Paleogene landscape evolution of the central North American Cordillera: Developing topography and hydrology in the Laramide foreland

Abstract

Isotopic and elemental records of authigenic calcite from lacustrine deposits in the intraforeland basins of Utah were analyzed in an effort to reconstruct the regional paleoclimate, paleohydrology, and paleotopography of the early Cenozoic central North American Cordillera. Isotopic profi les for Paleogene Lakes Uinta, Flagstaff, and Claron show relatively large oxygen isotopic shifts that are diachronous among basins with an ~7‰ decrease in δ 18O calcite values at ca. 45 Ma in Lake Flagstaff, an ~5‰ decrease in δ 18O calcite values between ca. 42 and 35 Ma in Lake Claron, and an ~6‰ decrease in δ 18O calcite values between ca. 44 and 43 Ma in Lake Uinta. We interpret these negative oxygen isotopic shifts to be the combined result of increased hypsometric mean elevation of basin catchments and related freshening associated with basin infi lling. The basins studied also have undergone periods of intense evaporation during periods of hydrologic closure, which, for example, produced an ~7‰ increase in δ 18O calcite values in Lake Uinta beginning at ca. 51 Ma. Hydrologic closure in the Uinta Basin probably resulted from growth of local topography that diverted previously substantial infl ows from low elevation regions within the foreland.This study adds to the growing body of evidence that suggests a pattern of alongstrike variations in the timing of topographic development and dissection of the Cordilleran landscape during the early Cenozoic. We favor an interpretation that calls for the middle Eocene rearrangement of regional drainage patterns such that intraforeland basins that once received waters from far-fl ung foreland river systems became dominated by infl ows of low δ 18O waters from catchments with higher hypsometric mean elevations that drained the adjacent hinterland and/or basin-bounding uplifts. This drainage reorganization is analogous but subsequent to the large-scale integration of catchments in the northern Cordillera that has been recognized on the basis of isotopic and sedimentological evidence in Montana and Idaho at ca. 50-47 Ma, with rivers fl owing southeast into Lake Gosiute at ca. 49 Ma and then for a time reaching Lake Uinta, causing a prominent highstand in that lake at 48.6 Ma. The negative oxygen isotopic shifts presented herein, which occurred between ca. 45 and ca. 35 Ma in the intraforeland basins of Utah, may refl ect the north-to-south progression of drainage integration in the Cordillera as magmatism and related topography swept southward through the hinterland and increased the hypsometric mean of catchments that fed subjacent intraforeland basins.

Stable isotope-based reconstruction of Oligo-Miocene paleoenvironment and paleohydrology of Central Anatolian lake basins (Turkey)

“…Evaporation, itself governed by temperature and relative humidity, strongly controls the depletion in the light oxygen isotope 16 O in the water phase. Changes in temperature, rainfall sources, riverine influx, and groundwater input are retained in the oxygen isotope ratios of carbonates (δ 18 O carb ) which precipitate from lake water (e.g., Turner et al 1983;Talbot 1990;Teranes et al 1999;Lamb et al 2000;Schwalb & Dean 2002;Leng & Marshall 2004;Yansa et al 2007;Davis et al 2009;Deocampo 2010;Kent-Corson et al 2010 (Leng & Marshall 2004). Lacustrine carbonate oxygen isotope records have been also used in isotopebased paleoelevation models exploiting the systematic relationship between oxygen isotopes in precipitation and surface elevation (e.g., Currie et al 2005;Garzione et al 2008;Mix et al 2011;Campani et al 2012).…”

The Great Basin Altiplano during the middle Cenozoic ignimbrite flareup: insights from volcanic rocks

“…Kent-Corson et al (2006) conclude there is a growing body of evidence for a migration of high surface elevation from the northern to the southern Great Basin from the late Eocene to the Miocene. They relate this phenomenon to the southward rollback of the subducting slab and upwelling of hotter and expanding asthenosphere beneath the continental lithosphere (Davis et al 2009). …”

The Cenozoic climatic and topographic evolution of the western North American Cordillera

“…This decrease is a result of changes in rainout and decreasing temperature with latitude. Since the bulk of the study area has been at nearly the same latitude for the Cenozoic (Smith and others, 1981) (Kent-Corson and others, 2006;Carroll and others, 2008;Smith and others, 2008;Davis, 2009aDavis, , 2009bDoebbert and others, 2010 (Smith and others, 1993;Wang and others, 1993;Mack and others, 1994;Fox and Koch, 2004;Horton and others, 2004;Kent-Corson and others, 2006;Horton and Chamberlain, 2006;Fan and others, 2011; this study), paleolake sediments (Rogers and others, 1992;Poulson and John, 2003;Davis and others, 2008Davis and others, , 2009aDavis and others, , 2009b; this study) and fossil bivalves (Fan and Dettman, 2009); squares represent smectite from weathered ashes (Poage and Chamberlain, 2002;Takeuchi and Larson, 2005;Sjostrom and others, 2006); diamonds represent hydrated glasses from volcanic ashes (Mulch and others, 2008;Cassel and others, 2009b); triangles represent kaolinite from weathered stream deposits (Mulch and others, 2006); and pentagons are muscovite from shear zones others, 2004, 2007 documented for southern British Columbia (Mulch and others, 2004;Greenwood and others, 2005;Tribe, 2005;Mulch and others, 2007 18 O values of surface waters east of the Washington Cascades were higher than they are today. Third, the isotopic rain shadow on the east side of the Sierra Nevada had been established by the mid-Miocene and the isotopic values there were similar to modern values.…”