Provenance of sediments deposited at paleolake San Felipe, western Sonora Desert: Implications to regimes of summer and winter precipitation during last 50 cal kyr BP (original) (raw)
Related papers
2011
A new geochemical record from the paaleolake Santiaguillo documents the hydrological variability of subtropical northern Mexico over the last ∼14 cal. ka. Summer-season runoff, lake water salinity and deposition of sediments by aeolian activity were reconstructed from concentrations of K, Ca and Zr/K in bulk sediments. More-than-average runoff during c. 12.3-9.3 cal. ka BP represented an interval of enhanced summer precipitation. Arid intervals of c. 14-12.3 cal. ka BP and c. 6-4.3 cal. ka BP were characterized by average and more-thanaverage aeolian activity. Comparison with proxy records of summer as well as winter precipitation from tropical and sub-tropical North America and sea surface temperatures from the Atlantic and Pacific provides insight into the source of moisture and possible forcing. The wet Pleistocene−Holocene transition and early Holocene was contemporary with warmer conditions in the Gulf of California. We suggest that the Atlantic had minimal influence on the summer precipitation of the western part of sub-tropical northern Mexico and that the source of moisture was dominantly Pacific.
Earth Surface Processes and Landforms, 2007
Sedimentological, compositional and geochemical determinations were carried out on 54 desert and coastal dune sand samples to study the provenance of desert and coastal dunes of the Altar Desert, Sonora, Mexico. Grain size distributions of the desert dune sands are influenced by the Colorado River Delta sediment supply and wind selectiveness. The desert dune sands are derived mainly from the quartz-rich Colorado River Delta sediments and sedimentary lithics. The dune height does not exert a control over the grain size distributions of the desert dune sands. The quartz enrichment of the desert dune sands may be due to wind sorting, which concentrates more quartz grains, and to the aeolian activity, which has depleted the feldspar grains through subaerial collisions. The desert dune sands suffer from little chemical weathering and they are chemically homogeneous, with chemical alteration indices similar to those found in other deserts of the world. The desert sands have been more influenced by sedimentary and granitic sources. This is supported by the fact that Ba and Sr concentration values of the desert sands are within the range of the Ba and Sr concentration values of the Colorado River quartz-rich sediments. The Sr values are also linked to the presence of Ca-bearing minerals. The Zr values are linked to the sedimentary sources and heavy mineral content in the desert dunes.
Proxy records of runoff, lake water salinity and aeolian activity, reconstructed by analyzing the concentrations of Ti, Ca and Zr/Ti in the sediments of palaeolake Las Cruces, provide information about millennial-scale summer season palaeohydrological changes at the southern margin of Chihuahua Desert over the last 8.4 cal. kyr BP. The data indicate generally higher-than-average runoff between c. 8.4 and 5 cal. kyr BP, correlative to the early Holocene Thermal Maximum. Except for the c. 2.2–2 cal. kyr BP humid event, runoff was lower than average over the last c. 5 cal. kyr BP. Latitudinal shifts in average position of the Inter-Tropical Convergence Zone (ITCZ) caused by long-term changes in summer insolation was the principal forcing behind the varying summer season precipitation and El Niño Southern Oscillation (ENSO) activity may explain some of the hydrological variability (e.g. higher-than-average summer precipitation during c. 2.2–2 cal. kyr BP). In general, the basin received more runoff during the periods of less frequent and weak ENSO, similar to the modern response to ENSO activity of the region. Significant increases in lake water salinity and aeolian activity over the last 2 cal. kyr BP correspond to stronger and more frequent ENSO during the late Holocene.
Marine Georesources & Geotechnology, 2008
A sedimentological, petrological and geochemical research work was carried out in order to fi nd out the origin and provenance of coastal and inland desert dunes from El Vizcaíno Desert, northwestern Mexico. Fifty four sand samples were collected from the windward, crest and slip face of coastal and desert dunes (barchan, transverse, aeolian sand sheets). Onshore winds generates fi ne, well sorted, near symmetrical dune sands with mesokurtic distributions in the El Vizcaíno Desert inherited from beach sands from the Vizcaíno bay. The coastal and inland dune sands are derived from nearby sand sources like the beach sands and also from alluvial deposits originated from sedimentary-volcanic and schists, granitic and granodiorite sources. This is evidenced by the presence of high quartz content, shell debris, carbonates, mica and hornblende that are constituents of the both coastal and inland dune sands and are probably derived from the action of longshore drifts and onshore winds. The El Vizcaíno coastal and inland dune sands are placed in the craton interior and recycled orogen fi elds in the Q-F-L diagram suggesting intrusive, sedimentary and partly metamorphosed sources in the composition of the sand. The geochemistry of the sands supports also the maturity process of the sands mainly associated with the presence of alluvial deposits and marine-aeolian action. Additionally, the El Vizcaíno dune sands are chemically related to acid rocks, felsic-plutonic detritus source rocks, which are associated to an active continental margin. The low chemical index of alteration (CIA) values in the dune sands suggest that dryness of the area plays a role in the preservation of labile minerals. The presence of volcanic, metamorphic and plutonic rock around the El Vizcaíno desert basin might contribute to the higher content of plagioclase and mica in the sands when compared to other North American deserts.
Geofísica Internacional
Con el propósito de documentar los cambios paleoambientales, se lleva a cabo una investigación multidisciplinaria en la Laguna Seca de San Felipe, Baja California. Los resultados preliminares incluyen análisis sedimentológicos de diatomeas y propiedades magnéticas de un núcleo de 9.5 m de longitud. Fechamientos de 14C sugieren que la secuencia abarca los últimos 70 000 años. Los resultados de propiedades magnéticas (χ, χfd%, MRIS, MRA, parámetros de histéresis y cocientes S), contenido de materia orgánica y tamaño de partículas indican condiciones contrastantes entre el último glacial del Pleistoceno y el glacial tardío-Holoceno. Se infieren condiciones secas entre 70 000 y 45 000 años A.P. El pleniglacial, entre 34 000 y 19 000 años A.P., está caracterizado por condiciones húmedas. A partir de 12 000 años A.P. la tasa de sedimentación y los parámetros magnéticos se incrementan en un factor de 5, cambio interpretado como el aumento en el escurrimiento de aguas superficiales. Entre...
We present elemental concentrations and magnetic susceptibility data from a new 270-cm-long sediment core collected from the western part of palaeolake Babicora and infer millennial-scale hydrological variations over the last 27 cal. ka in the western Chihuahua Desert. Variations in the available water content at the sediment-air interface of the watershed, lake salinity and lake productivity are inferred from values of the chemical index of alteration (CIA), CaCO3 and Corg, respectively. An abrupt increase in runoff at c. 24 cal. ka BP appears correlative with the Heinrich 2 (H2) event. Except for this event, diminished runoff between c. 27 and 19 cal. ka BP indicates lower annual precipitation (weak summer rainfall) during the Last Glacial Maximum. The deposition of chemically altered sediments between c. 25 and 22 cal. ka BP results from the higher sediment-water interaction in the watershed owing to lower evaporation, cooler conditions and higher precipitation during the H2 event. Since 19 cal. ka BP the runoff has been characterized by high-amplitude fluctuations with intervals of reduced precipitation identified at
Quaternary Science Reviews, 2013
We present a late Quaternary multi-proxy record from the paleolake Babicora in order to understand the influence of North American Monsoon (NAM) and westerly winter storms on the paleohydrological budget of the drylands of northern Mexico. Stratigraphy, 14 C chronology, mineral magnetism and geochemistry of the 976 cm long sediment core were used to reconstruct the hydrological conditions over the last 80 cal ka BP. The inverse relationship between the proxy records of runoff into Babicora and winter precipitation in southwestern USA indicate the minimal influence of westerly winter storms at 29 N during the Last Glacial period. Westerly winds transported minimally chemically altered sediments from the dry watershed during the cold stadials and the basin received more than average runoff as a result of a stronger NAM during the warm interstadials. The highest pluvial discharge occurred prior to 58 cal ka BP and terrestrial plants became the major contributor to organic matter deposited between 71 and 53 cal ka BP. Over the last 40 cal ka BP, the high amplitude fluctuations in runoff and lake water salinity mirrored an unstable summer rainfall regime.
Soil-geomorphology and “wet” cycles in the Holocene record of North-Central Mexico
Geomorphology, 2008
The distinction between the impact of climatic periodicities or land-use practices on soil erosion is an important issue for Pre-Hispanic and Colonial Mexico. That question can best be addressed by first documenting the dynamics of changing “wet” cycles during the Holocene in the central Mexican region between the northern limits of Pre-Hispanic agriculture and its southern margins in northwestern Chihuahua. Consequently the Laguna Project targeted a 125,000 km2 sector of North-Central Mexico, 250 km from north to south and 500 km from east to west, from Saltillo to Durango. Some 40 sedimentary profiles with multiple cumulic soils were studied in the field and laboratory, supported by 163 conventional 14C and AMS dates on charcoal and soil humates. We distinguish: (1) wet floodplains (with humic paleosols, redox phenomena reflecting high water tables, channel-ponding sequences, and interbedded tufas) that imply aquifer recharge, sustained base flow, and mainly low-energy conditions; and (2) high-energy pulses of discharge that mobilized cobble gravels or forced channel entrenchment (“gullying”) and were tied to episodic, excessive rains that promoted valley and slope instability. In between such “wet” cycles and recurrent disequilibrium events, climate was similar to today, probably less humid, with limited geomorphologic change or slow soil formation.“Wet” cycles were rare at the end of the Pleistocene, but prominent during the Holocene. Disequilibrium proxies became common and dramatic after 2500 BP. The drainages from the Eastern and Western Sierra Madres responded in phase, but varied in detail. Around AD 1050–1200 “natural” erosion led to loss of soil organic carbon, as alternating severe droughts and heavy rains destroyed the ground cover and led to ecological aridification, well before arrival of Spanish miners and settlers. The evidence that human activity triggered Pre-Hispanic or Colonial erosion in Central Mexico should therefore be re-evaluated. Global comparisons and interpretations are discussed, but with caution, since no single theory can explain the whole of the record. The soil-geomorphology geoarchive of North-Central Mexico primarily is an environmental history of alternating “wet” cycles, rather than of sustained wet or dry climates. The critical differences between “soaking” and “excessive” rains, with their respective impacts, may be due to switching between winter and summer storm categories.
Sedimentary differentiation of aeolian grains at the White Sands National Monument, New Mexico, USA
Aeolian Resesarch, 2017
Gypsum (CaSO 4 Á2H 2 O) has been identified as a major component of part of Olympia Undae in the northern polar region of Mars, along with the mafic minerals more typical of Martian dune fields. The source and age of the gypsum is disputed, with the proposed explanations having vastly different implications for Mars' geological history. Furthermore, the transport of low density gypsum grains relative to and concurrently with denser grains has yet to be investigated in an aeolian setting. To address this knowledge gap, we performed a field study at White Sands National Monument (WSNM) in New Mexico, USA. Although gypsum dominates the bulk of the dune field, a dolomite-rich [CaMg(CO 3) 2 ] transport pathway along the northern border of WSNM provides a suitable analog site to study the transport of gypsum grains relative to the somewhat harder and denser carbonate grains. We collected samples along the stoss slope of a dune and on two coarse-grained ripples at the upwind margin of the dune field where minerals other than gypsum were most common. For comparison, additional samples were taken along the stoss slope of a dune outside the dolomite transport pathway, in the center of the dune field. Visible and near-infrared (VNIR), X-ray powder diffraction (XRD), and Raman analyses of different sample size fractions reveal that dolomite is only prevalent in grains larger than 1mm.Otherminerals,mostnotablycalcite,arealsopresentinsmallerquantitiesamongthecoarsegrains.Theabundanceofthesecoarsegrains,relativetogypsumgrainsofthesamesize,dropsoffsharplyattheupwindmarginofthedunefield.Incontrast,gypsumdominatedthefinerfraction(<1 mm. Other minerals, most notably calcite, are also present in smaller quantities among the coarse grains. The abundance of these coarse grains, relative to gypsum grains of the same size, drops off sharply at the upwind margin of the dune field. In contrast , gypsum dominated the finer fraction (<1mm.Otherminerals,mostnotablycalcite,arealsopresentinsmallerquantitiesamongthecoarsegrains.Theabundanceofthesecoarsegrains,relativetogypsumgrainsofthesamesize,dropsoffsharplyattheupwindmarginofthedunefield.Incontrast,gypsumdominatedthefinerfraction(<1 mm) at all sample sites, displaying no spatial variation. Estimates of sediment fluxes indicate that, although mineralogical differentiation of wind-transported grains occurs gradually in creep, the process is much more rapid when winds are strong enough to saltate the P1 mm grains. The observed grain segregation is consistent with the WSNM dune field formative friction velocity (0.39 m/s) proposed by Jerolmack et al. (2011): winds significantly weaker than this value would not lift the large grains into differentiation-inducing saltation, whereas the observed differentiated trend would be obliterated by significantly stronger winds. When applied to Olympia Undae, a similar sediment flux analysis suggests that the strongest winds modeled by the Mars Climate Database (MCD) are consistent with the observed concentration of gypsum at dune crests. Density-driven differentiation in transport should not influence sediment fluxes of finer grains (<1 mm) as strongly on Earth, suggesting that the high ratio of fine gypsum grains to other minerals at WSNM is caused by a relatively high production and/or abrasion rate of gypsum sand. The observed preferential transport of coarse-grained gypsum in the dune field conceals a broader range of coarse-grained minerals present on Alkali Flat, contributing to the problem that mineralogy determined through both remote sensing of dune fields and analysis of dune foresets does not fully represent that of the source regions. Unlike quartz, the concentration of gypsum in WSNM occurs not because it is more resistant to weathering and erosion than other minerals, but rather because it is more readily produced (in the case of finer grains) and transported (in the case of coarser grains) than other minerals present in the region.