ar, 38 Ar, 36 Ar) in groundwater. We introduce a model that distinguishes radiogenic 40 Ar from atmospheric 40 Ar by using the non-radiogenic Ar isotopes ( 36 Ar, 38 Ar) to correct for mass-dependent fractionation. Using this model, we investigate variability in radiogenic 40 Ar excess (Δ 40 Ar) across 58 groundwater samples collected from 36 wells throughout California (USA). We find that Δ 40 Ar ranges from ~0‰ (the expected minimum value) to +4.2‰ across three study areas near Fresno, San Diego, and the western Mojave Desert. Based on measurements from a network of 23 scientific monitoring wells in San Diego, we find evidence for a strong dependence of Δ 40 Ar on aquifer lithology. We suggest that Δ 40 Ar is fundamentally controlled by the weathering of old K-bearing minerals and thus reflects both the degree of groundwater-rock interaction, which is related to groundwater age, and the integrated flow through different geological formations. Future studies of Late Pleistocene groundwater may benefit from high-precision triple Ar isotope measurements as a new tool to better interpret 14 C- and 4 He-based constraints on groundwater age and flow.

Chemical Geology↗

USGS2021

Noble gas signatures constrain oil-field water as the carrier phase of hydrocarbons occurring in shallow aquifers in the San Joaquin Basin, USA

Noble gases record fluid interactions in multiphase subsurface environments through fractionation processes during fluid equilibration. Water in the presence of hydrocarbons at the subsurface acquires a distinct elemental signature due to the difference in solubility between these two fluids. We find the atmospheric noble gas signature in produced water is partially preserved after hydrocarbons production and water disposal to unlined ponds at the surface. This signature is distinct from meteoric water and can be used to trace oil-field water seepage into groundwater aquifers. We analyse groundwater ( n = 30) and fluid disposal pond ( n = 2) samples from areas overlying or adjacent to the Fruitvale, Lost Hills, and South Belridge Oil Fields in the San Joaquin Basin, California, USA. Methane (2.8 × 10 −7 to 3 × 10 −2 cm 3 STP/cm 3 ) was detected in 27 of 30 groundwater samples. Using atmospheric noble gas signatures, the presence of oil-field water was identified in 3 samples, which had equilibrated with thermogenic hydrocarbons in the reservoir. Two (of the three) samples also had a shallow microbial methane component, acquired when produced water was deposited in a disposal pond at the surface. An additional 6 samples contained benzene and toluene, indicative of interaction with oil-field water; however, the noble gas signatures of these samples are not anomalous. Based on low tritium and 14 C contents (≤ 0.3 TU and 0.87–6.9 pcm, respectively), the source of oil-field water is likely deep, which could include both anthropogenic and natural processes. Incorporating noble gas analytical techniques into the groundwater monitoring programme allows us to 1) differentiate between thermogenic and microbial hydrocarbon gas sources in instances when methane isotope data are unavailable, 2) identify the carrier phase of oil-field constituents in the aquifer (gas, oil-field water, or a combination), and 3) differentiate between leakage from a surface source (disposal ponds) and from the hydrocarbon reservoir (either along natural or anthropogenic pathways such as faulty wells).

California↗

USGS2021

Groundwater residence time estimates obscured by anthropogenic carbonate

Groundwater is an important source of drinking and irrigation water. Dating groundwater informs its vulnerability to contamination and aids in calibrating flow models. Here, we report measurements of multiple age tracers ( 14 C, 3 H, 39 Ar, and 85 Kr) and parameters relevant to dissolved inorganic carbon (DIC) from 17 wells in California’s San Joaquin Valley (SJV), an agricultural region that is heavily reliant on groundwater. We find evidence for a major mid-20th century shift in groundwater DIC input from mostly closed- to mostly open-system carbonate dissolution, which we suggest is driven by input of anthropogenic carbonate soil amendments. Crucially, enhanced open-system dissolution, in which DIC equilibrates with soil CO 2 , fundamentally affects the initial 14 C activity of recently recharged groundwater. Conventional 14 C dating of deeper SJV groundwater, assuming an open system, substantially overestimates residence time and thereby underestimates susceptibility to modern contamination. Because carbonate soil amendments are ubiquitous, other groundwater-reliant agricultural regions may be similarly affected.

California↗

USGS2021

Research, monitoring, and evaluation of emerging issues and measures to recover the Snake River Fall Chinook salmon ESU

The portion of the Snake River fall Chinook salmon Oncorhynchus tshawytscha evolutionary significant unit (ESU) that spawns upstream of Lower Granite Dam transitioned from low to high abundance during 1992–2020 in response to U.S. Endangered Species Act recovery efforts and other federally mandated actions. This annual report focuses on changes in population abundance and habitat use by natural- and hatchery-origin spawners. Typically, we also report on population attributes of natural-origin juveniles, but data on juveniles were not collected in 2020 due to Covid-19. Spawners have located and used most of the available spawning habitat and that habitat is gradually approaching the point that no more redds can be supported. Timing of spawning and fry emergence have been relatively stable, but effects of density dependence are evident in juvenile life stages. Apparent abundance of juvenile fall Chinook salmon has increased and we noted the following changes: parr dispersal from riverine rearing habitat into Lower Granite Reservoir has become earlier; growth rate (g/d) and dispersal size of parr has declined; and passage timing of smolts from the two Snake River reaches has become earlier and downstream movement rate has increased. These findings coupled with stock-recruitment analyses presented in this report provide evidence for density-dependence in the Snake River reaches and in Lower Granite Reservoir resulting from the expansion of the recovery program. The long-term goal is to use this information in a comprehensive modeling effort to conduct action-effectiveness and uncertainty research and to inform Fish Population, Hydrosystem, Harvest, Hatchery, and Predation and Invasive Species Management Research, Monitoring, and Evaluation (RM&E) programs. In 2020, the U.S. Geological Survey (USGS) focused survey efforts in the Snake River on deepwater redd searches and fish collection for parentage-based tagging (PBT) analyses. We use a boat-mounted underwater video camera to count 170 deepwater redds at 19 of the 28 sites surveyed. Redd depths averaged 4.2 m. We collected genetic samples from 297 live fall Chinook salmon and 16 carcasses at 44 unique geographic locations that spanned 89 river kilometers. Seventy-two fish were recovered at Eureka Bar (rkm 307.1) and Corral Creek (rkm 349.7), which accounted for 23% of all collected fish in 2020. Most (238 fish) post-spawned salmon were collected from early to mid-November just after peak spawning. A summary of 2019 PBT results can be found in Appendix A.1. In 2020, we PIT tagged subyearling fall Chinook salmon in the Clearwater River to obtain population and growth data. In the Clearwater River, we tagged 2,192 subyearlings and recaptured 79 (3.6%) fish in the river and 187 fish (78 tagged by the U.S. Geological Survey, 109 tagged by the Nez Perce Tribe) at Lower Granite Dam during October which provided information for growth estimation. Within riverine habitats, growth in both length and mass were higher for fish tagged with 8-mm tags than with 9- and 12-mm tags. Estimated growth in length and mass of subyearlings was generally lower in Lower Granite Reservoir than in riverine habitats. Information on prey resources and juvenile fall Chinook salmon prey consumption was collected to better understand the growth opportunity of late-migrating fish in Lower Granite Reservoir. Zooplankton and surface drifting prey were collected from three reservoir locations from July through October during 2019 and 2020. Fall Chinook salmon diet data were collected from angled fish using gastric lavage. Cladocera and Copepoda were the most abundant zooplankton taxa collected while Diptera was the most common invertebrate taxon collected in surface drift samples. Totals of 49 and 94 juvenile fall Chinook salmon were captured in 2019 and 2020, respectively, and most fish were caught in the lower reach of the reservoir in October of each year. Juvenile fall Chinook salmon consumed mainly dipterans in July and October 2019 and mainly Daphnia during August–October in 2020. Fish showed selection mainly for dipterans in 2019 but strong selection for Daphnia during October 2020. Stomach fullness values were relatively low (<1.1%) during both years. Results show that prey resources are adequate in Lower Granite Reservoir to support positive fish growth during late summer and early autumn.

Idaho, Oregon, Washington↗

USGS2019

Occurrence and sources of radium in groundwater associated with oil fields in the southern San Joaquin Valley, California

Geochemical data from 40 water wells were used to examine the occurrence and sources of radium (Ra) in groundwater associated with three oil fields in California (Fruitvale, Lost Hills, South Belridge). 226Ra+228Ra activities (range=0.010-0.51 Bq/L) exceeded the 0.185 Bq/L drinking-water standard in 18% of the wells (not drinking-water wells). Radium activities were correlated with TDS concentrations (p<0.001, ρ=0.90, range=145-15,900 mg/L), Mn+Fe concentrations (p<0.001, ρ=0.82, range=<0.005-18.5 mg/L), and pH (p<0.001, ρ=-0.67, range=6.2-9.2), indicating Ra in groundwater was influenced by salinity, redox, and pH. Ra-rich groundwater was mixed with up to 45% oil-field water at some locations, primarily infiltrating through unlined disposal ponds, based on Cl, Li, noble-gas, and other data. Yet 228Ra/226Ra ratios in pond-impacted groundwater (median=3.1) differed from those in oil-field water (median=0.51). PHREEQC mixing calculations and spatial geochemical variations suggest the Ra in oil-field water was removed by co-precipitation with secondary barite and adsorption on Mn-Fe precipitates in the near-pond environment. The saline, organic-rich oil-field water subsequently mobilized Ra from downgradient aquifer sediments via Ra-desorption and Mn/Fe-reduction processes. This study demonstrates that infiltration of oil-field water may leach Ra into groundwater by changing salinity and redox conditions in the subsurface rather than by mixing with a high-Ra source.

California↗

USGS2018

Tracing enhanced oil recovery signatures in casing gases from the Lost Hills oil field using noble gases

Enhanced oil recovery (EOR) and hydraulic fracturing practices are commonly used methods to improve hydrocarbon extraction efficiency; however the environmental impacts of such practices remain poorly understood. EOR is particularly prevalent in oil fields throughout California where water resources are in high demand and disposal of high volumes of produced water may affect groundwater quality. Consequently, it is essential to better understand the fate of injected (EOR) fluids in California and other subsurface petroleum systems, as well as any potential effect on nearby aquifer systems. Noble gases can be used as tracers to understand hydrocarbon generation, migration, and storage conditions, as well as the relative proportions of oil and water present in the subsurface. In addition, a noble gas signature diagnostic of injected (EOR) fluids can be readily identified. We report noble gas isotope and concentration data in casing gases from oil production wells in the Lost Hills oil field, northwest of Bakersfield, California, and injectate gas data from the Fruitvale oil field, located within the city of Bakersfield. Casing and injectate gas data are used to: 1) establish pristine hydrocarbon noble-gas signatures and the processes controlling noble gas distributions, 2) characterize the noble gas signature of injectate fluids, 3) trace injectate fluids in the subsurface, and 4) construct a model to estimate EOR efficiency. Noble gas results range from pristine to significantly modified by EOR, and can be best explained using a solubility exchange model between oil and connate/formation fluids, followed by gas exsolution upon production. This model is sensitive to oil-water interaction during hydrocarbon expulsion, migration, and storage at reservoir conditions, as well as any subsequent modification by EOR.

California↗

USGS2013

Volatile ﬂuxes through the Big Bend section of the San Andreas Fault, California: helium and carbon-dioxide systematics

To investigate the source of volatiles and their relationship to the San Andreas Fault System (SAFS), 18 groundwater samples were collected from wells near the Big Bend section of the SAFS in southern California and analyzed for helium and carbon abundance and isotopes. Concentrations of 4 He, corrected for air-bubble entrainment, vary from 4.15 to 62.7 (× 10 − 8 ) cm 3 STP g − 1 H 2 O. 3 He/ 4 He ratios vary from 0.09 to 3.52 R A (where R A = air 3 He/ 4 He), consistent with up to 44% mantle helium in samples. A subset of 10 samples was analyzed for the major volatile phase (CO 2 ) — the hypothesized carrier phase of the helium in the mantle–crust system: CO 2 / 3 He ratios vary from 0.614 to 142 (× 10 11 ), and δ 13 C (CO 2 ) values vary from − 21.5 to − 11.9‰ (vs. PDB). 3 He/ 4 He ratios and CO 2 concentrations are highest in the wells located in the Mil Potrero and Cuddy valleys adjacent to the SAFS. The elevated 3 He/ 4 He ratios are interpreted to be a consequence of a mantle volatile flux though the SAFS diluted by radiogenic He produced in the crust. Samples with the highest 3 He/ 4 He ratios also had the lowest CO 2 / 3 He ratios. The combined helium isotope, He–CO 2 elemental relationships, and δ 13 C (CO 2 ) values of the groundwater volatiles reveal a mixture of mantle and deep crustal (metamorphic) fluid origins. The flux of fluids into the seismogenic zone at high hydrostatic pressure may cause fault rupture, and transfer volatiles into the shallow crust. We calculate an upward fluid flow rate of 147 mm a − 1 along the SAFS, up to 37 times higher than previous estimates (Kennedy et al., 1997). However, using newly identified characteristics of the SAFS, we calculate a total flux of 3 He along the SAFS of 7.4 × 103 cm 3 STP a − 1 (0.33 mol 3 He a − 1 ), and a CO 2 flux of 1.5 × 10 13 cm 3 STP a − 1 (6.6 × 10 8 mol a − 1 ), ~ 1% of previous estimates. Lower fluxes along the Big Bend section of the SAFS suggest that the flux of mantle volatiles alone is insufficient to cause the super hydrostatic pressure in the seismogenic zone; however, results identify crustal (metamorphic) fluids as a major component of the CO 2 volatile budget, which may represent the additional flux necessary for fault weakening pressure in the SAFS.

California↗