Using fossil spring deposits in the Death Valley region, USA to evaluate palaeoflowpaths

Abstract

Spring deposits reveal the timing and environment of past groundwater discharge. Herein, however, the potential for fossil spring deposits to infer water sources and palaeoflowpaths through trace elements and stable and radiogenic isotopes is examined.Past discharge (70 to 285 ka) in the Tecopa Basin in the Death Valley region of southeastern California is represented by tufa deposits, including mounds, pools, cemented ledges and rare calcite feeder veins. d 18 O values indicate that spring discharge was a mixture of far-travelled (regional) water with a significant, and perhaps dominant contribution of local recharge on a nearby range front and alluvial pediment, rather than simply representing an elevated regional water table. d 13 C values indicate regional water had a high TDS, whereas solute data imply low overall solute contents, consistent with dilution by a large component of local recharge.Radiogenic isotope data (U-series, 87 Sr/ 86 Sr) for tufa indicate that siliciclastic rocks (a regional aquitard) interacted with discharging water. To access this aquitard, regional flow was probably partitioned into a permeable north-south damage zone of a north-south range-bounding fault along the foot of the Resting Spring Range, which ultimately controlled the location of groundwater discharge. Existing models for modern discharge in the Tecopa Basin, by contrast, call upon westward interbasin flow in carbonate rocks from the Spring Mountains through the intervening (and nearly perpendicular) Nopah and Resting Spring Ranges. Understanding the controls on regional groundwater flow is critical in this and other arid regions where water is, by definition, a scarce resource. Thus, although it is a case study, this report highlights a fruitful approach to palaeohydrology that can be widely applied.

A structural study of thermal tufas using ground-penetrating radar

“…The study of tufas can benefit constraining models of climate change and paleo-hydrological reconstructions. The spatial and temporal distribution of tufa depends on groundwater recharge, which is controlled by climate variation (Evans, 1999;Miner et al, 2007;Pedley et al, 1996). From a geotechnical point of view, because any calcareous deposits may be associated with underground cavities, mapping of tufa in areas undergoing urbanization may help mitigate geologic risks (Al-fares et al, 2002;Apel and Dezelic, 2005;Pipan et al, 2002).…”

Commentary and Review of Modern Environmental Problems Linked to Historic Flow Capacity in Arid Groundwater Basins

“…Case example 2 uses raw data collected by Waring and Sims and Spaulding and reinterpreted in relation to modern flow capacity [25,26]. Case examples 1 and 5 uses information developed in studies by Miner et al, Duffy and Al Hassan [27], and Hamann et al [13,17,28].…”

“…Sigstadt et al [6] used the term "underfit aquifer" for an aquifer that is well-below flow capacity, but other terms do not appear in the literature except for summary descriptions, such as "the aquifer is full" or "is at full storage capacity' quote symbol wrong? In a closely related topic, there is abundant literature on fossil spring deposits and fossil wetlands that developed in flow systems that were once at flow capacity [1,[7][8][9][10][11][12][13]. Studies of fossil springs are often related to groundwater discharge points at the end of regional flow paths, and tied to paleo-environments and long-term climate change, but not necessarily to flow capacity.…”

“…The provenance of isotope and hydrochemical species just discussed can also be applied to mineral cements deposited from ancient springs when basins were formerly at flow capacity. A variation of this concept was presented by Miner et al [13], for fossil spring deposits used to date paleo spring discharge in Tecopa Basin, Death Valley USA region. Using oxygen, strontium, and U-series isotopes in their study, a regional groundwater flow component dating back 70 to 285 ka was interpreted along a permeable north-south fault zone along the base of Resting Spring Range.…”

Modelling size constraints on carbonate platform formation in groundwater upwelling zones

“…Stable oxygen and carbon isotope analysis in combination with dating techniques of fossiliferous carbonate deposits in groundwater upwelling zones have previously been used to derive changes in climate and the onset of arid periods, as well as information about the long-term temporal dynamics of groundwater upwelling 1 – 7 . With the exception of some works that have modelled the shape of actively-forming depositional features 8 – 11 , most previous studies concerning the geochemical and sedimentological controls on spring carbonate deposition are field-based, with a particular emphasis on understanding carbonate precipitation triggers 12 .…”