The Death Valley Regional Flow System: A Fault-controlled Oasis for Deep
Life Beneath the Mojave Desert
Duane P. Moser, Desert Research Institute, Las Vegas, NV, USA
Concept: The Death Valley Regional Flow System (DVRFS) of Nevada and California, USA, is
a unique site for ICDP drilling at the nexus of life, geology, hydrology, and societal interests.
3D Geological Context: Located in the Basin and Range physiographic province of the Western
United States, the DVRFS is a deep, fracture-controlled aquifer that encompasses ~100,000 km2
of mountain ranges (up to 3,600 m above sea level) and valleys which can reach below sea level
(e.g. Death Valley, at -86 m, the lowest point in North America [1]). Climate is controlled by
altitude: with the highest peaks receiving ~100 cm/y of precipitation and Death Valley, the
hottest place on Earth [2] and driest place in North America, a mere ~4 cm/y [3]. DVRFS
geology is both active (Nevada is the US’ 3rd most tectonically-active state [4]) and complex;
recording tectonic and sedimentary (marine and continental), metamorphic, and intrusive igneous
histories from over 2 Ga. Geologically-significant events include: 1) formation of thick
Paleozoic (~550 Ma) marine carbonates that underlie most of the DVRFS, 2) extrusion of a
broad Tertiary (23 – 2.6 Ma) volcanic plateau in the central DVRFS, and 3) crustal extension,
from ~16 Ma to present, that created the Basin and Range and Death Valley (~2 – 3 Ma, [5]).
This region has thin crust (e.g. ~17 – 25 km under Death Valley [6]) and extensive faulting (e.g.
horst/graben structures). The valleys (grabens) are partially filled with sediment and sometimes
lakes. The largest, Lake Manly, filled Death Valley from 240,000 to 10,000 years BP [7].
DVRFS faults are thought to control groundwater flow to thousands of m-depth and over
hundreds of km; from montane recharge areas to large-discharge springs on the low-elevation
valley floors. This “interbasin flow” concept [8-11] is controversial [12-14] and a better
understanding of fault structure would enable improved predictions of the amount, age, and flow
paths of regional groundwater. As a result of societal pressures for water, the potential for
contamination migration from underground nuclear weapons testing on the Nevada National
Security Site (NNSS) and a proposed nuclear repository (Yucca Mountain), the deep regional
hydrology of the DVRFS is possibly the best understood in the world, and 3-D groundwater flow
models of ever-increasing sophistication are being developed by the US Geological Survey
(USGS) and Department of Energy (USDOE). Most significantly, a comprehensive DVRFS
hydrologic model with 1,500 m grid cell spacing (194 rows, 160 columns and 16 layers, surface
to 6 km below sea level) is being developed by the USGS. This model incorporates several
embedded models, including the 50-m-resolution Southern Amargosa eMbedded Model
(SAMM), which specifically covers the main area targeted in this proposal.
What is Known - Deep Life): To date, fluids from ~sixty-five DVRFS wells (100 – 1300 m)
and regional springs have been analyzed for aqueous geochemistry and microbial community
structure by our laboratory using next-gen and PCR-amplified 16s rRNA gene libraries.
Microbial communities, consistent with subsurface origins [15-17], have been detected in most
(e.g. the “dry hole” scenario is unlikely). Results have confirmed dissolved oxygen penetration to
> 1300 m depth in the DVRFS recharge zone [16, 18, 19] and microbial populations dominated
by proteobacteria and Thaumarchaeaota. Suboxic/anoxic wells sample deeper, hotter sources,
dominated by Nitrospirae, Firmicutes, and methanogens (Eurychaeaota). “Dark matter” phyla
(e.g. OP3) and sequences closely related to Candidatus Desulforudis audaviator are also
common (the bacterial population in 880-m-deep well BLM-1 (see below), for example, is ~50%
C. Desulforudis spp.). Our culture collection features sulfate-reducing and peptide-utilizing
Firmicutes related to Desulfotomaculum and C. D. audaxviator (~ 91% identity).
Proposed Sites: Our group has developed valuable professional contacts over the past decade
that support consideration of dozens of relevant sites. We a proposing three for evaluation:
1) Amargosa Valley, NV. Private quarry lands with existing drill pads enable permit-free
access to the “Gravity Fault”, which controls discharge of deep regional aquifer water to
Ash Meadows springs and Devils Hole (home to endangered species, e.g. Devils Hole
Pupfish). The fault may (or may not) protect these treasures from proposed groundwater
mining. Other sites, accessing the Lower Carbonate Aquifer (“LCA”, BLM-1 area), boast
existing drill pads and a relatively streamlined BLM permitting process.
2) Oasis Valley, NV (Spicer Ranch). Private lands enable permit-free access to DVRFS
recharge zone volcanic strata and probably very deep underlying Paleozoic carbonates.
3) Death Valley, CA. Managed by the US National Park Service (NPS), permitting may
require several years, but drilling is feasible for the floor of Death Valley (e.g. ~ 2,800 m
of saline deposits [6]) and the seismically-active [20, 21] Furnace Creek Fault Zone,
where several drill pads already exist (e.g. Echo Canyon and the Nevares Spring Mound).
DCO and Deep Life Community (DLC) Goals: The proposed sites support DLC goals 1 and
2), characterization of the diversity and distribution of deep life as it relates to the carbon cycle
and interactions between deep life and carbon cycling on Earth. In particular, a better
understanding of deep life across the LCA and shallower aquifers will facilitate an understanding
of sources and sinks of organic C and resolution of a persistent 14C age-dating discrepancy (14C
DIC much older than 14C DOC (~30,000 y vs. ~3,000 y [22]). 2) Given a local geothermal
gradient of at least 33oC/km [23, 24] (BLM-1 produces anoxic 61oC water at 880 m depth, e.g. ~
40oC per km), zones enabling the determination of the environmental limits of deep life (e.g.
temperature, salinity) will be relatively easily accessed: the Death Valley salt pan, for example,
is largely halite and 120oC isotherm should be surpassed at << 3 km depth.
ICDP Criteria: Global Criterion: This is both the most arid and fastest-growing region of North
America. This juxtaposition of factors must certainly represent a “world class problem”.
International Criterion: Our proposed study sites inform a range of geologically-important
provinces and rock types (e.g. continental dolomite, extrusive igneous). Need for Drilling: The
geology and hydrology of this region is controlled by faults, the most important of which are
invariably obscured by valley fill. One controversial topic involves whether or not the Death
Valley Salt Pan receives DVRFS flow. Drilling is the only means to test geophysical data. The
drilling of hazardous zones (e.g. active faults) is a current priority of ICDP. Depth and
Cost/Societal Needs: The USGS, NPS, and DOE are currently in discussions concerning a new
drilling project that would explore the Furnace Creek Fault Zone. It is conceivable that these
agencies would welcome new partners. High temperatures occur at shallow depths across the
DVRFS, reducing the cost of drilling to the “biotic fringe”. Contractors with relevant expertise
have been working in the basin for decades. Active Processes Criterion: See Geological Context.
Supplement: Responses to Suggested Workshop Priorities.
Potential for abiogenic H2: Deep sites from this system have already been characterized for H2
and it is measurable in anoxic sites (<0.01 vol%). In addition, aside from manmade
contamination, which produces large amounts of H2 via activity of up to 10s of millions of pCi/L
tritium, at least some uncontaminated wells have U concentrations exceeding the drinking water
MCL (e.g. ~15 pCi/L gross alpha) suggesting H2 production potential.
Potential to transect depth limit for life: Depending upon location, the 120oC Isotherm is
within reach of common drilling technology across portions of the DVRFS. The Geothermal
gradient in the Death Valley region is known to be very high, (e.g. published values of about
33oC/km [23, 24]). This gradient will likely be even higher on the floor of Death Valley.
Previously unexplored but globally important subsurface environment: Continental
carbonate rocks make up about 20% of the Earth’s land surface [25]. The proposed sites enable
the exploration of a wide range of rock types with shared hydrologic context (e.g. volcanics,
metamorphic, and sedimentary rocks in the same hole).
Potential for other disciplines (i.e. geophysics, hydrology, geology) to piggy-back onto our
project: Essentially all of the work conducted within the Death Valley Flow System to date has
been supported by these disciplines. Microbiology is the fresh face here. Numerous discussions
with workers in these disciplines indicate a very high degree of interest in partnering.
3D structure and hydrology: The geologic structure and hydrology of the proposed region is
among the best understood of any in the world (Wayne Belcher, USGS, pers. comm.). DVRFS 3
dimensional hydrologic models are extremely detailed, ground-truthed, and extend to great
depths (6 – 10 km below sea level). This factor may represent the greatest advantage embodied
by these sites.
The microbially pristine nature of the site, Although extensive drilling has been conducted,
very few of the wells within the regional flow system have been use for production. Other
activities, such as hydrocarbon production, have not occurred. Outside of urban areas, the region
is mostly unsettled and Las Vegas is in a different hydrologic basin and gets almost all of its
water from the Colorado River. There is no significant mining that impacts the regional flow
system. Although large amounts of radiologic contamination are present on the NNSS, none is
anywhere near the proposed sampling areas and DOE’S Underground Test Area Program
(UGTA) models predict that this contamination will not reach these zones for 100s of years.
Long-term accessibility to the borehole(s) afterwards for groundwater sampling and in situ
experiments. The precedent of hundreds of monitoring wells already existing on the NNSS and
elsewhere bode well in this regard. Well BLM-1 is already established as a long-term science
well by its stewards (Inyo Co, CA and the NPS) and long-term microbial substrate incubations
already underway by NASA Astrobiology Institute.
Potential Proponents (confirmed interest): Richard Friese, Hydrologist, Death Valley National
Park; Wayne Belcher and John Wilson , US Geological Survey, Las Vegas; Michael King, the
Hydrodynamics Group, LLC, Redmond, WA. Levi Kryder, Nye County Nuclear Waste
Repository Program Office, Pahrump, NV.
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