Landscape evolution and preservation of ice over one million years old quantified with cosmogenic nuclides 26Al, 10Be, and 21Ne, Ong Valley, Antarctica

Antarctica has been glaciated for the past 35-40 million years (Denton et al., 1991) and evidence of periodic fluctuations of the Antarctic ice sheet (AIS) during the Cenozoic are recorded in the ice sheet itself, deep sea sediments, and glacial deposits on the continent (Ingólfsson, 2004). Quaternary continental records of AIS extent is limited to few locations along the Transantarctic Mountains (TAM) and coastal continental boundaries (Denton et al., 1984; Denton et al., 1989). Records of atmospheric variation over time, glacial extents, and ice sheet responses to environmental changes are required to understand modern day forces on climate and the environment and provide a context in which to relate modern observations to the past. In this framework, this paper evaluates the geomorphic stability of Ong Valley within the Central Transantarctic Mountains (CTM) and the preservation of Pleistocene aged ice underneath an insulating lag deposit. Ong Valley in the Central Transantarctic Mountains (CTM) contains ancient buried glacier ice derived from past flow of the adjacent Argosy Glacier. The valley floor is covered with patterned ground and has three distinct glacial tills. Geomorphic and stratigraphic evidence shows that these deposits originate from sublimation of debris-laden glacier ice. Buried glacier ice is still present beneath the youngest two drifts, one of which is older than one million years. The tills above the ice record the repeated advances and stagnations of the Argosy Glacier. Cosmogenic exposure age dating of these tills provides ages, ice sublimation rates and regolith erosion rates that support the antiquity of the ice below. The oldest ice on Earth has an undisputed age of 800 Kya and is at the bottom of large ice sheets (Fischer et al., 2013). Access to it requires extensive drilling through kilometers of ice. Conversely, the ice in Ong valley is preserved beneath only 1 m of till and is over 1 million years old. Geomorphically similar ice was found in Beacon Valley, but its age (~8.1 Mya) was inferred from dating of volcanic ash above the ice (Sugden et al., 1995). Subsequent analysis from other investigators suggest that the age of the ash may not be a good indicator for the age of the ice below it (Hindmarsh et al., 1998; Ng et al., 2005; Stone et al., 2000). Concentrations of cosmogenic 10Be, 26Al, and 21Ne were measured in regolith samples collected every ~10 cm in 1 m deep vertical transects through three tills in Ong Valley. Transects reach the buried ice surface in the two younger tills. Cosmogenic-nuclide concentrations in these transects are functions of: i) the age of the till and ice below it; ii) the rate of formation of the till by sublimation of underlying ice; and iii) the rate of surface erosion of the till. In general, a young till unit will have 26Al and 10Be concentrations that are primarily a function of till age; however, over time, 26Al and 10Be concentrations reach equilibrium with erosion, sublimation rates, and radioactive decay; thus, 26Al and 10Be concentrations in older tills primarily provide information about those rates. Conversely, stable nuclide 21Ne only accumulates over time which makes it useful in determining the age of older tills where as 26Al and 10Be provide minimum limiting ages. 26Al, 10Be, and 21Ne measurements in Ong Valley are consistent with a scenario in which tills are derived from progressive sublimation of glacial ice containing 10% by volume englacial debris. 26Al and 10Be concentrations in the youngest till constrain its emplacement age at 18.4 Kya. 21Ne nuclide concentrations in the two oldest tills are best explained by ice sublimation rates on the order of tens of m/Mya and surface erosion rates of the till on the order of m/Mya for at least 0.9 Mya to 1.5 Mya. Concentrations of nuclides in the bottom of the second drift suggest that local sublimation rates have increased slightly in the past 40-150 Kya. These observations imply that the ice below the middle drift is the oldest undisturbed glacier ice currently known on Earth and should provide ancient atmospheric records within one meter of Earth’s surface

Telomeres and Telomerase. Ciba Foundation Symposium 211

1999 Cancer Research Campaig

Increase in type A virus particles induced in BALB/c mouse epidermis during chemical carcinogenesis.

Electron microscopic observations of normal BALB/c mouse epidermis revealed the presence of isolated intracisternal A particles. Hyperplasia, papilloma and carcinoma formation induced by topical application of the carcinogenic polycyclic hydrocarbons benz(a)pyrene (B(a)P) and 3-methylcholanthrene (MC) is accompanied by an increase in the mumber of A particles. Topical application of a non-carcinogenic irritant alpha-pinene (alpha P) failed to provide comparable changes. Examination of the nuclei indicated occasional electron dense granules in the nucleoplasm which became more common throughout the progression of carcinogenesis

C-type and intracisternal A-type virus particles during epidermal carcinogenesis by tobacco smoke condensate in BALB/c mice.

Electron microscopic observations of sequential stages of skin carcinogenesis induced by tobacco smoke condensate (SC) and a cyclohexane fraction of tobacco smoke condensate (G) revealed an increase in incidence of intracisternal A particles within the epidermal cells. Tumours induced by SC also contained C-type particles, but these were not seen in G-induced tumours or after irritant or solvent treatment. There was no evidence of an increase in intracisternal A particles after irritant or solvent treatment. A direct relationship between the proliferation of A particles and neoplastic growth of BALB/c mouse epidermis appears likely. The data suggest possible activation of a latent C-type virus by SC

Geodynamic setting and origin of the Oman/UAE ophiolite

The ~500km-long mid-Cretaceous Semail nappe of the Sultanate of Oman and UAE (henceforth referred to as the Oman ophiolite) is the largest and best-preserved ophiolite complex known. It is of particular importance because it is generally believed to have an internal structure and composition closely comparable to that of crust formed at the present-day East Pacific Rise (EPR), making it our only known on-land analogue for ocean lithosphere formed at a fast spreading rate. On the basis of this assumption Oman has long played a pivotal role in guiding our conceptual understanding of fast-spreading ridge processes, as modern fast-spread ocean crust is largely inaccessible