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Late Pleistocene to Holocene palaeoenvironmental variability in the north‐west Spanish mountains: insights from a source‐to‐sink environmental magnetic study of Lake Sanabria
Author(s) -
BORRUELABADÍA VIOLETA,
GÓMEZPACCARD MIRIAM,
LARRASOAÑA JUAN C.,
RICO MAYTE,
VALEROGARCÉS BLAS,
MORENO ANA,
JAMBRINAENRÍQUEZ MARGARITA,
SOTO RUTH
Publication year - 2015
Publication title -
journal of quaternary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.142
H-Index - 94
eISSN - 1099-1417
pISSN - 0267-8179
DOI - 10.1002/jqs.2773
Subject(s) - geology , holocene , fluvial , younger dryas , greigite , geochemistry , outwash plain , sediment , glacial period , moraine , environmental magnetism , pleistocene , magnetic mineralogy , sink (geography) , geomorphology , paleontology , structural basin , pyrite , cartography , geography , physics , magnetization , quantum mechanics , magnetic field , remanence
We present a source‐to‐sink environmental magnetic study of a sediment core from Lake Sanabria (north‐west Iberian Peninsula) and rocks of its catchment. The results indicate the occurrence of magnetite, and probably also pyrrhotite, in sediments accumulated between ca. 26 and 13 cal ka BP in a proglacial lake environment. These minerals also appear to dominate the magnetic assemblage of Palaeozoic rocks from the lake catchment. This indicates that sedimentation was then driven by the erosion of glacial flour, which suffered minimal chemical transformation due to a rapid and short routing to the lake. A sharp change in magnetic properties observed in the lake sediments between 13 and 12.6 cal ka BP reflects the rapid retreat of glaciers from the lake catchment. Sediments from the upper half of the studied sequence, accumulated after 12.6 cal ka BP in a lacustrine environment with strong fluvial influence, contain magnetite and smaller amounts of maghemite and greigite. We suggest that greigite grew authigenically under anoxic conditions caused by enhanced accumulation of organic matter into the lake. The occurrence of maghemite in these sediments suggests pedogenic activity in the then deglaciated lake catchment before the erosion and transportation of detrital material into the lake.