Thanks to the funding provided by the CICYT commision in Spain we are currently working on lake sediments from the Chilean Altiplano. The group is constituted by the collaboration of our institute with people from the University of Barcelona (Dr. A. Sáez, Dr. J.J. Pueyo), the Earth Science Institute "Jaume Almera" (Dr. C. Taberner and Dr. S. Giralt) and the University of A Coruña (Dr. R. Bao). Most of our work has been done in the framework of the ANDESTER project, recently finished:

Project: ANDESTER (Origen de los solutos y evolución paleohidrológica en sistemas lacustres cuaternarios con influencia hidrotermal; Altiplano de los Andes Centrales).

Period: 28 Dec 2001 - 27 Dec 2004

Funding: CICYT, Ministerio de Ciencia y Tecnología, Spain

Principal Investigators: A. Sáez, B. L. Valero-Garcés, C. Taberner, J. J. Pueyo, R. Bao, S. Giralt, A. Moreno, P. González-Sampériz, C. Herrera.

Lago Chungará in November 2002 during the field expedition

During ANDESTER project, up to 15 sediment cores were recovered from Lago Chungará (Northernl Chile Altiplano) with the coring platform from the Limnological Research Center (University of Minnesota). In addition, two water sampling campaigns were carried out to perform geochemical analyses in the water samples. The sediment cores were opened and described following the protocols defined in the Limnological Research Center and sampled for many different studies, some them in progress: diatoms, pollen, ostracods, carbon content, mineralogy, stable isotopes, etc. Here you can see some pictures of the sampling procedures.

Sampling Chungará cores in the IPE laboratory

In addition, cores 10A and 11A were analysed by the XRF Core Scanner from the University of Bremen thanks to the Paleostudies programme, obtaining continous geochemical measurements that are very useful to discriminate the presence of volcanic an carbonate layers (see an example). Age model was constructed after several 14C and U/Th dates resulting in a continuous sequence since 13000 cal yr BP. Preliminary results are going to be presented in several international conferences (see conferences page):

1.- Abstract for the 2004 AGU Fall meeting, 13-17 December, San Francisco, USA

Blas Valero-Garcés, Ana Moreno, Penelope Gonzalez-Samperiz, Alberto Saez, Roger Oriol Gibert, Juan Jose Pueyo, Conxita Taberner, Santiago Giralt, Roberto Bao, Larry Edwards, Doug Schnurrenberger, Amy Myrbo, Mark Shapley, Cristian Herrera and Antje Schwalb. A Holocene record of hydrological fluctuations from Lago Chungara (Chilean Altiplano)

The Holocene records of moisture availability in the Central Andes and the Altiplano show contrasting and even opposite signals and time-transgressive millennial-scale climatic changes across the region. The available records also evidence a pronounced north-south regional heterogeneity, particularly between the Titicaca Basin and the Atacama Altiplano. A multiproxy study of a 13 kyr record of Lago Chungará (18° 15' S, 69° 10' W, 4520 m a.s.l. Chilean Altiplano) provides new data to solve some of the paleoclimate controversies as regional moisture availability patterns during the early and mid Holocene and the onset of ENSO modern conditions.
Lago Chungará originated after the emplacement of the Parinacota volcano debris avalanche that blocked the Chungará River prior to 13 cal. kyrs ago. A seismic survey and fifteen Kullenberg cores allowed a detailed 3-D reconstruction of the sedimentary sequence (8 m). The chronological model is based on 5 AMS 14C on bulk organic matter and 3 U/Th dates on authigenic carbonates and shells. To assess the typically large (and variable) reservoir effect, we dated modern sediments and waters, and constrained the model with time markers based on a 210Pb age model for the last 150 yrs, volcanic ashes of known age, and the U/Th dates. We performed high–resolution analyses by an X-ray fluorescence core scanner and magnetic, sedimentological, mineralogical, isotopic, and biological (pollen, diatoms and ostracods) analyses on selected cores. Statistical analyses helped to separate the volcanic from the climate signal as the key driving forces in the hydrological and sedimentological evolution of the lake. Three main units are identified over the pre- collapse substrate. The basal unit (13 - 7.2 cal. kyrs BP) is a finely laminated diatomite. Preliminary analyses suggest a dominant interannual frequency that could be related to ENSO activity. The middle unit (7.2 – 4.5 cal. kyrs BP) is banded and it comprises diatomites and some carbonate-rich layers. Increased volcanic activity after 6 cal kyrs BP and climate-driven hydrological changes seem to have been conducive to increase carbonate precipitation during this period. The upper unit (after 4.5 cal. kyrs BP) is banded to massive and it contains abundant volcanic layers (lapilli, ash layers). Seismic features identified in littoral areas and interpreted as evidence for lower lake level periods and a subsequent raise seem to correlate with the middle unit and the transition to the upper unit.
The reconstructed hydrological variability in the Lake Chungara shows fluctuating lake levels during the early Holocene (13 to 7.2 cal kyrs BP), and the mid Holocene (7.2 – 4.5 cal kyrs BP), and the highest lake levels during the late Holocene. The laminated basal unit suggests that ENSO-like variability was also present during the early Holocene in the Altiplano. The presence of mid – Holocene arid intervals supports the regional extent of this period of reduced moisture through the region.

2.- Abstract for the EGU General Assembly, 24-29 April, 2005, Vienna, Austria:

Moreno, A. (1); Giralt, S. (2); Valero-Garcés, B. L. (1); Sáez, A. (3); Bao, R. (4); Pueyo, J.J. (3); González-Sampériz, P. (1); Oriol, R. (3), Taberner, C. (2). Effects of climate, lake productivity and volcanic influences unraveled for last 13000 years in the Central Chilean Altiplano: a high-resolution geochemical study

(1) Pyrenean Institute of Ecology - CSIC, Apdo 202, 50080 Zaragoza, Spain, (2) Institute of Earth Sciences Jaume Almera - CSIC, Lluis Sole i Sabaris s/n, 08028 Barcelona, Spain, (3) Faculty of Geology, University of Barcelona, Marti i Franques s/n, 08028 Barcelona, Spain, (4) Universidade da Coruña, Facultade de Ciencias, Campus da Zapateira s/n, 15071 A Coruña, Spain

Available records from the Central Andes and the Altiplano evidence a pronounced heterogeneity in the regional moisture availability during the Holocene. The multiproxy study (seismic survey, high-resolution geochemical profiles carried out by a XRF Core Scanner, mineralogical composition, TIC, TOC, biogenic silica and diatoms) of the Lago Chungará sedimentary infill (18° 15' S, 69° 10' W, 4520 m a.s.l. Chilean Altiplano) has provided new insights which could contribute to solve some of the regional paleoclimate controversies, such as the Mid-Holocene aridity crisis or the onset of ENSO conditions.
A seismic survey and fifteen Kullenberg cores (up to 8 m long) allowed a detailed 3-D reconstruction of the sedimentary architecture. The chronological framework of the cores was established using 13 radiocarbon and 4 238U/230Th dates, allowing to reconstruct the lacustrine evolution for the last 13,000 cal years BP. Three main sediment sources were distinguished along the record: volcanic supply from the nearby volcanoes (represented by Fe, Ti, K and % of plagioclase), endogenic carbonate production (highlighted by the Ca/Ti, Sr/Ti, % calcite and TIC variations) and bioclastic remains, mainly diatoms (Si/Ti, biogenic opal, S/Ti, %TOC).
Three main units were identified over the pre-collapse substrate:
1.- The basal unit (13 - 7.2 cal. kyrs BP) is a finely laminated diatomite. Preliminary analyses suggest a dominant interannual frequency that could be related to the ENSO activity. Furthermore, our records indicate an increase in productivity during the Early Holocene, coherent with the raise of paleotemperatures in the nearby Sajama ice core.
2.- The middle unit (7.2 – 4.5 cal. kyrs BP) is banded and it comprises diatomites and some carbonate-rich layers. Increased volcanic activity after 6 cal kyrs BP and climate-driven hydrological changes seemed to be the main promoters of the carbonate precipitation that occurred during this period. An arid Mid-Holocene is recorded in the Lago Chungará sediments supporting the regional low moisture availability of this period.
3.- The upper unit (after 4.5 cal. kyrs BP) is banded to massive and it contains abundant volcanic layers (lapilli, ash layers). A high correlation between the volcanic input in Lago Chungará and the total particles coarser than 63 µm recorded in the Sajama ice core is evident for the last 6000 years.
The high-resolution attained in this study allowed us to identify several sharp and abrupt episodes of climate change during the Holocene, such as those observed during the Mid-Holocene (among 7.5 and 5.5 kyrs) and the 8.2 kyrs event. Timing of these events and their potential climatic forcings are discussed in comparison with adjacent records, such as those from Lake Titicaca.

3.- Abstract for the Conference on the El Niño phenomenon and its global impact, 16-20 May, 2005 Guayaquil, Ecuador:
S. Giralt (1), A. Moreno (2), B. Valero (2), A. Saez (3), R. Bao (4), C. Taberner (1), J.J. Pueyo (5), P. Gonzalez (2), C. Herrera (6), The sedimentary record of Lago Chungara (Chilean Altiplano): a high resolution archive of the ENSO phenomenon during the late Glacial and Early Holocene

(1) Institute of Earth Sciences 'Jaume Almera' (CSIC), Lluis Sole i Sabaris s/n, E-08028 Barcelona (Spain), sgiralt@ija.csic.es
(2) Institute of Pyrenean Ecology (CSIC), Apdo 202, E-50080 Zaragoza (Spain)
(3) Dept. of Stratigraphy, Paleontology and Marine Geosciences, Faculty of Geology, University of Barcelona, Marti i Franques s/n, E-08028 Barcelona (Spain)
(4) Faculty of Sciences, University of A Coruña, Campus da Zapateira s/n, E-15071 A Coruña (Spain)
(5) Dept. of Geochemistry, Faculty of Geology, University of Barcelona, Marti i Franques s/n, E-08028 Barcelona (Spain)
(6) Dept. of Geological Sciences, University 'Catolica del Norte', Avda. Angamos, 060010 - Casilla 1280, Antofagasta (Chile)

The Central Andes and the Altiplano has provided exceptional records of climate variability of the last millenia, but little is known about the mechanisms and processes that have triggered such variability. A high-resolution multiproxy study of the sedimentary record of Lago Chungara (18°15'S, 69°10'W, 4520 m a.s.l., Chile an Altiplano) provides new data to solve some of the paleoclimate controversies as regional moisture availability patterns during the Late Glacial and Early Holocene and the onset of ENSO modern conditions.
A seismic survey and fifteen Kullenberg cores (8 m long) allowed a detailed 3-D reconstruction of the sedimentary sequence as well as to define the major hydrological and climatic episodes. The recovered sedimentary sequences show three main units. The basal unit is minly composed by rhythms and cycles of different lamina constituted by diatomaceous ooze with carbonates and organic matter. The middle unit is banded and it comprises diatomites, volcanoclastic and carbonate-rich layers. The upper unit is banded to massive and it contains abundant volcanoclastic layers (ashes/ignimbrites).
X-ray fluorescence core scanner every 2 mm and magnetic, sedimentological, mineralogical, isotopic, gray curve (one sample every 0.1 mm) and biological (pollen, diatoms and ostracods) analyses were performed on two selected cores (Core 10 and 11) in order to characterize the environmental evolution of the lake. The chronological model of these sedimentary sequences is based on 5 AMS 14C and 3 238U/230Th.
Statistical analyses (cluster and detrended correspondence (DCA) analyses) were employed to separate the volcanic from the climate signal, as the key driving forces in the hydrological and sedimentological evolution of the lake. The volcanic signal appeared in the first eigenvector of the analyses whereas the climatic signal was reconstructed from the segon eigenvector of the DCA. The climatic signal seems to be related with the productivity oscillations of the lake. Spectral analyses (Fast Fourier Transformation (FFT) and Time Frequency (TF) analyses) were performed in order to characterize the temporal evolution of the climate signal.
Here we will present the results of the basal laminated unit. According to the chronological framework this unit comprises the Late Glacial - Holocene transition (approx. 12,800 - 9,800 calendar radiocarbon years).
The FFT analyses of the climate signal obtained from the DCA for the basal laminated unit highlight the presence of cyclicity of 35 - 51 years, which could be interpreted as the solar Bruckner cycle as well as interdecadal changes in the variance of the ENSO phenomenon. The FFT analyses results carried out on the gray curve also reinforce the hypothesis of the solar control of the productivity of the lake (due to the presence of the 11-years Schwalbe, the 22 - 23-years Hale, the 35-years Bruckner and the approx. 90-years Gleissberg cycles), as well as the presence of strong to very strong ENSO phenomenon (8.2 and 7.5-years cycles). The TF analyses developed on the gray curve suggest that the solar activity and the ENSO phenomenon were not always active during the same period of time.

"Future" work in the Chilean Altiplano

Recently, we have started with a new project funded by the CICYT (Ministerio de Educación y Ciencia, Spain) called LAVOLTER:

Project: LAVOLTER (Fenómenos extremos en el registro sedimentario de lagos en contexto volcánico-hidrotermal activo).

Period: 13 Dec 2004 - 13 Dec 2007

Funding: CICYT, Ministerio de Ciencia y Tecnología, Spain

Principal Investigators: C. Taberner, A. Sáez, B. L. Valero-Garcés, J. J. Pueyo, R. Bao, S. Giralt, A. Moreno, P. González-Sampériz, C. Herrera.

In the framework of this project we will address the study of several Quaternary lake records in the Pacific area, 1) with different degrees of geothermal control and 2) under the influence of the El Niño Southern Oscillation. The objective is the discrimination and evaluation of climatic signatures versus those related to volcanic and geothermal activity in the area. Two lakes with different geothermal activity have been selected in the Altiplano of Northern Chile (Chungará and Surire). The three lakes of the Eastern Island have been chosen for the lack of thermal springs and for their location with respect to the El Niño Southern Oscillation. This proposal has developed as a natural follow up of the previos ANDESTER project. Main objectives of LAVOLTER project are: 1) differentiation of climatic signatures in a hydrothermal-volcanic context, from those strictly climatic, in lacustrine sediments; and 2) calibration and evaluation of the signatures recorded in the selected lake records, based upon the variability of the sedimentary record in the same lake system and the recorded variability between the selected lake systems. The isolation of the strictly climatic signatures from those related to other processes in lake records is of extreme interest in the interpretation of the past climatic variability and its use as a predictive tool of climatic variability derived of the Global Climate Change. Results of this project will enable the differentiation and isolation of climatic signatures from signatures related to local perturbations, mainly related to geothermal processes.

Previous work in the Chilean Altiplano

Our work in South America started almost ten years ago from our collaboration with the University of Bern (Switzerland), and the Limnological Research Center (University of Minnesota, USA) in the study of lakes in the Chilean Altiplano. The collaboration with the Departments of Archaeology of the University of Buenos Aires and the Universidad Nacional de Catamarca has helped to span our activities to the Argentinian Altiplano. Several lacustrine records from high altitude Chilean and Argentinian lakes have shown a strong signature of the Little Ice Age in the Altiplano. Besides, many records indicate a large effective moisture variability at decadal scale.