Groundwater seeps in Taylor Valley Antarctica: an example of a subsurface melt event

2005 ◽  
Vol 40 ◽  
pp. 200-206 ◽  
Author(s):  
W. Berry Lyons ◽  
Kathleen A. Welch ◽  
Anne E. Carey ◽  
Peter T. Doran ◽  
Diana H. Wall ◽  
...  
Keyword(s):  
Austral Summer ◽  
Geochemical Data ◽  
Decadal Time Scale ◽  
Stream Flows ◽  
Unusual Event ◽  
The North ◽  
Taylor Valley ◽  
Dry Valley ◽  
Geochemical Models ◽  
Sources Of Solutes

AbstractThe 2001/02 austral summer was the warmest summer on record in Taylor Valley, Antarctica, (∼78° S) since continuous records of temperature began in 1985. The highest stream-flows ever recorded in the Onyx River, Wright Valley, were also recorded that year (the record goes back to the 1969/70 austral summer). In early January 2002, a groundwater seep was observed flowing in the southwest portion of Taylor Valley. This flow has been named ‘Wormherder Creek’ (WHC) and represents an unusual event, probably occurring on a decadal time-scale. The physical characteristics of this feature suggest that it may have flowed at other times in the past. Other groundwater seeps, emanating from the north-facing slope of Taylor Valley, were also observed. Little work has been done previously on these very ephemeral seeps, and the source of water is unknown. These features, resembling recently described features on Mars, represent the melting of subsurface ice. The Martian features have been interpreted as groundwater seeps. In this paper we compare the chemistry of the WHC groundwater seep to that of the surrounding streams that flow every austral summer. The total dissolved solids content of WHC was ∼6 times greater than that of some nearby streams. The Na : Cl and SO4 : Cl ratios of the seep waters are higher than those of the streams, but the Mg : Cl and HCO3 : Cl ratios are lower, indicating different sources of solutes to the seeps compared to the streams. The enrichment of Na and SO4 relative to Cl may suggest significant dissolution of mirabilite within the previously unwetted soil. The proposed occurrence of abundant mirabilite in higher-elevation soils of the dry valley region agrees with geochemical models developed, but not tested, in the late 1970s. The geochemical data demonstrate that these seeps could be important in ‘rinsing’ the soils by dissolving and redistributing the long-term accumulation of salts, and perhaps improving habitat suitability for soil biota. The H4SiO4 concentration is 2–3 times greater in WHC than in the surrounding streams, indicating a large silicate-weathering component in the seep waters.

Geochemistry of contrasting stream types, Taylor Valley, Antarctica

2020 ◽  
Vol 133 (1-2) ◽  
pp. 425-448
Author(s):  
Russell S. Harmon ◽  
Deborah L. Leslie ◽  
W. Berry Lyons ◽  
Kathleen A. Welch ◽  
Diane M. McKnight
Keyword(s):  
Dissolved Oxygen ◽  
Austral Summer ◽  
Mineral Dissolution ◽  
Silicate Mineral ◽  
Cation Composition ◽  
Taylor Valley ◽  
Low Concentrations ◽  
Hyporheic Zones ◽  
Dry Valley ◽  
Geochemical Fingerprint

Abstract The McMurdo Dry Valley region is the largest ice-free area of Antarctica. Ephemeral streams flow here during the austral summer, transporting glacial meltwater to perennially ice-covered, closed basin lakes. The chemistry of 24 Taylor Valley streams was examined over the two-decade period of monitoring from 1993 to 2014, and the geochemical behavior of two streams of contrasting physical and biological character was monitored across the seven weeks of the 2010–2011 flow season. Four species dominate stream solute budgets: HCO3–, Ca2+, Na+, and Cl–, with SO42–, Mg2+, and K+ present in significantly lesser proportions. All streams contain dissolved silica at low concentrations. Across Taylor Valley, streams are characterized by their consistent anionic geochemical fingerprint of HCO3 > Cl > SO4, but there is a split in cation composition between 14 streams with Ca > Na > Mg > K and 10 streams with Na > Ca > Mg > K. Andersen Creek is a first-order proglacial stream representative of the 13 short streams that flow <1.5 km from source to gage. Von Guerard is representative of 11 long streams 2–7 km in length characterized by extensive hyporheic zones. Both streams exhibit a strong daily cycle for solute load, temperature, dissolved oxygen, and pH, which vary in proportion to discharge. A well-expressed diurnal co-variation of pH with dissolved oxygen is observed for both streams that reflects different types of biological control. The relative consistency of Von Guerard composition over the summer flow season reflects chemostatic regulation, where water in transient storage introduced during times of high streamflow has an extended opportunity for water-sediment interaction, silicate mineral dissolution, and pore-water exchange.

scholarly journals Diurnal chemistry of two contrasting stream types, Taylor Valley, McMurdo Dry Valley Region, Antarctica

2019 ◽  
Vol 98 ◽  
pp. 01020
Author(s):  
Russell S. Harmon ◽  
Deborah L. Leslie ◽  
W. Berry Lyons ◽  
Kathleen A. Welch ◽  
Diane M. McKnight
Keyword(s):  
Dissolved Oxygen ◽  
Hyporheic Zone ◽  
Austral Summer ◽  
Ephemeral Streams ◽  
Secondary Effects ◽  
Order Stream ◽  
Taylor Valley ◽  
Dry Valley ◽  
Direct Reflection ◽  
Algal Mat

Numerous ephemeral streams flow within the McMurdo Dry Valley Region of Antarctica that transport glacial meltwater to perennially ice-covered, closed-basin lakes during the austral summer. The diurnal behavior for two Taylor Valley streams of different character was examined during the summer of 2010-11. Andersen Creek is a short, 1st-order proglacial stream, whereas Von Guerard Stream is a long, high-order stream with an extensive hyporheic zone that has a substantial cyanobacterial algal mat community in its middle reaches. Both streams display strong daily cycles for temperature, electrical conductivity, dissolved oxygen, and pH. Conductivity varies in concert with flow, with solute dilution occurring during the daily high-flow pulse. Dissolved oxygen co-varies strongly with pH at Andersen Creek but not for Von Guerard Stream. Each stream has a distinct geochemical character that for Andersen Creek is a direct reflection of its glacial source, unmodified by secondary effects, whereas that for Von Guerard Stream is modulated by its resident algal mat community and through extensive hyporheic zone interaction and exchange.

scholarly journals The seasonal evolution of albedo across glaciers and the surrounding landscape of the Taylor Valley, Antarctica

2019 ◽  
Author(s):  
Anna Bergstrom ◽  
Michael Gooseff ◽  
Madeline Myers ◽  
Peter T. Doran
Keyword(s):  
Austral Summer ◽  
Short Wave ◽  
Desert Ecosystem ◽  
Dry Valleys ◽  
Seasonal Evolution ◽  
Taylor Valley ◽  
Incoming Radiation ◽  
Dry Valley ◽  
Summer Temperatures ◽  
Surrounding Landscape

Abstract. The McMurdo Dry Valleys (MDVs) of Antarctica are a polar desert ecosystem consisting of alpine glaciers, ice-covered lakes, streams, and expanses of vegetation-free rocky soil. Because average summer temperatures are close to 0 °C, glacier melt dynamics in particular, but the Dry Valley ecosystem in general, are closely linked to the energy balance. A slight increase in incoming radiation or change in albedo can have large effects on the timing and volume of melt water. However, we have yet to fully characterize the seasonal evolution or spatial variability of albedo in the valleys. In this study, we aim to understand the drivers of landscape albedo change within and across seasons. To do so, we used a camera, gps, and short wave radiometer from a helicopter-based platform to fly transects 4–5 times a season along Taylor Valley over three seasons. We coupled these data with incoming radiation measured at 6 meteorological stations distributed along the valley to calculate the distribution of albedo across individual glaciers, lakes, and the soil surfaces. We hypothesized that albedo would decrease throughout the austral summer with ablation of snow patches and ice and increasing sediment exposure on the glacier and lake surfaces. However, small snow events (

A Kinematic Reconstruction of Jurassic ocean spreading from the ophiolites of California, the western U.S. using structural geology and paleomagnetism.

2021 ◽  
Author(s):  
Cemil Arkula ◽  
Nalan Lom ◽  
John Wakabayashi ◽  
Grant Rea-Downing ◽  
Mark Dekkers ◽  
...  
Keyword(s):  
North America ◽  
Relative Position ◽  
North American ◽  
Fault System ◽  
Paleomagnetic Data ◽  
Geochemical Data ◽  
Ophiolite Belt ◽  
The North ◽  
Western Us ◽  
Jurassic Ophiolites

<p>The western edge of the North America plate contains geological records that formed during the long-lived convergence between plates of the Panthalassa Ocean and North America. The geology of different segments along western North America indicates different polarities (eastward and westward) for subducted slabs and thereby various tectonic histories and settings. The western United States (together with Mexico) plays a key role in this debate, many geologic interpretations assume continuous eastward subduction in contrast to observations within proximal geologic segments and tomographic images of the lower mantle below North America and the eastern Pacific Ocean which suggest a more complex subduction history. In this study, we aim to evaluate the plate tectonic setting in which the Jurassic ophiolites of California formed. Geochemical data from these ophiolites suggest that they formed above a nascent intra-oceanic or continental margin subduction zone. We first developed a kinematic reconstruction of the western US geology back to the Jurassic based on published structural geological data. Importantly, we update the reconstruction of the various branches of the San Andreas fault system to determine the relative position of the ophiolite fragments and adopt a previous restoration of Basin and Range extension which we expand northward towards Washington state. We then reconstruct North American margin deformation associated with Cretaceous to Paleogene shortening and strike-slip faulting. We find no clear candidates in the geological record that may have accommodated major subduction between the Jurassic ophiolite belt and the North American margin and consequently concur with the school of thought that considers that the ophiolite belt, as well as the underlying subduction-accretionary Franciscan Complex, likely formed in the North American fore-arc. We collected paleomagnetic data to reconstruct the spreading direction of the Jurassic Californian ophiolites, by providing new paleomagnetic data from sheeted dykes of the Josephine and Mt. Diablo Ophiolites. These suggest a NE-SW paleo-ridge orientation, oblique to the North American margin which may be explained by partitioning of a dextral component of subduction obliquity relative to North America. We used this spreading direction in combination with published ages of the ophiolites and our restoration of the relative position of these ophiolites prior to post-Jurassic deformation to construct a ridge-transform system at which the Jurassic ophiolites accreted. The results will be used to evaluate which parts of the subduction systems that existed in the eastern Panthalassa Ocean may reside in the western US, and which parts may be better sought in the northern Canadian Segment or/and in the southern Caribbean region.</p>

Durrington Walls: a Ceremonial Enclosure of the 2nd Millennium BC

Antiquity ◽  
1968 ◽  
Vol 42 (165) ◽  
pp. 20-26 ◽  
Author(s):  
G. J. Wainwright
Keyword(s):  
Land Surface ◽  
Outer Edge ◽  
The South ◽  
Double Row ◽  
Early 19Th Century ◽  
Radiocarbon Dates ◽  
Southern Sector ◽  
The North ◽  
Animal Bones ◽  
Dry Valley

Durrington Walls lies one quarter of a mile to the north of the outskirts of Amesbury in Wiltshire and 9 miles north of Salisbury (SU 150437). Stonehenge is situated 2 miles to the south-east and 80 yds. to the south of the enclosure is Woodhenge which was excavated by Mrs Cunnington in 1926-8. The much ploughed bank, which encloses a dry valley opening on to the River Avon, was initially recorded by Sir Richard Colt Hoare in the early 19th century (1812, 169), but until the recently completed series of excavations the only digging on the site was that carried out by Professor Stuart Piggott in 1952, despite recognition of the enclosure as being one of the largest henge monuments in the country. The 1952 excavations were in the nature of an exploration on both sides of a pipe trench where it intersected with the bank in its southern sector (Stone, Piggott and Booth, 1954). A double row of post-holes was recorded along the outer edge of the bank and a quantity of animal bones, flints and sherds of Grooved Ware was found on top of the old land surface which was preserved beneath it. Sherds of Grooved Ware and two small fragments of Beaker were recorded from domestic refuse overlying the bank talus. Radiocarbon dates of 2620± 40 and 2630 ± 70 BC were obtained from charcoal under the bank in its southern sector (Piggott, 1959, 289). These determinations were described by Professor Piggott as ‘archaeologically unacceptable’ as two small scraps of Beaker pottery were found in association with the abundant Grooved Ware.

Bronze Age Barrows on Charmy Down and Lansdown, Somerset

1950 ◽  
Vol 30 (1-2) ◽  
pp. 34-46 ◽  
Author(s):  
Audrey Williams
Keyword(s):  
Bronze Age ◽  
Iron Age ◽  
The South ◽  
Stream Flows ◽  
North East ◽  
The North

Charmy Down is a plateau three miles north-east of Bath (fig. 1, 1), east of the Bath-Tetbury road. About a square mile in extent it has a general height of well over 600 ft. To the north the scarp falls swiftly, on the east more gently, to the wooded valley of St. Catherine's Brook, a tributary of the Bristol Avon and the modern Somerset–Gloucester boundary. At the foot of the steep western scarp a second stream flows south to the Avon. On the south Chilcombe Bottom separates Charmy Down from Solsbury Hill, distinguished by its Iron Age earthwork. The underlying rock is oolite, a southward continuation of the Cotswold formation.

scholarly journals Volcanic record of the arc-to-rift transition onshore of the Guaymas basin in the Santa Rosalía area, Gulf of California, Baja California

Geosphere ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 1012-1041
Author(s):  
Cathy Busby ◽  
Alison Graettinger ◽  
Margarita López Martínez ◽  
Sarah Medynski ◽  
Tina Niemi ◽  
...  
Keyword(s):  
Gulf Of California ◽  
Baja California ◽  
Sedimentary Basin ◽  
Volcanic Rocks ◽  
Seafloor Spreading ◽  
Geochemical Data ◽  
Normal Faults ◽  
Guaymas Basin ◽  
The North ◽  
Santa Rosalia

Abstract The Gulf of California is an archetype of continental rupture through transtensional rifting, and exploitation of a thermally weakened arc to produce a rift. Volcanic rocks of central Baja California record the transition from calcalkaline arc magmatism, due to subduction of the Farallon plate (ca. 24–12 Ma), to rift magmatism, related to the opening of the Gulf of California (<12 Ma). In addition, a suite of postsubduction rocks (<12 Ma), referred to as “bajaites,” are enriched in light rare-earth and other incompatible elements (e.g., Ba and Sr). These are further subdivided into high-magnesian andesite (with 50%–58% SiO2 and MgO >4%) and adakite (>56% SiO2 and MgO <3%). The bajaites correlate spatially with a fossil slab imaged under central Baja and are inferred to record postsubduction melting of the slab and subduction-modified mantle by asthenospheric upwelling associated with rifting or slab breakoff. We report on volcanic rocks of all three suites, which surround and underlie the Santa Rosalía sedimentary rift basin. This area represents the western margin of the Guaymas basin, the most magmatically robust segment of the Gulf of California rift, where seafloor spreading occurred in isolation for 3–4 m.y. (starting at 6 Ma) before transtensional pull-apart basins to the north and south ruptured the continental crust. Outcrops of the Santa Rosalía area thus offer the opportunity to understand the magmatic evolution of the Guaymas rift, which has been the focus of numerous oceanographic expeditions. We describe 21 distinct volcanic and hypabyssal map units in the Santa Rosalía area, using field characteristics, petrographic data, and major- and trace-element geochemical data, as well as zircon isotopic data and ten new 40Ar-39Ar ages. Lithofacies include lavas and lava domes, block-and-ash-flow tuffs, ignimbrites, and hypabyssal intrusions (plugs, dikes, and peperites). Calcalkaline volcanic rocks (13.81–10.11 Ma) pass conformably upsection, with no time gap, into volcanic rocks with rift transitional chemistry (9.69–8.84 Ma). The onset of rifting was marked by explosive eruption of silicic ignimbrite (tuff of El Morro), possibly from a caldera, similar to the onset of rifting or accelerated rifting in other parts of the Gulf of California. Epsilon Hf zircon data are consistent with a rift transitional setting for the tuff of El Morro. Arc and rift volcanic rocks were then juxtaposed by normal faults and tilted eastward toward a north-south fault that lay offshore, likely related to the north-south normal faults documented for the early history of the Guaymas basin, prior to the onset of northwest-southeast transtenional faulting. Magmatism in the Santa Rosalía area resumed with emplacement of high-magnesian andesite lavas and intrusions, at 6.06 Ma ± 0.27 Ma, coeval with the onset of seafloor spreading in the Guaymas basin at ca. 6 Ma. The 9.69–8.84 Ma rift transitional volcanic rocks underlying the Santa Rosalía sedimentary basin provide a maximum age on its basal fill. Evaporites in the Santa Rosalía sedimentary basin formed on the margin of the Guaymas basin, where thicker evaporites formed. Overlying coarse-grained clastic sedimentary fill of the Santa Rosalía basin and its stratiform Cu-Co-Zn-Mn sulfides may have accumulated rapidly, coeval with emplacement of 6.06 Ma high-magnesian andesite intrusions and the ca. 6 Ma onset of seafloor spreading in the Guaymas basin.

scholarly journals Ice-Sheet flow in the Vicinity of Southern Victoria Land, Antarctica: Implications for Glacial Chronology

1979 ◽  
Vol 24 (90) ◽  
pp. 483
Author(s):  
David J. Drewry
Keyword(s):  
Ice Sheet ◽  
East Antarctica ◽  
Small Surface ◽  
The North ◽  
Ice Surface ◽  
Glacial Chronology ◽  
Victoria Land ◽  
Dry Valley ◽  
Radio Echo Sounding ◽  
Taylor Glacier

Abstract Systematic radio echo-sounding during three seasons since 1971–72 has produced data on the configuration of the ice sheet in East Antarctica. In the sector extending inland from southern Victoria Land, the ice sheet exhibits a large ridge which drives ice towards David Glacier in the north and Mulock and Byrd Glaciers to the south. Within 100 km of the McMurdo dry-valley region soundings along ten sub-parallel lines (c. 10 km apart) provides detail on ice surface and flow patterns at the ridge tip. A small surface dome lies just inland of Taylor Glacier. The surface drops by 100 m or more before rising to join the major ridge in East Antarctica.

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