2017

Death Valley

Research

Dr Yuri Dublyansky

+43-6508509494

Innsbruck University
Institute of Geology
Innrani 52
Innsbruck, Select... 6020
Austria

 

Yuri.Dublyansky@uibk.ac.at

Refining the long-term history of the water table of the Ash Meadows Groundwater Flow System (extension)

DEVA-00411

DEVA-2017-SCI-0002

Jan 10, 2017

Dec 31, 2018

Jan 09, 2017

Dec 21, 2019

Continuing

___ A final report has been provided to the park or will be provided to the park within the next two years

___ Copies of field notes, data files, photos, or other study records, as agreed, have been provided to the park

___ All collected and retained specimens and retained material originating from such specimens have been cataloged into the NPS catalog system and NPS has processed loan agreements as needed.

Research

Atmosphere / Climate / Weather

Cave / Karst

Geochemistry (inc. Minerals / Petrology)

The main objectives of this study are:
• to reconstruct, at unprecedented resolution, water-table elevations in the Devils Hole area for the last 600,000 yr, and potentially 1,000,000 yr;
• to obtain robust information on the highest water stands in the Devils Hole area (which has implications for the unresolved issue of the time of isolation of the Devils Hole pupfish); and
• to identify and date the lowermost water stands (i.e., below the modern water table position) which could shed light on the issue of the former survival of pupfish at times when the shallow spawning shelf in Devils Hole was dry.
• to extend the Devils Hole isotope paleoclimate record back in geological time beyond 600,000 yr.
The key hypothesis which will be tested using these samples is the direct relationship between the water-table elevation in the Devils Hole caves and climate (largely precipitation) on a millennial time scale. This hypothesis will be tested by comparing the U-Th dated oxygen and carbon isotope record from the Devils Hole calcite with paleowater table elevations, as well as by comparing the latter with other available regional paleohydrological proxy records (paleowater levels of Owens Lake, Owens River system, Death Valley sediments and shoreline tufas, Searles Lake, etc.; see summary by Sharpe, 2007).

In the reporting period we continued sampling mammillary calcite deposits in Devils Hole 2. All except 3 cores previously drilled above the water table were finished by extending them to the calcite/bedrock interface. Three cores drilled at or below the water table were extended from ca. 25 cm to ca. 50 cm. We could not rich the bedrock due to problems with underwater drill housing, therefore this activity had to be postponed until the next visit in February 2018.
In the reporting period, as before, research was focused on two topics: (1) developing of the history of paleo water-table elevations at Devils Hole; and (2) extending the paleoclimate record back in time. The topic (3) - Improvement of the existing isotopic paleoclimate record received less attention primarily, because most of the work on it was already done.
Topic 1 (paleo water-table). In addition to ca. 50 U-Th dated acquired in 2015, and 60 U-Th dates acquired in 2015, some 50 more U-Th dates were obtained. This was necessary to better constrain high-water stands, marked by deposition of calcite folia layers.
Topic 2 (old paleoclimate). 234U-238U method was tested and applied to extend the record past 600,000 years (the U-Th dating limit). We also performed several tests preparatory for the paleomagnetic dating.
Topic 3 (paleoclimate). Based on discussion, generated by our 2016 publication in Science (Moseley G., Edwards L.R., Wendt K., Cheng H., Dublyansky Y., Lu Y., Boch R., Spötl C. (2016): Science 351; Winograd I.J. (2016): Science 354; Coplen T.B. (2016): Science 354; Moseley G.E., Dublyansky Y.V., Edwards R.L. Wendt K.A., Pythoud M., Zhang P., Cheng H., Lu Y., Boch R., Spötl C. (2016): Science 354), we strived to obtain the data on the U and Th contents and isotope compositions in the water column of Devils Hole II. In this effort we were assisted by cave diver Brian Kakuk, who performed a dive to 300 ft-depth when filming episode of IMAX movie “Ancient Caves” (directed by Jonathan Bird). Brian collected for our project water samples from 5 different depths; samples were treated in the facilities of the Pahrump Office of DVNP and then analyzed at the Minnesota University. These measurements confirmed that previously established 238U concentrations in DH2 cave water @ 3 ppb and very low, ~50 femtogram per gram Th concentrations.
Brian also collected a sample of mammillary calcite from depth -46 m. The sample will be studied in the future (U-Th dating, stable isotopes).
Patching of cores. In order to minimize visual impact of our activities in the cave, those cores that were completed (extended to calcite/bedrock interface) were patched using lime putty/sand mixture and subsequently camouflaged using local pigments (primarily clay and silt from the cave).

Yes

The collected specimens are in the form of 1 inch-diameter cores, taken across the layers of mammillary calcite.
One sample was collected as a piece of rock chipped of by a diver at a depth -46 m.
Water samples were collected in plastic collapsible containers 1 L and 0.2 L (from each collection depth).