|
|||||
|
|
Palynological evidence for the astronomical origin of lignite-detritus sequence in the Middle Pleistocene Marathousa Member, Megalopolis, SW Greece |
|
| Authors: | M Okuda N van VugtT Nakagawa M IkeyaA Hayashida Y YasudaT Setoguchi |
| Institution: | a Natural History Museum and Institute, Chiba, 955-2 Aoba, Chiba 260-8682, Japan b Paleomagnetic Laboratory ‘Fort Hoofddijk’, Faculty of Earth Sciences, Utrecht University, Budapestlaan 14, 3584 CD Utrecht, The Netherlands c International Research Centre for Japanese Studies, Kyoto 610-1192, Japan d Department of Earth and Space Science, Graduate School of Science, Osaka University, Osaka 560-0043, Japan e Science and Engineering Institute, Doshisya University, Kyo-tanabe 610-0321, Japan f Department of Geology and Mineralogy, Division of Earth and Planetary Sciences, Kyoto University, Kyoto 606-8224, Japan |
| Abstract: | The Marathousa Member, Middle Pleistocene strata in the fluvio-lacustrine Megalopolis basin, southwest Greece, displays distinct but complicated lithological cycles comprising first-order alternation of lignites and detrital muds and second-order alternation expressed by frequent intercalation of organic layers. Palynological evidence indicates that the lithological cycles are driven by the Earth’s orbital forcing. All the lignite seams yield temperate oak forest whereas the detrital beds provide semi-arid steppe mainly of Artemisia. This means that the first-order lithological cycle represents the glacial/interglacial cycle (i.e., the 100-kyr eccentricity cycle), providing a timescale of at least 350 kyr to the Marathousa Member. Pollen also detects smaller-scale climate fluctuations in many of the subordinate organic layers, with the total number of fluctuations being five in a complete lignite-detritus couplet. This means that the second-order lithological cycle reflects the 21-kyr insolation cycle. A tentative phase relation between the lithological cycles and the astronomical cycles is shown based on palynostratigraphy and electron spin resonance dating. Lacustrine environments with increased water tables are implied for the glacial periods sedimentologically, in contrast to local swamp vegetation for the interglacial periods. The subordinate organic layers were formed under intermediate environments (climate, water depth, etc.) between full glacials and interglacials. |
| Keywords: | orbital forcing Middle Pleistocene Greece palynology EPR spectra age climate change |
| 本文献已被 ScienceDirect 等数据库收录！ | |