@article{BlisniukSternChamberlainetal.2005, author = {Blisniuk, Peter Michael and Stern, L. A. and Chamberlain, C. Page and Idleman, B. and Zeitler, P. K.}, title = {Climatic and ecologic changes during Miocene surface uplift in the Southern Patagonian Andes}, year = {2005}, abstract = {The up to similar to4 km high southern Patagonian Andes form a pronounced topographic barrier to atmospheric circulation in the southern hemisphere westerlies, and cause one of the most drastic orographic rain shadows on earth. Geologic data imply that this climatic pattern has been established or significantly enhanced during Miocene surface uplift of this Andean segment. We report evidence for important climatic and ecologic changes in the eastern foreland of the Patagonian Andes that appear to be the result of this uplift. To provide constraints on Miocene plant ecosystems and precipitation in the eastern (leeward) foreland of the Patagonian Andes, we determined carbon and oxygen isotope values of pedogenic carbonate nodules from a similar to500 m thick section of the continental Santa Cruz Formation. The age of these deposits was constrained by Ar/Ar dating of intercalated tuffs, which range from similar to22 to 14 Ma. At similar to16.5 Ma, the delta(13)C values increase by similar to3parts per thousand, the delta(18)O values decrease by >2parts per thousand, and the scatter in the oxygen isotope data increases significantly. We interpret these changes as the consequence of >1 km surface uplift in this Andean segment (from the delta(18)O values), and increased aridity to its east (from the delta(13)C values and the increased scatter in the delta(18)O values). Sediments overlying the Santa Cruz Formation are very limited in extent and volume, and dominated by coarse conglomerates related to Pleistocene and older glaciations. It thus seems that, by similar to14 Ma, deposition in the eastern foreland of the Southern Patagonian Andes had essentially ceased as the result of rain shadow formation. (C) 2004 Elsevier B.V. All rights reserved}, language = {en} } @article{HilleyBlisniukStrecker2005, author = {Hilley, G. E. and Blisniuk, Peter Michael and Strecker, Manfred}, title = {Mechanics and erosion of basement-cored uplift provinces}, year = {2005}, abstract = {Basement-cored uplift provinces are often characterized by high-angle reverse faulting along preexisting crustal heterogeneities, which may greatly affect the mechanics of deformation and the coupling between erosion and orogenic structure. Herein we construct a coupled deformation-erosion model to understand the mechanics and erosion of mountain belts in which the spatial distribution of deformation is largely influenced by the presence of preexisting high-angle faults. In this case, deformation is accommodated along, and topography is built above, these structures. This topographic loading leads to increasing lithostatic stresses beneath these regions. As a result, active deformation may migrate to frictionally stronger structures in adjacent regions where lithostatic loading is lower. The migration of deformation to such nearby structures depends on the Hubbert-Rubey pore fluid pressure ratio of the crust (lambda), the orientations of the frictionally weaker and stronger preexisting faults (beta(1) and beta(2), respectively), the friction coefficients (mu(b1) and mu(b2)) and Hubbert-Rubey fluid-pressure ratios (lambda(b1) and lambda(b2)) of these faults, and the surface slope of the topography above the frictionally weaker structure (alpha), assuming zero surface slope above the frictionally stronger structure. In general, we found that for a given alpha and beta(1), as mu(b1) increases lambda=lambda(b1)=lambda(b2) increases, and beta(2) decreases, the value of mu(b2) required to force deformation to migrate increases. However, as erosional processes lead to decreasing surface slopes, deformation will be inhibited from migrating to frictionally stronger structures in adjacent regions. Our model results may help to explain some aspects of the deformation observed and the possible correlation between precipitation and the migration of deformation within these tectonic provinces}, language = {en} } @article{BlisniukStern2005, author = {Blisniuk, Peter Michael and Stern, L. A.}, title = {Stable isotope paleoaltimetry : a critical review}, year = {2005}, abstract = {Stable isotope paleoaltimetry makes use of systematic trends in the distribution and isotopic composition of modern precipitation with climate and topography, and of the potential to estimate the isotopic composition of paleoprecipitation from authigenic (in-situ formed) minerals. To illustrate the usefulness as well as potential limitations of this method, we review (1) processes controlling the isotopic composition of modem precipitation, (2) stable isotope data from modern precipitation across regions of high topography, and (3) stable isotope data from authigenic minerals that have been used to infer paleotopography. From this we conclude that stable isotope studies of authigenic minerals can permit useful inferences on paleotopography, with uncertainties that critically depend on a detailed understanding of local- to global-scale paleoclimate during the time interval of interest}, language = {en} }