Paleoclimatic characterization of Arctic Ocean sediments around the Northwind Ridge using x-ray fluorescence and visible-near infrared spectroscopy .

摘要

The Arctic Ocean sediment (AOS) is highly sensitive to global climate changes and has become a focus of much paleoclimatic research. In this study, paleoclimatic characteristics of the AOS have been studied using downcore X-Ray Fluorescence (XRF) data from 13 Healy-Oden TransArctic Expediton cores. Lithological and multi-element variations representing glacial and interglacial cycles were correlated using the variable-based Varimax-rotated Principal Component Analysis (VPCA) of the XRF data.;The Visible-Near Infrared (VNIR) derivative spectroscopy study of the sediment core P1-92AR-P25 (or P25) demonstrates cyclic variations in downcore mineralogy. VPCA of the downcore VNIR data show three mineral assemblages reflecting glacial-- interglacial cyclicity. The results are consistent with clay mineral cycles identified by previous studies (Yurco et al. 2010). The downcore mineralogical cyclicity provides a glacial--interglacial portrait of changes in sediment provenance indicative of both Laurentide and Eurasian sources and delivery mechanisms associated with changes in sea level, configurations of Arctic ice sheets and oceanic/atmospheric circulation. The study further reveals that the VNIR spectroscopy can be used as an effective tool in semi quantitative prediction of dolomites.;Wavelet analysis in component scores of 8JPC (XRF data) and P25 (VNIR data) identifies significant periodicities; eccentricity (∼100 kyr), Obliquity (∼40 kyr) and precession (∼21 kyr). In both 8JPC and P25 glacial-interglacial variations show eccentricity whereas in 8JPC, LIS changes and biogenic productivity represent precession cycles and in P25 carbonate sedimentation displays strong obliquity (∼40 kyr) cycles with moderate influence of precession (∼21 kyr) cycles probably representing IRD events in stadial/ interstadial cycles associated with Heinrich and Bond cycles. These findings agree with Adler et al., 2009 that AOS reflects insolation-controlled paleoclimatic processes with longer-term glacial cycles interrupted with abrupt iceberg/melt water discharges of both Laurentide and Eurasian sources. High resolution age control is critical for better evaluation of periodicities of paloclimatic variations.;The main components generated by the VPCA have been interpreted as related to terrigenous (erosional) sources (F1, Ti-K-Rb-Fe-Ba-Cr), changes in Laurentide Ice Sheet (LIS) (F3, Ca-P-I), pore water concentration/ biogenic productivity (F5, P-Cl-S), bottomwater ventilation (F6, Mn-Ni-Cu) and siliciclastics (F7, Sr-Zr). Component variations are well consistent with glacial ("gray beds")-interglacial("brown beds") cycles and associated deglacial carbonate pulses in the core 8JPC with identified age controls of Adler et al., 2009 and Polyak et al., 2009. Mn-rich layers (corresponding F6 peaks) of interglacial origin are generally anticorrelated with Ca pulses (F3 peaks) generated during deglaciations. Cl data show general enhancement with interglacials and glacial gray beds with coarse detrital sand pulses suggesting saline pore water trapped within the porosity of these coarser beds. Pleistocene sedimentation is characterized with only a few shallow carbonate spikes, which indicate a weakened Beaufort Gyre and stronger Transpolar Drift as indicated by the lower abundance of Laurentide material in the Eurasian Basin.