Cryptoendolithic cyanobacteria from calcite marble rock ridges, Taylor Valley, Antarctica

To study the influence of earthquakes and engineering disturbances on the deformation of deeply buried rock masses, shear tests were carried out on anchored sandstone rock masses, anchored marble rock masses, and anchored granite rock masses under creep fatigue loading, and a new creep fatigue model was established to characterize the deformation characteristics of anchored rock masses under creep fatigue loading. The creep fatigue curves of different lithologies clearly show three stages: creep attenuation, steady-state creep, and accelerated creep. Fatigue loading can increase the creep of anchored specimens, and the lower the rock strength is, the higher the creep variable under fatigue loading is. However, for the same rock strength, with the increase in load level, the creep variable produced by creep fatigue load presents a linear downward trend. Considering the changes in the mechanical properties of the anchored rock mass under creep fatigue loading, the creep fatigue model of anchored rock masses is established by introducing a function of the fatigue shear modulus, and the accuracy and applicability of the model are verified by laboratory creep fatigue test data. The model provides a theoretical basis for the study of anchored rock mass support under low-frequency earthquakes or blasting loads.

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Gravity constraints on structure of the East-West Antarctic lithospheric transition zone

10.26686/wgtn.15110442.v1 ◽

2021 ◽

Author(s):

Sam Treweek

Keyword(s):

Transition Zone ◽

Upper Mantle ◽

Geophysical Methods ◽

East Antarctica ◽

Gravity Models ◽

West Antarctica ◽

Asthenospheric Mantle ◽

Surface Uplift ◽

Mantle Viscosity ◽

Taylor Valley

The differing structural evolution of cratonic East Antarctica and younger West Antarctica has resulted in contrasting lithospheric and asthenospheric mantle viscosities between the two regions. Combined with poor constraints on the upper mantle viscosity structure of the continent, estimates of surface uplift in Antarctica predicted from models of glacial isostatic adjustment (GIA) and observed by Global Satellite Navigation System (GNSS) contain large misfits. This thesis presents a gravity study ofthe lithospheric transition zone beneath the Taylor Valley, Antarctica, conducted to constrain the variation in lithological parameters such as viscosity and density of the upper mantle across this region. During this study 119 new gravity observations were collected in the ice-free regions of the Taylor Valley and amalgamated with 154 existing land-based gravity observations, analysed alongside aerogravity measurements of southern Victoria Land. Gravity data are used to construct 2D gravity models of the subsurface beneath this region. An eastward gradient in Bouguer anomalies of ~- 1.6 mGal/km is observed within the Taylor Valley. Models reveal thickening of the Moho from 23±5 km beneath the Ross Sea to 35±5 km in the Polar Plateau (dipping at 24.5±7.2°), and lithospheric mantle 100 km thicker in East Antarctica (~200±30 km) than West Antarctica (~90±30 km). Models of predicted surface uplift history are used to estimate an asthenospheric mantle viscosity of 2.1x1020 Pa.s at full surface recovery beneath the Ross Embayment, differing by ~14% from the viscosity at 50% recovery. The temperature contrast between lithospheric and asthenospheric mantle is estimated as ~400°C, equivalent to a viscosity that decreases by a factor of about 30 over the mantle boundary. Results demonstrate that the history of surface uplift in the study area may be complicated, resulting in observations of uplift, or subsidence, at GNSS stations. Future work should incorporate additional geophysical methods, such as seismicity and electrical resistivity, improving constraints on gravity models. A better understanding of the surface uplift (or subsidence) history in the Transantarctic Mountains is critical, with implications in reducing uncertainty in GIA models.

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Glacier mass balances (1993–2001), Taylor Valley, McMurdo Dry Valleys, Antarctica

Journal of Glaciology ◽

10.3189/172756506781828511 ◽

2006 ◽

Vol 52 (178) ◽

pp. 451-462 ◽

Cited By ~ 43

Author(s):

Andrew G. Fountain ◽

Thomas H. Nylen ◽

Karen L. MacClune ◽

Gayle L. Dana

Keyword(s):

Mass Balance ◽

Piecewise Linear ◽

Objective Assessment ◽

Mcmurdo Dry Valleys ◽

Dry Valleys ◽

Mass Balances ◽

Missing Measurements ◽

Wind Speeds ◽

Taylor Valley ◽

Air Temperatures

AbstractMass balances were measured on four glaciers in Taylor Valley, Antarctica, from 1993 to 2001. We used a piecewise linear regression, which provided an objective assessment of error, to estimate the mass balance with elevation. Missing measurements were estimated from linear regressions between points and showed a significant improvement over other methods. Unlike temperate glaciers the accumulation zone of these polar glaciers accumulates mass in summer and winter and the ablation zone loses mass in both seasons. A strong spatial trend of smaller mass-balance values with distance inland (r2 = 0.80) reflects a climatic gradient to warmer air temperatures, faster wind speeds and less precipitation. Annual and seasonal mass-balance values range only several tens of millimeters in magnitude and no temporal trend is evident. The glaciers of Taylor Valley, and probably the entire McMurdo Dry Valleys, are in equilibrium with the current climate, and contrast with glacier trends elsewhere on the Antarctic Peninsula and in temperate latitudes.

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Botryomyces caespitosus. [Descriptions of Fungi and Bacteria].

IMI Descriptions of Fungi and Bacteria ◽

10.1079/dfb/20056401551 ◽

2003 ◽

Author(s):

E. V. Bogomolova

Keyword(s):

Renal Failure ◽

Geographical Distribution ◽

Homo Sapiens ◽

Skin Lesions ◽

Domestic Animals ◽

Rock Surface ◽

Immunocompromised Patients ◽

Prolonged Contact ◽

Marble Rock ◽

Archaeological Objects

Abstract A description is provided for Botryomyces caespitosus. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Human dermatomycosis (mycoses); cutaneous phaeohyphomycosis; mycotic granuloma - skin lesions on arms and legs; usually in immunocompromised patients, or in patients with chronic renal failure, transplants and immunosuppressive therapy. The fungus also inhabits cracks in marble, where it may be implicated in degradation of the surface, a possible factor in the biodeterioration of sculptures and archaeological objects. HOSTS: Homo sapiens, marble (rock surface). GEOGRAPHICAL DISTRIBUTION: EUROPE: Italy, Spain, Ukraine. TRANSMISSION: In humans by traumatic inoculation; sometimes through prolonged contact with domestic animals; otherwise, presumably air-borne dissemination of propagules.

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