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A paleotemperature record derived from dissolved noble gases in groundwater of the Aquia Aquifer (Maryland, USA)

A paleotemperature record derived from dissolved noble gases in groundwater of the Aquia Aquifer (Maryland, USA),10.1016/S0016-7037(01)00804-3,Geochim

A paleotemperature record derived from dissolved noble gases in groundwater of the Aquia Aquifer (Maryland, USA)   (Citations: 42)
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Low 14C activities in groundwater of the confined part of the Aquia aquifer in southeastern Maryland suggest that most of this water infiltrated at least 30,000 years ago. However, radiocarbon contents of the dissolved inorganic carbon seem to be affected by isotopic exchange, possibly with secondary calcite deposits in the formation, leading to overestimated 14C ages. Whereas the geochemistry of the Aquia aquifer complicates the application of the widely used 14C dating method, the accumulation of radiogenic He seems to provide a viable alternative for establishing a chronology. The quasi-linear increase of He concentrations with flow distance observed in the Aquia aquifer can be explained entirely by accumulation of in situ produced radiogenic He. U and Th concentrations in Aquia sand were measured in order to determine the accumulation rate of 4He with sufficient confidence to establish a He time scale.Concentrations of dissolved atmospheric noble gases were used to derive mean annual ground temperatures at the time of infiltration. These noble gas temperatures (NGTs) clearly show the presence of water that infiltrated under much cooler conditions than at present. NGTs are correlated with chloride concentrations, corroborating the hypothesis that chloride variations in this aquifer constitute a climate signal. In contrast, the stable isotope ratios δ180 and δD do not provide a clear record of past climatic changes in the Aquia aquifer and the correlation between NGTs and stable isotope ratios is weak. The NGT record suggests that mean annual temperatures in this midlatitude coastal site during the last glacial maximum (LGM) were (9.0 ± 0.6) °C colder than during the Holocene. This difference is slightly lower than estimates derived from pollen data for this region, but considerably larger than the rather uniform cooling of about 5°C indicated by noble gas studies in more southern locations of North America. The larger cooling is ascribed to the influence of the Laurentide ice sheet, which at its maximum extension came as close as 250 km to our study site.
Journal: Geochimica Et Cosmochimica Acta - GEOCHIM COSMOCHIM ACTA , vol. 66, no. 5, pp. 797-817, 2002
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    • ...Although pre-Holocene recharge in unconfined aquifers is largely restricted to the western United States, pre-Holocene recharge is commonly found in confined aquifers throughout the country (Aeschbach-Hertig et al. 2002; Clark et al. 1998; Douglas et al. 2007; Kennedy and Genereux 2007; Klump et al. 2008; Lopes and Hoffmann 1997 ;M a et al.2004; Pearson and White 1967; Phillips et al. 1989 ;P lummer et al.1990; Plummer 1993; Plummer and ...

    P. B. McMahonet al. A comparison of recharge rates in aquifers of the United States based ...

    • ... Ne, Ar, Kr and Xe are conservative tracers and their concentrations in groundwater are determined by a small constellation of physical properties (e.g., ground temperature and altitude), NGTs have long held out the promise of providing reliable information on absolute values of paleotemperature, and have been widely used to reconstruct the past climate in continental areas [e.g., Stute and Deak, 1989; Stute and Schlosser, 1993; ...
    • ...In particular, several studies have argued that NGT records have revealed average temperature drops of � 5C relative to current temperatures during the last glacial maximum or LGM [e.g., Stute et al., 1992, 1995a; Aeschbach-Hertig et al., 2002a]...
    • ... the behavior of the different NGT models with real data, NGTs were fitted to data from the following seven study sites: (1) HP, the P flow system in Great Hungary Basin [Stute and Deak, 1989]; (2) HQ, the Q flow system in Great Hungary Basin [Stute and Deak, 1989]; (3) SJ, the San Juan basin in New Mexico [Stute et al., 1995b]; (4) MI, the Marshall aquifer in Michigan [Ma et al., 2004]; (5) MD, the Aquia aquifer in Maryland [Aeschbach-Hertig ...
    • ...New Mexico [Stute et al., 1995b]; MI, Marshall Sandstone Aquifer, Michigan [Ma et al., 2004]; MD, Aquia aquifer in Maryland [Aeschbach-Hertig et al., 2002a]; MN, Minqin Basin in China [Edmunds et al., 2006]; TX, Carrizo aquifer in Texas [Castro et al., 2007]...
    • ...[14] The results of fitting the above four NGT models to the seven data sets are shown in Figure 1. Not only are NGT values shown, but the size of the EA component is also illustrated using the DNe notation from Aeschbach-Hertig et al. [2002a], which is defined as (Nemeasured/ NeASW � 1). Excess air volume (A) is a parameter common to all four models, but only part of this volume is retained in the CE model and therefore the A parameter is ...
    • ...Figure 1. NGT and DNe records from (a) HP, the P flow system in Great Hungary Basin [Stute and Deak, 1989]; (b) HQ, the Q flow system in Great Hungary Basin [Stute and Deak, 1989]; (c) SJ, the San Juan basin in New Mexico [Stute et al., 1995b]; (d) MI, the Marshall aquifer in Michigan [Ma et al., 2004]; (e) MD, the Aquia aquifer in Maryland [Aeschbach-Hertig et al., 2002a]; (f) MN, the Minqin Basin in China [Edmunds et al., 2006]; and (g) ...

    Tie Sunet al. Statistical properties of groundwater noble gas paleoclimate models: A...

    • ... groundwater (decades old) or old groundwater (thousands of years old), and choose a tracer or group of tracers accordingly: usually CFCs, SF6, and/or 3 H/ 3 He dating for studies of young groundwater [e.g., Plummer et al., 2001; Cook et al., 2003; Tesoriero et al., 2005; Koh et al., 2006] and C isotopes or 36 Cl in studies of old groundwater [e.g.,Phillips etal., 1986;Torgersen etal.,1991;Clark et al., 1998; Plummer and Sprinkle, 2001; ...

    David P. Genereuxet al. Chemical and isotopic signature of old groundwater and magmatic solute...

    • ...[3] Most of the climatic reconstructions obtained from groundwater focus on the transition from the Pleistocene to the Holocene [Stute et al., 1995; Weyhenmeyer et al., 2000; Aeschbach-Hertig et al., 2002; Beyerle et al., 1998, 2003; Klump et al., 2008b]...

    J. A. Corcho Alvaradoet al. European climate variations over the past half-millennium reconstructe...

    • ...routine, the particular model is dismissed as a valid description of the data [Aeschbach-Hertig et al., 2002b]...
    • ...This observation is in some contrast with the usually good performance of the CE-model for samples with excess air [Aeschbach-Hertig et al., 2000, 2002b; Beyerle et al., 2003; Edmunds et al., 2006; Manning and Caine, 2007]...

    Werner Aeschbach-Hertiget al. Modeling excess air and degassing in groundwater by equilibrium partit...

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