Charles Darwin and the oLdest Glacial events in Patagonia: The Erratic blocks of the río santa Cruz valley

Although the depositational environment assigned by Darwin to the large erratic blocks and gravels in the Río Santa Cruz valley has been reinterpreted, his geomorphological and stratigraphic observations are still in force. The large erratic blocks he described as crowning the Condor Cliff terrace and spread at the bottom of the valley just east of this locality (Sites 2 and 3), are now interpreted as indicators of the maximum glacial expansion in Patagonia. Similar blocks, though of a different lithology, accumulated over a lower terrace located up-valley (Site 4), are now linked to moraines and glacifluvial terraces of the Penultimate Glaciation. Finally, in addition to the erratic block discovered by Darwin in the lower Río Santa Cruz valley (Site 1), there are others - recently discovered - which probably account for a catastrophic event ascribed to a big glacier-lake outburst during the last interglacial.Fil:Strelin, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Malagnino, E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Reconstruction of the late quaternary glacial geology on King George Island, South Shetland Islands: First steps of a geoscientific project

King George Island (Isla 25 de Mayo) is the largest one of the South Shetland Islands (SShI). This archipelago is located approximately 120 km NW of the Antarctic Peninsula, from which it is separated by the Bransfield Strait (Mar de la Flota). The SShI are located just south of the Antarctic Convergence Zone in a key location for investigating glacial and climatic fluctuations relative to both the Southern Hemisphere and the rest of Antarctica. The geomorphology and glacier geology of the SShI (Sugden and John 1973, Hall 2003 and 2007, Del Valle et al. 2007, Strelin 2010, Simms et al. 2011) constitutes a fragmentary record. Despite the deglaciation, inland ice free areas are scarce and are strongly affected by the thaw with the consequent destruction of previous geoforms. The few obtained radiocarbon ages on land exposures have poor stratigraphic control being necessary to consider the problems of pollution and the reservoir effect that affect them. Based on geochemical and sedimentological proxies and radiocarbon dating in sedimentary cores obtained from bays, some glaciers advances and warm periods have been inferred for the middle and late Holocene, among them are those corresponding to the Medieval Climate Optimum and the Little Ice Age (LIA) (Yoon et al. 2000 and 2004, Hass et al. 2010, Monien et al. 2011). It should be noted that for some glaciological reconstructions based on organic radiocarbon dating on marine sediments the ages are still questionable. Often it does not exist yet a clear criteria of correlation that allow to link between glaciterrestrial sediments and glacimarine ones. The study of the glacial, periglacial and coastal marine record of King George Island has a particular importance to enhance the knowledge of its paleoenvironmental evolution since the Marine Isotopic Stage 3 (MIS 3). There is no precision on the beginning and end of the Last Glacial Maximum (LGM), nor on the rhythm of the deglaciation post-LGM, known as Termination 1, both for coastal and marine areas, as well as offshore areas from King George Island. In the same way, it´s not known if there was a glacial advance linked with the Antarctic Cold Reversal clearly detectable in Antarctic ice cores or sediment deposits in southern Patagonian exposures (Strelin et al. this congress). The way in which the deglaciation continued during the early Holocene, the peak of the Holocene marine transgression (Strelin et al. this Congress), the later chronology of the Neoglacial advances, including the LIA, and the warmer periods that separate them are as well topics to deepen. The objective of this project is to study and date the geomorphological and glaciterrestrial evidences linked to the glacial history in the area of South Shetland Islands, since MIS 3, correlate them with bathymetric records and proxies from marine cores and discuss its link with other sectors of the Antarctic Peninsula, particularly with James Ross Islan

Exploring the ontogenetic scaling hypothesis during the diversification of pollination syndromes in <i>Caiophora</i> (Loasaceae, subfam. Loasoideae)

Phenotypic diversification of flowers is frequently attributed to selection by different functional groups of pollinators. During optimization of floral phenotype, developmental robustness to genetic and non-genetic perturbations is expected to limit the phenotypic space available for future evolutionary changes. Although adaptive divergence can occur without altering the basic developmental programme of the flower (ontogenetic scaling hypothesis), the rarity of reversion to ancestral states following adaptive radiations of pollination syndromes suggests that changes in the ancestral developmental programme of the flower are common during such evolutionary transitions. Evidence suggests that flower diversification into different pollination syndromes in the Loasoideae genus Caiophora took place during a recent adaptive radiation in the central Andes. This involved transitions from bee to hummingbird and small rodent pollination. The aim of this work was to examine if the adaptive radiation of pollination syndromes in Caiophora occurred through ontogenetic scaling or involved a departure from the ontogenetic pattern basal to this genus.Fil: Strelin, Marina Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Benitez-Vieyra, Santiago Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Fornoni, Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina. Universidad Nacional Autónoma de México; MéxicoFil: Klingenberg, Christian Peter. University of Manchester; Reino UnidoFil: Cocucci, Andrea Aristides. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin

What is the real isotopic signature of dust emitted from Tierra del Fuego?

Fil: Gaiero, D.M. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Gili, S. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Strelin, J. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Strelin, J. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Antártico Argentino; Argentina.Fil: Koestner, E. IG-UFRGS. Laboratório de Geología Isotópica; Brasil.Fil: Chemale Jr, F. IG-UFRGS. Laboratório de Geología Isotópica; Brasil.Sugden et al. (2009) suggested an on/off switch mechanism that could explain the 20 times increase of dust deposition in Antarctica during the Last Glacial Maximum (LGM), as compared to present day. This suggested switch resides in Patagonian pro-glacial lakes; when glaciers retreat sediments are deposited in the lakes and dust emission ceased in opposition to cold periods, when glacial pour out sediments to the outwash plain, then increasing dust emission. The on/off switch mechanism proposed is supported on age analyses and strontium (Sr) and neodymium (Nd) isotope ratios of ancient lacustrine sediment samples from the Magellan Strait (MS) and from the North Patagonian icefield (NPI). The lacustrine sediments were used as representative of sediments that were disgorged to the outwash plain during the LGM. We argue on the type of samples used to characterize the possible Patagonian outwash sediments deflated during the LGM and accordingly, on the interpretation of the source of this dust. Modern sediments are deflated from the Patagonian surface mainly from widespread ephemeral lakes (Gaiero 2007), which are sporadically refilled with sediments supplied from the surrounding areas mainly through water runoff. The aim of this contribution is to discuss about this and contrast data from both set of samples and discuss about their significance for the interpretation of the isotopic signatures recorded on the sedimentary archives of the Southern Hemisphere (e.g., Antarctic ice cores). Fig. 1 shows that the mean isotopic composition of dry lake sediments (collected from the ancient outwash plain in the San Sebastián Bay area) and dust collected at Río Grande are significantly different compared to MS samples and very similar to sediments representing the Fuegian continental shelf (Basile et al. 2007). Similar to modern dust released from continental Patagonia (north of ~52° S), modern data from Tierra del Fuego could also be explained by a mixing between Jurassic rhyolites and Quaternary volcanic rocks (e.g., Gaiero et al. 2007; Fig. 1). On the contrary, the samples used by Sugden et al. (2009) seem to characterize discrete sources. The isotopic composition of most samples from the MS plots mostly within the compositional field corresponding to the Antarctic Jurassic rhyolites and similar rocks that outcrop out close along the Fuegian Cordillera (Gaiero et al. 2007). In the case of NPI samples, their compositions are similar to the local outcropping Paleozoic plutonic and metasedimentary rocks (Killian and Behrmann 2003). Nevertheless, directly to the W of the NPI, the isotopic composition of Pliocene/Pleistocene Chilean trench sediments (mean 87Sr/86Sr = 0.707 and &#948;Nd(0) = -2.1) indicates a variable contribution from other rocks cropping out in the area (e.g., Quaternary volcanic rocks). Why MS and NPI samples are different from modern Patagonian dust?Fil: Gaiero, D.M. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Gili, S. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Strelin, J. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Strelin, J. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Antártico Argentino; Argentina.Fil: Koestner, E. IG-UFRGS. Laboratório de Geología Isotópica; Brasil.Fil: Chemale Jr, F. IG-UFRGS. Laboratório de Geología Isotópica; Brasil.Geoquímica y Geofísic

Holocene deglaciation and glacier readvances on the Fildes Peninsula and King George Island (Isla 25 de Mayo), South Shetland Islands, NW Antarctic Peninsula

To provide insights into glacier-climate dynamics of the South Shetland Islands (SSI), NW Antarctic Peninsula, we present a new deglaciation and readvance model for the Bellingshausen Ice Cap (BIC) on Fildes Peninsula and for King George Island/Isla 25 de Mayo (KGI) ~62°S. Deglaciation on KGI began after c. 15 ka cal BP and had progressed to within present-day limits on the Fildes Peninsula, its largest ice-free peninsula, by c. 6.6–5.3 ka cal BP. Probability density phase analysis of chronological data constraining Holocene glacier advances on KGI revealed up to eight 95% probability ‘gaps’ during which readvances could have occurred. These are grouped into four stages – Stage 1: a readvance and marine transgression, well-constrained by field data, between c. 7.4–6.6 ka cal BP; Stage 2: four probability ‘gaps’, less well-constrained by field data, between c. 5.3–2.2 ka cal BP; Stage 3: a well-constrained but restricted ‘readvance’ between c. 1.7–1.5 ka; Stage 4: two further minor ‘readvances’, one less well-constrained by field data between c. 1.3–0.7 ka cal BP (68% probability), and a ‘final’ well-constrained ‘readvance’ after 1950 CE) is associated with recent warming/more positive SAM-like conditions

A case of behavioural diversification in male floral function – the evolution of thigmonastic pollen presentation

The authors gratefully acknowledge funding provided by an Else-Neumann-Stipendium (http://www.fu-berlin.de/sites/promovieren/drs/nachwuchs/nachwuchs/nafoeg.html), Deutscher Akademischer Austausch Dienst (DAAD) and botconsult GmbH at different stages of data acquisition. We thank Tobias Grass, Joana Bergmann and Franziska Weber (Freie Universität Berlin) for help with data collection in the field and in the greenhouse. Nicole Schmandt, Federico Luebert, Juliana Chacón and Dietmar Quant (Universität Bonn) provided help in the molecular laboratory and the edition of the molecular dataset. We furthermore thank Markus Ackermann (Koblenz) for providing photographs, Philipp Klein (Berlin) for editing the video and Katy Jones (Berlin) for helpful comments on an earlier version of the manuscript. Rafael Acuña has been supported by the ALECOSTA scholarship program. Coverage of the article processing charge by the German Research Foundation via the Open Access Publication Fund of the Freie Universität Berlin is gratefully acknowledged.Peer reviewedPublisher PD

Charles Darwin and the oLdest Glacial events in Patagonia: The Erratic blocks of the río santa Cruz valley

Although the depositational environment assigned by Darwin to the large erratic blocks and gravels in the Río Santa Cruz valley has been reinterpreted, his geomorphological and stratigraphic observations are still in force. The large erratic blocks he described as crowning the Condor Cliff terrace and spread at the bottom of the valley just east of this locality (Sites 2 and 3), are now interpreted as indicators of the maximum glacial expansion in Patagonia. Similar blocks, though of a different lithology, accumulated over a lower terrace located up-valley (Site 4), are now linked to moraines and glacifluvial terraces of the Penultimate Glaciation. Finally, in addition to the erratic block discovered by Darwin in the lower Río Santa Cruz valley (Site 1), there are others - recently discovered - which probably account for a catastrophic event ascribed to a big glacier-lake outburst during the last interglacial.Fil:Strelin, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Malagnino, E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Relationships between geomorphology and vegetation patterns in subantarctic andean tundra of Tierra del Fuego.

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