The magnetostratigraphy and rock-magnetism of the Paleocene-Eocene interval has been studied in the recent years in several Tethyan marine sections of the Belluno Basin of NE Italy (Possagno, Cicogna, South Ardo, Alano). The paleomagnetic results, integrated with calcareous nannofossil biostratigraphy, allowed the recovery of a virtually continuous ~27 Myr-long interval of time spanning from the K/Pg boundary (~65 Ma) at the South Ardo section up to the middle-late Eocene boundary (~38 Ma) at the Alano GSSP candidate, and bracketing some of the most extreme climate conditions of the Cenozoic such the Early Eocene climatic optimum (EECO) and the Paleocene-Eocene thermal maximum (PETM). The rock-magnetic data indicate that the magnetic mineralogy of the sediments generally consists of variable proportions of magnetite-maghemite-hematite, which are iron oxides characterized by different oxidation states and crystal structures. We reconstructed the rock-magnetic variability across the investigated interval, and placed it on a temporal reference frame using a CK95-based age-depth function for comparison with oxygen isotope data from the literature. The rock-magnetic data indicate that relatively warmer climate periods (i.e. the PETM and the early Eocene warming trend leading to EECO) are associated with high contents of detrital hematite relative to magnetite-maghemite, while relatively cooler climates (i.e. the Paleocene) are associated with a relative increase in magnetite-maghemite. We speculate that the increase of detrital hematite observed during warm periods is due to intensified chemical weathering rates of land silicates under warm and humid climates. We therefore show that rock-magnetic properties can be useful proxies to study the efficiency of the silicate weathering negative feedback mechanism to stabilize long-term Earth's surface temperatures.
|Titolo:||Paleocene-Eocene magnetostratigraphy and climate-driven rock-magnetism from the Belluno Basin (Italy)|
MUTTONI, GIOVANNI (Primo)
|Data di pubblicazione:||dic-2012|
|Settore Scientifico Disciplinare:||Settore GEO/02 - Geologia Stratigrafica e Sedimentologica|
|Citazione:||Paleocene-Eocene magnetostratigraphy and climate-driven rock-magnetism from the Belluno Basin (Italy) / G. Muttoni, E. Dallanave. ((Intervento presentato al convegno American Geophysical Union tenutosi a San Francisco nel 2012.|
|Appare nelle tipologie:||14 - Intervento a convegno non pubblicato|