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  • Holocene  (3)
  • Caves diameter  (2)
  • C32
  • 1
    ISSN: 1573-0417
    Keywords: saline lakes ; stable isotope ; sedimentology ; mineralogy ; paleohydrology ; Altiplano ; Holocene ; Little Ice Age
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The paleohydrological evolution of several high altitude, saline lakes located in the southernmost Altiplano (El Peinado and San Francisco basins, Catamarca province, NW Argentina) was reconstructed applying sedimentological, geochemical and isotopic techniques. Several playa lakes from the San Francisco basin (26° 56′ S; 68° 08′ W, 3800-3900 m a.s.l.) show evidence of a recent raise in the watertable that led to modern deposition of carbonate and diatomaceous muds. A 2 m - long core from El Peinado Lake (26° 29′ 59′′ S, 68°05′ 32′′ W, 3820 m a.s.l.) consists of calcitic crusts (unit 3), overlaid by an alternation of macrophyte-rich and travertine clast- rich, laminated muds (unit 2), and topped by travertine facies (unit 1). This sedimentary sequence illustrates a paleohydrological evolution from a subaerial exposure (unit 3) to a high lake stand (unit 2), and a subsequent smaller decrease in lake level (unit 1). The δ13Corganic matterrecord also reflects the lake transgression between units 3 and 2. Although there is a general positive correlation between δ 18Ocarbonate and salinity proxies (Na, Li and B content), the large data dispersion indicates that other factors besides evaporation effects control chemical and isotopic composition of lakewater. Consequently, the oxygen isotopic composition cannot be interpreted exclusively as an indicator of salinity or evaporation ratio. The degassing of CO2 during groundwater discharge can explain the enriched δ13C values for primary carbonates precipitated. The carbon budget in these high altitude, saline lakes seems to be controlled by physical rather than biological processes.The Altiplano saline lakes contain records of environmental and climatic change, although accurate 14C dating of these lacustrine sediments is hindered by the scarcity of terrestrial organic material, and the large reservoir effects. Sedimentologic evidence, a 210Pb-based chronology, and a preliminary U/Th chronology indicate a very large reservoir effect in El Peinado, likely as a result of old groundwaters and large contributions of volcanic and geothermal 14C-free CO2 to the lake system. Alternative chronologies are needed to place these paleorecords in a reliable chronological framework. A period of increased water balance in the San Francisco basin ended at about 1660 ± 82 yr B.P. (calendar yr U/Th age), and would correlates with the humid phase between 3000 and 1800 yr B.P detected in other sites of the southern Altiplano. Both, 210Pb and preliminary U/Th dating favor a younger age for the paleohydrological changes in El Peinado. The arid period reflected by subaerial exposure and low lake levels in unit 3 would have ended with a large increase in effective moisture during the late 17th century. The increased lake level during deposition of unit 2 would represent the period between AD1650 - 1900, synchronous to the Little Ice Age. This chronological framework is coherent with other regional records that show an abrupt transition from more arid to more humid conditions in the early 17th century, and a change to modern conditions in the late 19th century. Although there are local differences, the Little Ice Age stands as a significant climatic event in the Andean Altiplano.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-0417
    Keywords: sedimentology ; saline lake ; meromixis ; Northern Great Plains ; Holocene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Medicine lake is a small (about 1 km2), shallow (up to 10 m deep), saline (50–170 g l−1) and meromictic lake formed after the retreat of the Wisconsin ice in the north American Great Plains. Based on a detailed sedimentological analysis of cores, we describe and interpret 13 sedimentary subfacies grouped in 9 associations which characterize the following lacustrine subenvironments: clastic littoral (freshwater and saline), springs, microbial mats, bench slope, and pelagial (oxic, alternating oxic-anoxic, anoxic and hypersaline, and organic-dominated). Lateral distribution and vertical evolution of subfacies in our model are controlled by climate fluctuations, climate-related limnological parameters (lake level, TDS and brine composition, and redox conditions), and autocyclic processes (progressive infilling of the basin and higher sedimentation rate in the pclagial realm). Microbial and chemical processes govern deposition in this system, and meromixis plays a decisive role in lake dynamics. Phototropic bacterial plate communites at the chemocline dominated as pelagial organic producers during stable meromictic periods, whereas benthic microbial communities developed during mixed water periods. Water stratification during the Holocene was mainly controlled by three parameters: 1) basin morphometry, 2) lake level, and 3) differences in TDS values between mixolimnion and monimolimnion waters. Sedimentary facies analyses is a powerful descriptive and interpretative tool that greatly contributes to deciphering the high resolution paleoenvironmental information archived in lake sequences. Depositional and paleoenvironmental models provide a dynamic framework for integrating paleolimnological data and other proxy paleorecords. Medicine lake serves as a facies model for shallow, perennial hypersaline, meromictic lakes in modern and ancient lacustrine basins. The sediment sequence from Medicine lake cores is consistent with the general paleoclimatic evolution of the northern Great Plains since the retreat of ice sheets. Our study reveals a plethora of rapid fluctuations in the water cycle both during the middle and the late Holocene. These augment prior paleoclimate reconstructions based on diatom studies of the lower Holocene freshwater to saline transition and on pollen profiles which show little variability during the subsequent long prairie grass episode.
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  • 3
    ISSN: 1573-0417
    Keywords: Atacama ; Holocene ; limnogeology ; South America ; paleoclimatology ; lake sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Sedimentological, mineralogical and geochemical analyses of sediment cores from 9 m-deep, saline Laguna Miscanti, Chile (23 ° 44′S, 67 °46′W, 4140 m a.s.l.) together with high-resolution seismic profiles provide a mid to late Holocene time series of regional environmental change in the Atacama Altiplano constrained by 210Pb and conventional 14C dating. The mid Holocene was the most arid interval since the last glacial maximum, as documented by subaerial exposure and formation of hardgrounds on a playa surface. Extremely low lake levels during the mid Holocene appear consistent with lower effective moisture recorded at other sites along the Altiplano and in the Amazon Basin. Termination of this arid period represented a major shift in the regional environmental dynamics and inaugurated modern atmospheric conditions. The cores show a progressive upward increase in effective moisture interrupted by numerous century-scale drier periods of various intensities and durations that characterize a fluctuating late Holocene climate. In spite of chronological uncertainties, the major environmental changes seem to correlate with the available paleorecords from the region providing a coherent account of effective moisture variability in the tropical highlands of South America.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2021-05-19
    Description: El cangrejo de tierra Cardisoma guanhumi, (Latreille, 1825) habita en el Parque Nacional Ciénaga de Zapata y constituye un recurso de importancia comercial. Se determinó la densidad media de la población de C. guanhumi en las zonas de captura Guamutal, El Maíz, La Arenera y Bolanio. Se utilizó un método de estimación indirecta y se muestrearon 11 parcelas de 81 m2 en febrero/2013 para un área total de 748 m2; además, se realizaron muestreos mensuales durante la temporada de captura (mayo, junio y julio del 2013). La densidad media de cuevas varió de 0,52 a 2,23 cuevas/m2, con una media de 1,43 cuevas/m2. La zona de mayor densidad fue La Arenera con 1,81 cuevas/m2 y la menor Bolanio con 0,52 cuevas/m2. El diámetro promedio de las cuevas fue de 10,13 ± 0,34 cm, 7,74 ± 0,56 cm y 5,59 ± 0,30 cm en El Maíz, La Arenera y Guamutal respectivamente. Se observaron diferencias significativas entre los diámetros medios. Los valores de menor diámetro en Guamutal refuerzan la hipótesis de que ésta constituye una zona de reclutamiento. La talla media del cangrejo disminuye a medida que trascurre la corrida. La captura posee un esquema de “Libre Acceso” y por ello se considera al cangrejo explotado intensamente, con disminución de la talla media de captura e incremento de ejemplares por debajo de la talla mínima legal. La presencia de cangrejos está asociada a los mangles Laguncularia racemosa y Conocarpus erectus. La fauna asociada a C. guanhumi la constituyen cangrejos ermitaños (Eupagurus sp.), cocodrilos (Crocodylus rhombifer) y perros jíbaros (Canis familiares).
    Description: At the National Park, Cienaga de Zapata inhabits the land crab (Cardisoma guanhumi, Lattreille, 1825) constituting a resource of commercial importance. To determinate the average density of the population in the catchment areas Guamutal, El Maiz and La Arenera, it was used an indirect method; it were sampled 11 locations with 81 m2 at febrary/2013 for a total area of 748 m2. Also there were done monthly samples to the capture during the capture season. The caves average density varied from 0,52 to 2,23 caves/m2, with an overall average of 1,43 caves/m2. The area most densely populated was La Arenera with 1,81 caves/m2 and the lower was Bolanio with 0,52 caves/m2. The average diameter of the caves was 10,3±0,34cm, 7,74±0,56cm and 5,59±0,30cm in El Maiz, La Arenera and Guamutal respectively. There is significant difference between the mean diameters. The presence of small diameters caves in Guamutal reinforces the hypothesis that this is the main area of recruitment. The crab average size decrease along the capture season. His capture has a “Free Access” scheme and crab is considered as intensely exploited. The percentage of specimens below the legal minimum size has been increased and therefor the average size has decreased. The crab presence is associated with gender mangrove, Laguncularia racemosa and Conocarpus erectus. In the fauna associated with C. guanhumi there were observed the hermit crabs (Eupagurus sp.), crocodiles (Crocodylus rhombifer) and wild dogs (Canis familiares).
    Description: Published
    Keywords: Cardisoma guanhumi ; Densidad de población ; Diámetro de cuevas ; Flora y fauna asociada ; Cuba ; Population density ; Caves diameter ; Flora y fauna associated
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed
    Format: pp.110-124
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  • 5
    Publication Date: 2021-05-19
    Description: El cangrejo de tierra Cardisoma guanhumi, (Latreille, 1825) habita en el Parque Nacional Ciénaga de Zapata y constituye un recurso de importancia comercial. Se determinó la densidad media de la población de C. guanhumi en las zonas de captura Guamutal, El Maíz, La Arenera y Bolanio. Se utilizó un método de estimación directa y se muestrearon 11 parcelas de 81 m2 en febrero/2013 para un área total de 748 m2; además, se realizaron muestreos mensuales durante la temporada de captura (mayo, junio y julio del 2013). La densidad media de cuevas varió de 0,52 a 2,23 cuevas/m2, con una media de 1,43 cuevas/m2. La zona de mayor densidad fue La Arenera con 1,81 cuevas/m2 y la menor Bolanio con 0,52 cuevas-m2. El diámetro promedio de las cuevas fue de 10,13 +- 0,34 cm, 7,74 +- 0,56 cm y 5,59 +- 0,30 cm en El Maíz, La Arenera y Guamutal respectivamente. Se observaron diferencias significativas entre los diámetros medios. Los valores de menor diámetro en Guamutal refuerzan la hipótesis de que esta constituye una zona de reclutamiento. La talla media del cangrejo disminuye a medida que transcurre la corrida. La captura posee un esquema de "Libre Acceso" y por ello se considera al cangrejo explotado intensamente, con disminución de la talla media de captura e incremento de ejemplares por debajo de la talla mínima legal. La presencia de cangrejos está sociada a los mangles Laguncularia racemosa y Conocarpus erectus. La fauna asociada a C. guanhumi la constituyen cangrejos ermitaños (Eupagurus sp.), cocodrilos (Crocodylus rhombifer) y perros jíbaros (Canis familiares).
    Description: At the National Park, Cienaga de Zapata inhabits the land crab (Cardisoma guanhumi, Latreille, 1825) constituting a resource of commercial importance. To determinate the average density of the population in the catchment areas Guamutal, El Maíz and La Arenera, it was used and indirect method; it were sampled 11 locations with 81 m². Also there were done monthly samples to the capture during the capture season. The caves average density varied from 0.52 to 2.23 caves/m², with an overall average of 1.43 caves/m². The area most densely populated was La Arenera with 1.81 caves/m² and the lower was Bolanio with 0.52 caves/m². The average diameter of the caves was 10,13 ± 0,34 cm, 7,74 ± 0,56 cm and 5,59 ± 0,30 cm in El Maíz, La Arenera and Guamutal respectively. There is significant differences between the mean diameters. The presence of small diameter caves in Guamutal reinforce the hypothesis that this is the main area of recruitment. The crab average size decreases along the capture season. His capture has a "Free Access" scheme and crab is considered as intensely exploited. The percentage of specimens below the legal minimum size has been increased and therefor the average size has decresead. The crabs presence is associated with gender mangroves, Laguncularia racemosa and Conocarpus erectus. In the fauna associated with C. guanhumi there were observed the hermit crabs (Eupagurus sp.), crocodiles (Crocodylus rhombifer) and wild dogs (Canis familiaris).
    Description: Published
    Keywords: Cardisoma guanhumi ; Densidad de población ; Diámetro de cuevas ; Flora y fauna asociada ; Population density ; Caves diameter ; Flora and fauna associated
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed
    Format: pp.110-124
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