@article {2989,
	title = {The triple argon isotope composition of groundwater on ten-thousand-year timescales},
	journal = {Chemical Geology},
	volume = {583},
	year = {2021},
	month = {11/2021},
	pages = {120458},
	abstract = {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 14C of dissolved inorganic carbon and dissolved 4He 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 40Ar in groundwater acquired from decay of 40K in aquifer minerals should be insensitive to some processes that impact 14C and 4He and thus represent a useful, complementary age tracer. In practice, however, detection of significant radiogenic 40Ar 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{\textperthousand}) measurements of triple Ar isotopes (40Ar, 38Ar, 36Ar) in groundwater. We introduce a model that distinguishes radiogenic 40Ar from atmospheric 40Ar by using the non-radiogenic Ar isotopes (36Ar, 38Ar) to correct for mass-dependent fractionation. Using this model, we investigate variability in radiogenic 40Ar excess (Δ40Ar) across 58 groundwater samples collected from 36 wells throughout California (USA). We find that Δ40Ar ranges from ~0{\textperthousand} (the expected minimum value) to +4.2{\textperthousand} 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 Δ40Ar on aquifer lithology. We suggest that Δ40Ar 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 14C- and 4He-based constraints on groundwater age and flow.},
	keywords = {groundwater, Groundwater dating, Isotope geochemistry, Noble gas},
	isbn = {0009-2541},
	doi = {10.1016/j.chemgeo.2021.120458},
	url = {https://www.sciencedirect.com/science/article/pii/S0009254121004010},
	author = {Seltzer, Alan M. and Krantz, John A. and Ng, Jessica and Danskin, Wesley R. and Bekaert, David V. and Barry, Peter H. and Kimbrough, David L. and Kulongoski, Justin T. and Severinghaus, Jeffrey P.}
}
@article {2531,
	title = {Compilation of geophysical, geochronological, and geochemical evidence indicates a rapid Mediterranean-derived submergence of the Black Sea{\textquoteright}s shelf and subsequent substantial salinification in the early Holocene},
	journal = {Marine Geology},
	volume = {383},
	year = {2017},
	month = {Jan-01-2017},
	pages = {14 - 34},
	abstract = {Our knowledge of rate and processes in which semi-enclosed environments alternate from lacustrine to marine is commonly limited because of the paucity of specific proxies for sea level and salinity. Here we investigate the timing, rate, and key mechanisms involved in the transformation of the previously isolated Black Sea-Lake to the modern partly-enclosed marine sea using a suite of geophysical, geochemical, and geochronological methods.

Cores were collected in transects across shelves of Ukraine, Romania, Bulgaria, and Turkey. Biogenic carbonate from these cores was analyzed for radiocarbon and strontium, oxygen, and carbon isotopes. Strontium results indicate that the submergence of the Black Sea shelf at 9300 calendar years BP was caused by the ingress of Mediterranean water and was abrupt, taking < 40 years. The seismic reflection profiles show a uniform drape of subsequent sediment over aeolian dunes indicating a drowning with no time for erosion accompanying the submergence. Moisture measurements beneath the uniform drape indicate that the shelf was dry before submergence and the shoreline of the Preboreal lake may have regressed to beyond 120 mbsl. Mollusks colonized the newly submerged substrate of the inner shelf at the same time as they colonized the outer shelf. The succession of mollusk species with shells whose strontium isotope composition has a marine component indicates a rising salinity. The transformation of the lake to a sea is affirmed by increases in the shells{\textquoteright} strontium and oxygen isotopic ratios towards the external ocean value.

Radiocarbon years are calibrated to calendar years by tuning the oxygen and carbon isotope composition of the mollusk record to that of the U/Th dated Sofular Cave stalagmites. The match shows a reduction of the lake{\textquoteright}s prior high reservoir age accompanying the inflow of the Mediterranean water. In 900 years the salinity reached a threshold that excluded all previous Black Sea lacustrine fauna. These results imply that any substantial postglacial submergence of the Black Sea shelves did not occur prior to entry of Mediterranean water.},
	keywords = {Black Sea, Black Sea transgression, Isotope geochemistry, Lake transgression, Marine-lake connections, paleoceanography, paleosalinity, Reflection profiles},
	issn = {00253227},
	doi = {10.1016/j.margeo.2016.11.001},
	url = {https://doi.org/10.1016/j.margeo.2016.11.001},
	author = {Yanchilina, Anastasia G. and Ryan, William B.F. and McManus, Jerry F. and Dimitrov, Petko and Dimitrov, Dimitar and Slavova, Krasimira and Filipova-Marinova, Mariana}
}
@article {1878,
	title = {Oxygen and carbon isotope records of calcareous nannofossils from the west Philippine Sea during the last 190ka},
	journal = {Earth Science.Journal of China University of Geoscience},
	volume = {33},
	year = {2008},
	note = {id: 1933; NO: Source type: scholarlyjournals; Object type: Article; Copyright: GeoRef in Process, Copyright 2011, American Geosciences Institute. After editing and indexing, this record will be added to Georef.; CSAUnique: 570969-5; AccNum: 570969-5; ISSN: 1000-2383; Peer Reviewed: true},
	month = {2008},
	pages = {183-183-189},
	abstract = {The piston core Ph05-5 recovered from the West Philippine Sea(16.049 degrees N, 124.344 degrees E, water depth 3382m) was used to study the delta (super 18) O and delta (super 13) C variations of calcareous nannofossils. The delta (super 18) O values of calcareous nannofossils were obviously lower in Holocene and the last interglaciation than those in the last and the penultimate glaciation. During the last 190 ka the nannofossil delta (super 18) O values were positively correlated with those of planktonic and benthic foraminifera from the same core. But the average delta (super 18) O value of nannofossils was 0.431X10 (super -3) , higher than that of planktonic foraminifera Globigerinoides rubber, and was 0.410X10 (super -3) , lower than that of planktonic foraminifera Neogloboquadrina dutertrei. All the above three average delta (super 18) O values were much lower than those of benthic foraminifera Cibicides wullerstorfi. The change of nannofossil delta (super 13) C values showed similar trends with the absolute abundance of calcareous nannofossils in core Ph05-5, which also indicates the primary productivity variations in the West Philippine Sea. The primary productivity stayed at a stable but relatively low level at MIS 6 and MIS 5e.There was an abrupt rise at the beginning of MIS 5d for the primary productivity which retained high value until 25 ka BP. The primary productivity showed a slight decline during MIS 2 and MIS 1, but still higher than that of MIS 6 and MIS 5e.},
	keywords = {02D, 24, algae, biochemistry, C-13/C-12, carbon, Cenozoic, Foraminifera, Geochemistry, Holocene, Invertebrata, Isotope geochemistry, isotope ratios, isotopes, Last glacial maximum, microfossils, nannofossils, north pacific, Northwest Pacific, O-18/O-16, oxygen, Pacific Ocean, paleo-oceanography, Philippine Sea, Plantae, Pleistocene, productivity, Protista, Quaternary, Quaternary geology, Stable isotopes, upper Pleistocene, West Pacific},
	isbn = {1000-2383, 1000-2383},
	author = {Jingtao, Zhao and Li, Tiegang and Chang, Fengming and Li, Jun}
}
@conference {1758,
	title = {Progress of the NOSAMS facility WOCE (super 14) C data analysis},
	volume = {38},
	year = {1996},
	note = {id: 2242; Source type: conferencepapers\&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1999-071631; AccNum: 1999-071631; ISSN: 0033-8222; CODEN: RACAAT},
	month = {1996},
	pages = {123},
	publisher = {University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA)},
	organization = {University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA)},
	address = {United States (USA)},
	keywords = {02D, 07, accelerator mass spectroscopy, C-14, carbon, Isotope geochemistry, isotopes, mass spectroscopy, Oceanography, Pacific Ocean, progress report, radioactive isotopes, report, sea water, spectroscopy},
	author = {von Reden, K. F. and McNichol, A. P. and Schneider, Robert J.}
}
@conference {1794,
	title = {Stable and radio-carbon isotope measurements in the Pacific Ocean; contributions from NOSAMS},
	volume = {77},
	year = {1996},
	note = {id: 2240; Source type: conferencepapers\&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1997-047916; AccNum: 1997-047916; ISSN: 0096-3941; CODEN: EOSTAJ},
	month = {1996},
	pages = {79},
	publisher = {American Geophysical Union, Washington, DC, United States (USA)},
	organization = {American Geophysical Union, Washington, DC, United States (USA)},
	address = {United States (USA)},
	keywords = {02D, 07, accelerator mass spectroscopy, C-13/C-12, C-14, carbon, chemical analysis, geochemical indicators, high-resolution methods, Isotope geochemistry, isotope ratios, isotopes, marine geology, mass spectroscopy, National Ocean Sciences Accelerator Mass Spectrometry, NOSAMS, Oceanography, Pacific Ocean, radioactive isotopes, radioactive tracers, sampling, sea water, spectroscopy, Stable isotopes, tracers, Woods Hole Oceanographic Institution},
	author = {McNichol, A. P. and von Reden, K. F. and Schneider, R. J. and Key, R. M. and Jones, G. A.}
}
