Multiproxy Record of Holocene Paleoenvironmental Change, Tierra del Fuego, Argentina

BORROMEI, A.M.; CORONATO A.; FRANZEN L.; PONCE J.F.; LÓPEZ SÁEZ, J.A.; MAIDANA, N; RABASSA J.; CANDEL, M.S.

PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY

Elsevier Science Ldt.

Lugar: Amsterdam; Año: 2010 vol. 286 p. 1 - 16

0031-0182

We interpret Holocene environmental conditions in a subantarctic high Andean valley from palynologicaland diatom analysis, peat stratigraphy, and local geomorphology. The multiproxy data from Las Cotorrasmire (54° 41′ 13″ S; 68° 02′ 51″ W; 420 m a.s.l.) indicate the development of a soligenous mire, as a result ofa fine grained tephra layer deposition over the mineral soils sometime prior to 8000 cal yr BP. Thepaleoecological conditions in the mire after 8000 cal yr BP show a rapid succession from a limnic to atelmatic stage as the mire is colonized by sedges (Cyperaceae) and herbaceous communities. The uplandvegetation changed from cushion and shrub heaths to an expansion of Nothofagus forest at high altitudesafter 6500 cal yr BP. The peat is interbedded with clastic sediment that originates from mass wasting eventsor floods. These depositional changes affected the mire ecosystem water-table level and nutrient status(oligotrophic and/or eutrophic conditions). Maxima in total pollen influx at about 2800, 1100 and 700 cal yrBP coincide with heightened mineral flux, and these changes are related to precipitation and slope processes.The major vegetational change registered in the pollen record is the decline of Nothofagus pollen after1000 cal yr BP, which reaches a minimum between ca. 680 and 300 cal yr BP. This minimum was likelycaused by cool, wet conditions that coincided with the Little Ice Age (LIA) in the Southern Hemisphere. Ourresults indicate the sensitivity of subantarctic Nothofagus forest and mire ecosystems to changes during theHolocene.