Mid- and late-Holocene limnogeology of Laguna del Negro Francisco, northern Chile, and its palaeoclimatic implications

Grosjean, Martín; Valero‐Garcés, Blas L.; Geyh, Mebus A.; Messerli, Bruno; Schotterer, U.; Schreier, Hans; Kelts, Kerry

doi:10.1177/095968369700700203

Cited by 82 publications

(74 citation statements)

References 11 publications

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“…1; Valero-Garcés et al, 2003) showed wide variations in composition and hydrology in the last centuries. Research has also been undertaken on geochemical signatures in endogenic carbonates in other lakes in the area (Laguna Seca, Miscanti and Negro Francisco) in an attempt to reconstruct climatic changes since the Last Glacial Maximum (Grosjean, 1994;Grosjean et al, 1997;Schwalb et al, 1999;Valero-Garcés et al, 1999b;Grosjean et al, 2001;Valero-Garcés et al, 2003;Theissen et al, 2008).…”

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Carbonate and organic matter sedimentation and isotopic signatures in Lake Chungará, Chilean Altiplano, during the last 12.3kyr

Pueyo

Sáez

Giralt

et al. 2011

Palaeogeography, Palaeoclimatology, Palaeoecology

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Sediments in lakes in the Andean volcanic setting are often made up of diatomaceous ooze together with volcaniclastics and small amounts of carbonates. Despite their scarcity, carbonates along with organic matter provide significant paleoenvironmental information about lake systems. This study focuses on the carbonates in Lake Chungará, their morphologies, distribution and origin deduced from the isotopic markers. These markers reflected changes in the water and the biomass between the onset of the Holocene and around 9.6 cal kyr BP. These changes are marked by general increases in TOC, TN, and TN-δ 15 N AIR , and by fluctuating values of TOC-δ 13 C VPDB in its sediments and are probably related to major shifts in the lake surface/volume associated with rises in lake level. An increase in salinity around 10 cal kyr BP is thought to be linked to a short dry period, giving rise to the onset of carbonate production. The mid-Holocene arid period between 7.3 and 3.5 cal ka BP, with a maximum of aridity around 6.0 cal kyr BP, was deduced from δ 18 O VPDB values in the endogenic carbonates. These results match the reconstructions in Lake Titicaca based on benthic diatoms and paleoshore levels. Offshore sediments mainly consist of a diatomaceous ooze, laminated in the lower half (Unit 1), and bandedmassive with tephra layers in the upper half of the sequence (Unit 2). TOC-δ 13 C VPDB and the C/N ratio confirm that phytoplankton was the main source of organic matter in these sediments. Shallower sediments (units 3 to 5) developed in platform and littoral settings, providing evidence of subaqueous macrophytes and, to a lesser extent, land plants. Carbonate content ranges between 0.1 and 6 wt.% in offshore settings (30 to 40 m water depth) and reaches the maximum values in the lower part of Unit 2. Carbonate minerals (low magnesium calcite and minor amounts of high magnesium calcite and aragonite) are scarce and are arranged in mm-thick layers, commonly forming cm-thick levels or bioclasts. Carbonate layers are made up of euhedral-to-subhedral spindle-shaped calcite crystals and, to a lesser extent, aragonite needles, all in the μm range. Aragonite spheroids coexist in littoral sediments with other carbonate shapes and charophyte remains, where carbonate reaches locally up to 20 wt.%. CO 2 photosynthetic depletions related to seasonal phytoplankton blooms were responsible for the high frequency deposition of mm-thick carbonate layers.The average values for δ 13 C VPDB in lake water, plankton and sediments of Lake Chungará (as organic matter or as carbonate) are around 15‰ higher than commonly reported values in other lakes. This 13 C enrichment is attributed to carbon assimilation from a DIC affected by methanogenesis, in which HCO 3 − is the dominant species. The δ 13 C VPDB and δ 18O VPDB variations and their covariation in endogenic carbonates suggest that lake water volume and lake level increased along the Holocene.

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confidence: 99%

Carbonate and organic matter sedimentation and isotopic signatures in Lake Chungará, Chilean Altiplano, during the last 12.3kyr

Pueyo

Sáez

Giralt

et al. 2011

Palaeogeography, Palaeoclimatology, Palaeoecology

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“…Oprecipitation is a function of the isotope composition of the moisture source and air-mass trajectory, but in the Lago Chungará there are not changes in the moisture source composition since the air masses always come from the Atlantic Ocean throughout the Amazon basin (Grosjean et al 1997).…”

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ENSO and solar activity signals from oxygen isotopes in diatom silica during late glacial-Holocene transition in Central Andes (18°S)

et al. 2010

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The Late Glacial-Holocene transition from the Lago Chungará sedimentary record in northern Chilean Altiplano (18ºS) is made up of laminated sediments composed of light and dark pluriannual couplets of diatomaceous ooze. Light sediment laminae accumulated during shortterm extraordinary diatom blooms whereas dark sediment laminae represent the baseline limnological conditions during several years of deposition. Diatom oxygen isotope data Odiatom record documents repeated effective moisture changes at a centennial-scale. Three major cycles have been established (11,990 to 11,800, 11,800 to 11,550 and 11,550 to 11,450 cal years BP). Each cycle is defined by an increasing isotope trend followed by a sudden depletion of the isotope values. In addition, several wet and dry events at a decadal scale are superimposed onto these major cycles. The spectral analyses of the δ 18Odiatom values suggest that cycles and events could be triggered by both the El Niño-Southern Oscillation (ENSO) and the solar activity. Significant ENSO frequencies of 7-9 years and 15-17 years, and periodicities of the solar activity cycles such as 11 yr (Schwabe), 23 yr (Hale) and 35 yr (Brückner) have been recognized in the oxygen isotope time series. Time-frequency analysis shows that the activity of these two forces,, although was also present in the onset of the Holocene, it was more intense during the Late Glacial period. The early Holocene could be mainly governed by La Niña-like conditions that correspond to wet conditions over the Andean Altiplano.

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“…Por lo tanto, los resultados para la laguna Miscanti posiblemente dan cuenta de un patrón más regional significativo in toto (Grosjean et al� 1997).…”

Section: Aridez Y Flujos De Tormentas Durante El Holoceno Mediounclassified

Cambios ambientales holocénicos en la Puna de Atacama y sus implicancias paleoclimáticas

Núñez

Grosjean

Messerli³

et al. 1997

Estud Atacameños

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Mid- and late-Holocene limnogeology of Laguna del Negro Francisco, northern Chile, and its palaeoclimatic implications

Cited by 82 publications

References 11 publications

Carbonate and organic matter sedimentation and isotopic signatures in Lake Chungará, Chilean Altiplano, during the last 12.3kyr

Carbonate and organic matter sedimentation and isotopic signatures in Lake Chungará, Chilean Altiplano, during the last 12.3kyr

ENSO and solar activity signals from oxygen isotopes in diatom silica during late glacial-Holocene transition in Central Andes (18°S)

Cambios ambientales holocénicos en la Puna de Atacama y sus implicancias paleoclimáticas

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