Abstracts VIII Southern Connection Congress 2016 (2)

THE APPLICATIONS OF TEPHROCHRONOLOGY FOR ENHANCING PALEOENVIRONMENTAL RECONSTRUCTIONS IN CONO SUR 

ALLOWAY, BRENT1 , MORENO, PATRICIO2 , 1 School of Geography, Environment & Earth Sciences Victoria University of Wellington.2 Department of Ecological Sciences and Millennium Institute of Ecology and Biodiversity Universidad de Chile. 

Ongoing tephra studies in Southern Chile and Argentina (Cono Sur) are currently focused on two important aspects: 1) Elucidating eruptive records and assessing associated hazards for a particular volcano, and 2) Utilisation of tephra as a chrono-stratigraphic marker in wide-ranging Quaternary paleoenvironmental studies. Recent Andean eruptions (i.e. Puyehue-Cordon Caulle (2011), Chaiten (2008/9) and Hudson (1971/91)) have all clearly shown that hazards associated with these eruptions not only pose a risk to adjacent communities but also that ash-fall (tephra) can be quickly distributed over exceptionally large areas and pose a significant and wide-ranging hazard to civil aviation, agriculture and communities located distally. Since a tephra can be extensively distributed through the landscape in a geological instance of time, its value as an isochronous-stratigraphic tool has increasingly been recognised to the point where tephra are now routinely utilised in diverse paleoenvironmental research that focus on high-resolution lake, glacial and marine records. The construction of such records in Cono Sur is fraught with difficulties including: mineralogy and weathering susceptibility that impedes geochemical characterization as well as, pervasive and repeated Andean glaciation that has removed and/or obscured older tephra records. In this presentation, we will provide a number of examples from Cono Sur, where despite these limitations, the utility of tephra can still be clearly demonstrated to assist with the assessment of eruptive records and associated hazards but also, the correlation of equivalent-age sequences for paleoenvironmental comparisions – something of which has great relevance to this forum.   

(Sponsored by a Victoria University of Wellington Science Faculty Research Grant (to BVA); Chilean Fondecyt 1151469 and ICM Grants P05-002 and NC120066 (to PIM)) 

THE UTILITY OF TEPHROCHRONOLOGY TO PALEOENVIRONMENTAL STUDIES: EXAMPLES FROM EQUATORIAL ASIA, TROPICAL AUSTRALIA AND SOUTHERN MID-LATITUDE NEW ZEALAND AND CHILE

 ALLOWAY, BRENT1 , School of Geography, Environment & Earth Sciences (SGEES), Victoria University of Wellington. 

Tephra is an all-embracing term for the explosively erupted, loose fragmental (pyroclastic) products of a volcanic eruption. The term tephra includes fall deposits (commonly called tephra-fall or tephra fallout) and unconsolidated deposits derived from pyroclastic flows or surges. Tephra deposits have two special features: (1) they are erupted and deposited over very short time periods, geologically speaking, usually a matter of only hours or days to perhaps weeks or months; and (2) they can be spread widely over land and sea to form a thin blanket that (unless reworked) has the same age wherever it occurs. Once a tephra is recognised and dated, it has the ability to effectively connect equivalent-aged sequences in a variety of terrestrial to marine environments wherever it is found. On this basis, tephrochronology has tremendous utility for a wide variety of paleo-environmental studies particularly in, and adjacent to, volcanic regions. In this presentation I will outline ongoing work in Flores, Indonesia, where tephras have been essential for determining the timing of initial human colonisation to the region, as well as the potential speciation from H. erectus to H. floresiensis. I will also show the potential of utilising tephra in long-sediment records retrieved from tropical Australia even though the tephras themselves are not locally sourced. Finally, I will talk about the applications of tephra in paleoenvironmental studies taking place in southern mid-latitude NZ and Chile – countries with similar geological settings and which are more closely connected in a paleoenvironmental sense than one could possibly imagine.

 (Sponsored by Victoria University of Wellington Science Faculty Research Grant and Chilean Fondecyt Grant 1151469) 

CLIMATE VARIABILITY, TREE-GROWTH AND DEMOGRAPHIC PATTERNS IN A NOTHOFAGUS PUMILIO TREELINE ECOTONE FROM NORTHERN PATAGONIA

 ALVAREZ, CLAUDIO1,2, CHRISTIE, DUNCAN 2,1, VELASQUEZ-ALVAREZ, GONZALO2 , VEBLEN, THOMAS3 , 1 Center for Climate and Relience Reseearch (CR)2, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile2 Laboratorio de Dendrocronologia y Cambio Global, Facultad de Ciencias Forestales y Recursos Naturales, Universidad Austral de Chile.3 Biogeography Lab, Department of Geography, University of Colorado Boulder. 

Our research examines the relationships between climate variability and tree growth, and the potential colonization of tree individuals above the present treeline in a Nothofagus pumilio forest at the Choshuenco volcano (40o S) in the northern Patagonian Andes. Based on treeline control theory which indicates that the low temperatures determines the altitudinal position worldwide, we would expect a temporal increment in the establishment of N. pumilio above the present treeline as a result of increasing temperatures in the Andes of northern Patagonia. We address the following questions: 1) are the temporal patterns of climate (temperature and precipitation) influencing the establishment of N. pumilio above the present treeline? 2) If so, is the relation between tree establishment and climate conditions the same than tree-growth and climate? To answer these questions, we dated the establishment of seedlings, saplings and small trees of N. pumilio (n=664) collected above the present adult treeline. Preliminary results indicate that the N. pumilio establishment above treeline has been continuous over the last three decades. This period coincide with an increase of temperatures, decrease of precipitation and a decrease on tree growth at the adult forest in the treeline. This finding would indicates that responses of tree growth and treeline advance to climatic conditions were not similar at the Choshuenco volcano, and it supports the idea that temperatures increase and precipitation decrease in northern Patagonia may be producing a successful establishment of N. pumilio above treeline but decreasing tree growth. 

(Sponsored by FONDAP1511009, FONDECYT 1120965) 

CROSS-TAXONOMIC INSIGHTS FROM BIOGEOGRAPHICAL ANALYSES, AND THE INTERPLAY BETWEEN TEMPERATE AND TROPICAL ZONES 

ANTONELLI, A1 , ZIZKA, ALEXANDER1 , Department of Biological and Environmental Sciences, Faculty of Sciences, University of Gothenburg. 

No single taxon gives a pattern: the historical assembly of the world’s biomes can only be inferred through cross-taxonomic analyses. In this talk we will present our recent work in ‘comparative biogeography’, focusing on i) data-driven identification and delimitation of biogeographical regions instead of opiniongenerated classifications; ii) spatial coding of species into regions and altitudinal ranges for biogeography and macroecology; and iii) the estimation of historical range shifts and region-specific diversification. Our studies indicate that the application of network methods on species occurrence data can extract considerably stronger biogeographical signal than hitherto realized; that bioinformatic tools are able to provide rapid assessments of biodiversity patterns; that Neotropical angiosperms have speciated and gone extinct at significantly higher rates than in other tropical regions; that the Great American Biotic Interchange occurred millions of years earlier than assumed; and that fossils play a major role in reducing uncertainties in biogeographical analyses. Tropical America has acted as a species pump to the rest of the world, but it also received considerable input from temperate regions in South and North America. Likewise, the tropical and temperate Andes have exchanged a substantial amount of plant and animal lineages with Amazonia in the last 30 million years, with peaks correlating in time with major phases of mountain uplift. These examples showcase how old questions can be addressed by new methods and more data, and identify future directions in biogeographical research. 

HOLOCENE VARIATIONS IN PRODUCTIVITY ASSOCIATED WITH CHANGES IN GLACIER ACTIVITY AND FRESHWATER FLUX IN THE CENTRAL BASIN OF THE STRAIT OF MAGELLAN 

ARACENA, C1 , KILIAN, ROLF2 , LANGE, CARINA6 , BERTRAND, SEBASTIEN3 , LAMY, FRANK4 , ARZ, HELGE5 , DE POL-HOLZ, RICARDO6 , BAEZA, OSCAR2 , PANTOJA, SILVIO6 , KISSEL, CATHERINE7 , 1 Instituto de Ciencias Marinas y Limnologicas, Ciencias, Universidad Austral de Chile.2 Lehrstuhl fur Geologie, Fachbereich VI, Geowissenschaften, Universitat Trier, University of Trier.3 Renard Centre of Marine Geology, Sciences, University of Gent.4 Am Alten Hafen 26, 27568 Bremerhaven, Germany AWI.5 Marine Geology, Seestrasse 15, D 18119 Rosto Leibniz Institute for Baltic Sea Research Warnemundeck.6 Department of Oceanography, Faculty of Science, University of Concepción.7 Av de la Terrasse, 91198 Gif-sur Yvette Cedex, France Lab. Sc. Climat et de l Environnement/IPSL. 

One of the most important factors controlling fjord primary production in southernmost Patagonia is the variability in the thermohaline structure of the water column. In the present day environment, thermal stratification is related to freshwater input and in particular to the seasonal melting of glaciers. Here we assess whether this relation between fjord productivity and freshwater input holds true for the Holocene, using a sediment record from the central basin of the Strait of Magellan (MD07-3132, 53 ◦44.17’S; 70 ◦ 19.03’W). Our approach relies on a proxy based reconstruction of fjord sea surface temperature (SST), paleosalinity, freshwater input, and paleoproductivity. The results indicate that, during the early Holocene, productivity was low (accumulation rates of marine organic carbon (AR marOC) (≦ 20 kg m−2 kyr−1), likely due to high freshwater contribution resulting in low salinity and low SSTs. After 8.5 kyr BP and during the mid and late Holocene all the productivity proxies increase. The AR marOC (˜30 kg kg m−2 kyr−1), CaCO3 (˜60 kg kg m−2 kyr−1) and opal (425 kg kg m−2 kyr−1) reached the highest values during the last millennium. This increase was probably driven by the marine transgression during which marine macronutrient-rich waters entered into the central basin. The late Holocene rise in productivity was interrupted by a low salinity phase between 3.2 and 2.2 kyr BP, during which productivity returned to early Holocene conditions in response to increased input of glacial clays from Cordillera Darwin, as suggested by high values of K/Si ratio (˜1.2).

 (Sponsored by PROYECTO DID-UACh S-2015-28)