Pollen analysis of sediments from core BL96-2 at Bear Lake (42°N, 111°20′W), located on the Utah-Idaho border in America’s western cordillera, provides a record of regional vegetation changes from full glacial to the late Holocene. The reconstructed vegetation records are mostly independent of Bear Lake’s hydrologic state and are therefore useful for identifying times when climate forcing contributed to lake changes. The Bear Lake pollen results indicate that significant changes in the Bear Lake vegetation occurred during the intervals 15,300–13,900, 12,000–10,000, 7500–6700, 6700–5300, 3800–3600, and 2200–1300 cal yr B.P. These intervals coincide with regional shifts in vegetation and climate, documented in pollen, isotope and biogeographic records in the Basin and Range region, suggesting that large-scale climate was the primary forcing factor for these intervals of change. Maximum aridity and warmth is indicated from 12,000 to 7500 cal yr B.P., followed by intervals of generally more mesic and cool conditions, especially after 7500 cal yr B.P.

The stratigraphic and regional distributions of paleosol morphology in latest Pennsylvanian through Early Permian strata in Colorado, Utah, Arizona, New Mexico, Texas, and Oklahoma are presented in this paper. This regional extent corresponds to a paleolatitudinal gradient spanning ~5°S to 10°N. Morphological trends from this region delineate significant and systematic temporal and spatial changes in Permian-Carboniferous paleoenvironment and paleoclimate. The inferred latest Pennsylvanian (Virgilian) through early Early Permian environmental pattern is complex, but it indicates persistently dry, semiarid to arid conditions in Colorado, Utah, and Arizona, at paleolatitudes north of ~2°N, whereas lower paleolatitude (~2°S to 2°N) tropical regions in New Mexico exhibit a stepwise shift from subhumid to semiarid and variably seasonal conditions throughout late Pennsylvanian and the first half of Early Permian (Virgilian through Wolfcampian) time, followed by a subsequent shift to more arid conditions during the latter part of the Early Permian (Leonardian). Notably, strata from the southernmost paleosites, in Texas and Oklahoma, exhibit the most significant and abrupt climate changes through this period; they show a rapid transition from nearly ever-wet latest Pennsylvanian climate (at ~5°S) to drier and seasonal climate across the Permian-Carboniferous system boundary, and finally to arid and seasonal climate by Leonardian time (at ~2–4°N). The inferred climate patterns show no robust long-term correlation with the high-latitude Gondwanan records of glaciation. Rather, the long-term record of Permian-Pennsylvanian climate indicators from the southwestern United States is most simply explained by an ~8° northward tectonic drift through (essentially) static climate zones over western tropical Pangea during the interval of study. However, the relatively rapid perturbations to climate recorded by these pedogenic archives appear to be too rapid for tectonic forces and might correspond to changes in climate drivers, such as atmospheric p CO 2 , atmospheric circulation, and glacial-interglacial cycles.

During the Middle and Upper Miocene, calcrete and associated palustrine deposits formed marginal fringes adjacent to the margins of the Aranda–Burgo de Osma corridor in the southeastern Tertiary Duero basin. These environments interfingered laterally with narrow peripheral alluvial fans toward the corridor margins, whereas toward the center of the corridor, they graded into the fluvial systems transverse to the alluvial fans. Over time, the peripheral carbonate environments were replaced by fluvial systems. The calcretes form profiles with nodular grading upward to massive horizons. These profiles may be vertically stacked at the edges of the carbonate bodies. These calcretes are the product of mixed pedogenic and phreatic processes associated with the palustrine environments. Palustrine limestones were deposited in a shallow carbonate-precipitating lake that had low gradient margins and was subjected to periodic fluctuations in level. The sedimentologic characteristics of the carbonate facies indicate accumulation in a semiarid climate and conditions of scarce clastic sediment supply, which favored the development of carbonate-precipitating fringes. In contrast, their absence in parts of the sequence may have resulted from an increase in clastic sediment supply associated with a climatic change toward more humid conditions. At these times, the fluvial channels had greater lateral mobility and spread toward the corridor flanks, replacing the carbonate environments. Subsidence was greater in the central corridor than at its margins and did not change significantly during the Miocene. Thus, changes in climate and the clastic sediment input on the flanks of the Aranda–Burgo de Osma corridor were the main controls on the development of 10–20-m-thick carbonate clastic sediment sequences. Durante el Mioceno medio y superior en los márgenes del corredor de Aranda-Burgo de Osma, sureste de la cuenca del Duero, se desarrollaron franjas de depósitos palustres, rodeados de niveles de caliche. Estos términos carbonatados cambian lateralmente a depósitos de abanicos aluviales enraizados en los relieves que flanquean el corredor, mientras que hacia el centro del mismo pasan a los depósitos del sistema fluvial axial que drenaba esta región hacia el centro de la cuenca, situado más al oeste. Temporalmente los caliches y medios palustres eran substituidos por el sistema fluvial. Los caliches forman perfiles constituidos por niveles nodulares en la base que pasan a masivos hacia el techo, los cuales pueden llegar a apilarse formando secuencias compuestas en los márgenes de las unidades carbonatadas. Los caliches se forman debido a la acción combinada de procesos edáficos y freáticos, asociados a los medios palustres adyacentes. Estos últimos representan una sedimentación carbonatada lacustre en lagos muy someros, de baja pendiente, y afectados por exposiciones subaéreas frecuentes. Las características sedimentológicas de las facies carbonatadas indican una acumulación en condiciones semiáridas que favorecían un escaso suministro de material terrígeno a la cuenca y el desarrollo de facies carbonatadas en sus márgenes. Por el contrario, la expansión del sistema fluvial axial hacia estas áreas estaba propiciada por un aumento del suministro terrígeno como respuesta a condiciones climáticas más húmedas. En estos periodos el sistema fluvial axial se extendía hasta los márgenes del corredor, reemplazando los medios palustres y anulando en buena medida el desarrollo de los caliches asociados. La subsidencia era mayor en el corredor central que en sus márgenes y no cambió substancialmente durante el Mioceno. Los cambios en el clima y el suministro de materiales terrígenos en los flancos del corredor fueron los controles principales en la acumulación de ciclos carbonatado-terrígenos.