Palaeogeography, Palaeoclimatology, Palaeoecology 427 (2015) 20–31 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo Late Glacial and Early Holocene cyclic changes in paleowind conditions and lake levels inferred from diatom assemblage shifts in Laguna Potrok Aike sediments (southern Patagonia, Argentina) Claudia Zimmermann a,⁎, Guillaume Jouve b,1, Reinhard Pienitz c,2, Pierre Francus b,1,NoraI.Maidanad a Centre d'études nordiques (CEN), Université Laval, Pavillon Abitibi-Price, Room 1230, 2405, rue de la Terrasse, Québec, QC, G1V 0A6, Canada b Centre Eau Terre Environnement, Institut National de la Recherche Scientifique (INRS-ETE), 490, rue de la Couronne, Québec, QC, G1K 9A9, Canada c Centre d'études nordiques (CEN), Université Laval, Pavillon Abitibi-Price, Room 1232, 2405, rue de la Terrasse, Québec, QC, G1V 0A6, Canada d DBBE-FCEN, Universidad de Buenos Aires – IBBEA (UBA-CONICET), Buenos Aires, Argentina article info abstract Article history: PASADO is a multidisciplinary Potrok Aike Sediment Archive Drilling prOject, which was conducted from 2008 to Received 27 February 2014 2013, focusing on the sedimentary record of the volcanic crater maar Laguna Potrok Aike (52°S, 70°W, 116 m asl) Received in revised form 24 February 2015 in southern Patagonia, Argentina. It represents one of the few non-glacial and extra-Andean sediment archives Accepted 6 March 2015 studied so far on the continental landmass between subtropical South America and Antarctica that covers the Available online 14 March 2015 entire Holocene and the Late Glacial. In this study, a high-resolution diatom analysis of the Late Glacial time interval situated between 15.60 and 10.51 ka cal. BP was performed on the PASADO sediment core. This period Keywords: Paleolimnology is of particular interest as it encompasses the Antarctic Cold Reversal (ACR), as well as the Younger Dryas (YD) Diatom analysis chronozone. To better refine the variability of environmental and climatic conditions of this Late Glacial time in- Microsedimentological analysis terval, we combined our data with those of a microsedimentological analysis conducted on the same sediments Late Glacial–Early Holocene and for the same period to infer changes in lake level and water column stratification. Our study revealed that Southern Hemisphere Westerly Winds (SWW) diatoms are an ideal proxy to complement microsedimentological analyses by providing important independent Paleoclimate information on the past limnological dynamics of Laguna Potrok Aike and the paleoclimatic conditions that prevailed during the Late Glacial in the study area and allows a new way of explaining shifts in the position of Southern Hemisphere Westerly Winds (SWW) during the Late Glacial. Peaks of planktonic diatoms, particularly Cyclostephanos patagonicus, correspond to previously detected total organic carbon (TOC), Ca/Si, Ca and Mn peaks and support the hypothesis that relatively high lake levels and weaker SWW have prevailed during the Late Glacial. Moreover, a cyclic pattern, observed both in the biological and geochemical indicators, suggests at least five shifts in the position of the SWW from the beginning of the ACR to the end of the YD. The periodicity of these shifts seems to be related to Antarctic ice-sheet discharge (AID) events in the Scotia Sea that coincide with enhanced iceberg flux from the Antarctic ice-sheet. © 2015 Elsevier B.V. All rights reserved. 1. Introduction remains still unclear, but also the signal for a YD event (glacier advance, climate cooling) is less evident and more contradictory in records at lat- The Late Glacial interval, corresponding to the last deglaciation itudes south of 49°S in Patagonia (Sugden et al., 2005; Kaplan et al., periods, contains several abrupt climate change events, such as the 2008). According to Blunier et al. (1997), the ACR precedes the YD Antarctic Cold Reversal (ACR) from 14.80 to 13.00 ka cal. BP as defined cold event by at least 1.80 ka, suggesting that the climates of the North- by Pedro et al. (2011), and the Younger Dryas chronozone (YD), from ern and Southern Hemispheres were in anti-phase during the YD. Now- 12.70 to 11.60 ka cal. BP as established by Lowe et al. (2008). Not only adays, variations in the strength and the position of the Southern the nature of climate dynamics throughout the ACR in Patagonia Hemisphere Westerly Winds (SWW) are considered to be an important feature of the global- and hemispheric-scale climate changes since the Last Glacial Maximum (LGM) (Toggweiler et al., 2006; Anderson et al., ⁎ Corresponding author. Tel.: +1 418 656 2131x5809. 2009; Denton et al., 2010; Moreno et al., 2010). Furthermore, changes E-mail addresses: [email protected] (C. Zimmermann), in the strength and/or position of the SWW modify the upwelling of [email protected] (G. Jouve), [email protected] (R. Pienitz), CO -rich deep waters around Antarctica (Le Quéré et al., 2007; Sigman [email protected] (P. Francus), [email protected] (N.I. Maidana). 2 1 Tel.:+14186543780. et al., 2010). Southern South American lakes between latitudes 51 and 2 Tel.: +1 418 656 2131x7006. 55°S, are situated between the southern limit of the SWW belt of the http://dx.doi.org/10.1016/j.palaeo.2015.03.006 0031-0182/© 2015 Elsevier B.V. All rights reserved. C. Zimmermann et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 427 (2015) 20–31 21 Last Glacial period (Ledru et al., 2005), and the current southern limit is of particular interest as it encompasses the ACR, as well as the YD of the SWW belt (Hodgson and Sime, 2010; Lamy et al., 2010; chronozone. McGlone et al., 2010). However, the comparison of records often reveals To better refine the variability of environmental and climatic con- inconsistencies or opposite conclusions, which appear to be related to a ditions of this Late Glacial time interval, we combined our data with weakness in the understanding of the proxy and/or unavailability of those of a microsedimentological analysis that Jouve et al. (2013) modern calibration datasets (Kilian and Lamy, 2012). Yet, the compre- performed on the PASADO composite profile for the same period hension of past and current variations of the SWW position and intensi- (15.60–10.51 ka cal. BP). They have shown that microsedimentological ty remains an open question (Kohfeld et al., 2013). Therefore, data can be biased by external inputs which, however, have no influ- reconstructing hydroclimatic conditions during the last deglaciation in ence on diatoms. For example, micropumices (small volcanic debris of Southern Patagonia, and especially during sudden climate changes, highly microvesicular pyroclastic glass with very thin, translucent bub- improves our understanding of the Southern Ocean's role as a source ble walls of extrusive igneous rock) have the potential to significantly or a sink of the atmospheric carbon dioxide. influence the chemical composition of sediments (e.g. iron (Fe), titani- This study is part of the international and multidisciplinary Potrok um (Ti), total organic carbon (TOC), water content (WC)) (Jouve et al., Aike Sediment Archive Drilling prOject (PASADO) which was conducted 2013). The presence of micropumices could either be linked to the from 2008 to 2013, focusing on the sedimentary record of the volcanic 1.5 m of remobilized tephra and/or the Reclus eruption around crater lake (maar) Laguna Potrok Aike (52°S, 70°W, 116 m asl) 16 ka cal. BP (Haberzettl et al., 2007; Jouve et al., 2013). Therefore, it (Zolitschka et al., 2013). The maar is situated in the Pali Aike Volcanic was impossible for Jouve et al. (2013) to relay to the TOC for any Field in the Province of Santa Cruz, southern Patagonia, Argentina, and paleoenvironmental reconstructions for the period from 15.58 to represents one of the few non-glacial and extra-Andean sediment ar- 13.64 ka cal. BP or to use Ti and Fe as paleohydrological and paleowind chives studied so far on the continental landmass between subtropical intensity proxies for the time interval between 15.20 and 11.80 ka cal. South America and Antarctica that covers the entire Holocene and the BP. Late Glacial (Zolitschka et al., 2013). In this paper, we used diatoms as a proxy to complement these Prior to PASADO, the first high-resolution multi-proxy microsedimentological analyses with the aim of providing novel and in- paleoenvironmental records from Laguna Potrok Aike have been inves- dependent information on the past limnological and ecological struc- tigated within the framework of the interdisciplinary SALSA (South ture and dynamics of crater lakes like Laguna Potrok Aike. More Argentinean Lake Sediment Archives and Modeling) project. During specifically, we inferred changes in the lake level and water column field campaigns in 2002 and 2003, sediment cores were retrieved stratification of Laguna Potrok Aike that relate to past wind conditions from the maar and combined to an 18.92 m long composite profile cov- in southern Patagonia. ering the last 16 ka cal. BP (Haberzettl et al., 2007). Using these cores, Massaferro et al. (2013) performed diatom and chironomid analyses 2. Regional setting for the whole profile, reconstructing lake level fluctuations and climate changes based on 174 samples with an average resolution of 8 to 16 cm Laguna Potrok Aike (51°57.337′ S, 70°22.688′ W, 116 m asl) is a vol- along the core. Haberzettl et al. (2005) retraced climatically induced canic maar lake located in the Pali Aike Volcanic Field in the Province of lake level changes for the last 2000 years using a multi-proxy approach Santa Cruz, southeastern part of Patagonia, Argentina (Zolitschka et al., (pollen, diatom, geochemical, isotopic, geophysical and XRF-scanning 2006, 2013)(Fig. 1). Climatically, it belongs to the semiarid Patagonian elemental analyses), while Haberzettl et al.