Late Quaternary climatic history of the Chilean Channels based on fossil pollen and beetle analyses, with an analysis of the modern vegetation and pollen rain

Abstract

Ashworth, A. C, Markgraf, V. and Villagran, C . 1991. Late Quaternary climatic history of the Chilean Channels based on toss11 pollen and beetle analyses, with an analysis of the modern vegetation and pollen rain. lournal ABSTRACT: Fossil beetles and pollen were examined from an intermorainal bog at Puerto Eden, lsla Wellington, Chile (latitude 49"08'S, longitude 74"25'W). Wood from near the base of the section has an age of 12 960 2 150 yr BP. Occurrence of flightless beetle species in the basal peat sample is evidence that some members of the biota survived the last glacial maximum in refugia. The assumption that the Chilean Channels were entirely ice-covered is incorrect. Plants and insects that invaded the deglaciated terrain were those of an Ernpetrum heathland in which patches of Nothofagus forest were restricted to sheltered locations. The climate supporting the heathland is inferred to have been windier and probably drier than that of the present day. From 13 000 yr BP to 9500 yr BP Nothofagus forest expanded, possibly in response to less windiness and more available moisture. Neither the fossil beetle nor pollen data support a return to significantly colder conditions between 1 1 000 and 10 000 yr BP at the time of the Younger Dryas Stade. From 9500 to 5500 yr BP the climate was as wet as that of the present day, based on an increased representation of the pollen of moorland plants and of aquatic beetle species. From 5500 to 3000 yr BP the climate was drier, as indicated by the expansion of Empetrum heath and the reduction in mesic habitats. From 3000 yr BP to the present-day mesic habitats dominated as the climate returned to a wetter mode. The alternatively wetter and drier episodes are attributed to latitudinal shifts in the position of storm tracks in the belt of Southern Westerlies. Journal of Quaternary Science

Pollen-based biome reconstructions for Latin America at 0, 6000 and 18 000 radiocarbon years ago

“…This cold, arid environment is clearly reproduced by the vegetation which shows a transformation from the cool temperate rain forest to the cool grass/shrubland biome. Although Nothofagus-dominated forest is thought to have been extirpolated from coastal Chile at the LGM (Hollis and Schilling, 1981), fossil beetle assemblages in basal peat from Puerto Eden (49 • S, 74 • W) indicate that Nothofagus-dominated forest survived glaciation within the Chilean channels (Ashworth et al, 1991). An earlier date of deglaciation of the Taitao Peninsula indicates there was relatively local migration from Chiloé Island that may explain the rapid re-growth of Nothofagus-dominated forest (Lumley and Switsur, 1993).…”

Estimating Neotropical palaeotemperature and palaeoprecipitation using plant family climatic optima

“…Ninety-five sites in Central and South America are available online. Of these, sixteen sites are found below 390 m in elevation and have recent surface sediments (< 100 14 C yr BP) (Godley andMoar, 1973 Markgraf, 1980;Markgraf, 1983;Mercer and Ager, 1983;Markgraf, 1989 Byrne andHorn, 1989;Ashworth et al, 1991;Markgraf, 1991;Graf, 1992Markgraf, 1993Schabitz, 1994;Vandevender, 1995 Behling, 1995a;Behling, 1995b;Behling, 1996;Leyden et al, 1996). These were used to test the accuracy of the model.…”

Scale analysis of carabids richness (Coleoptera: Carabidae) in southern South America

“…Other factors that could have contributed to carabids dispersion were the glacio-eustatic changes in sea level during quaternary. For instance, during LGM the lower sea level exposed the shelf around the Pacifi c Patagonian fjords (Ashworth et al 1991) and later, postglacial isostatic rebound caused land mass elevations along shoreline terraces (Stern et al 2011). Therefore, such areas probably served as land bridges allowing the movement of carabid beetles among the mainland and islands.…”

“…Migadopini, Ceroglossini), monotypic genera and species with relict distribution (Darlington 1965). These insects are good indicators of past terrestrial environments (Elias 2007), since they are highly mobile and thereby able to respond rapidly to environmental change by rapidly shifting its distribution patterns; they are also very abundant and have a well-preserved fossil record, since it is feasible to fi nd almost all current species in ensembles of the Quaternary (Ashworth et al 1991;Ashworth 2007). …”