Magnetismo y cambios ambientales en registros terrestres: El lago de Marboré, Parque Nacional de Ordesa y Monte Perdido (Huesca)

Abstract

The study of the magnetic properties and their variations with time in lacustrine sediment cores allow deducing paleoenvironmental changes in the last millennia. This study presents a multiproxy approach that integrates geochemical, sedimentological and magnetic properties records from a long core (~6 m) of the Marboré Lake at 2500 m. a.s.l. in the West-central Pyrenees. The core spans over the last 12.7 ky cal BP. Facies, geochemical composition and magnetic properties clearly identify sedimentological environments with a great glaciar influence from 12.7-11.7 ky cal BP, including the Youger Dryas. These colder periods (YD) are characterized by a lower content in ferromagnetic minerals s.l. The beginning of the Holocene is marked by a slightly increase in the lake bioproductivity. During 9.2- 4.1 ky cal BP the increase in bioproductivity, higher content of detrital carbonates and a general decrease in the concentration and variety of the ferromagnetic s.l. minerals are coherent with a more humid period. The transition ca. 5-4.5 ky cal BP is the most significant change during the whole Holocene and it is characterized by an increase in the ferromagnetic minerals s.l., a decrease in TOC and detrital carbonates, which are interpreted as a response to an increase of aridity

Keywords

• magnetismo ambiental, sedimentologia lacustre, geoquimica inorganica, pirineos, holoceno,