Dating and Interpretation of Secondary Carbonate Deposits from the Last Interglacial

• Main Author: Holzkämper, Steffen
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2004
• Subjects: 550; 550 Earth sciences; North Atlantic
• Online Access: https://archiv.ub.uni-heidelberg.de/volltextserver/4442/; https://archiv.ub.uni-heidelberg.de/volltextserver/4442/1/Dissertation.pdf; https://doi.org/10.11588/heidok.00004442; https://nbn-resolving.org/urn:nbn:de:bsz:16-opus-44427

The age of secondary carbonate deposits has been determined via U/Th dating. According to the investigation of speleothems from the high Alpine Spannagel Cave (Zillertal Alps, Austria), a first warming occurred 135,000 years (135 kyr) ago. Sinter growth was interrupted from 130 kyr to 126 kyr, suggesting, that a cooler period preceded the start of the classical Eemian. Two additional growth interruptions within the Eemian suggest an unstable progression of the Last Interglacial, which terminated at 116 kyr. Thus, the classical Eemian lasted for about 10 kyr, which is the duration the Holocene has already reached. Another speleothem from Spannagel Cave formed during several warm periods of the past 250 kyr. The timing of the growth phases can only partly be explained by northern summer insolation maxima, which are thought to be the main trigger for climatic shifts by most paleoclimate researchers. A better correspondence is achieved by comparing the growth phases with the flux of Galactic Cosmic Rays reconstructed from deep sea sediments. These are probably affecting the condensation processes in clouds and accordingly, the Earth’s energy budget and latent heat transport processes. Spectral analyses that were applied on the stable isotope profiles taken along the growth axis of a stalagmite from Spannagel Cave suggest, that the solar activity influenced Eemian climate, as the detected periodicities are similar to some well–known solar cycles. The existence of cycles with a periodicity of ~1470 years (DANSGAARD/OESCHGER–cycles) in both a stable isotope profile of a Spannagel flowstone and North–Atlantic sediments probably indicates, that the climate of Central Europe and the North–Atlantic circulation pattern are a coupled system. Stalagmites from Oman provided information about the timing and progression of the Last Interglacial in lower latitudes. Sinter growth commenced ~135 kyr ago and continued until ~116 kyr. During this period, the ITCZ has moved further to the North, so that the South Asian Monsoon could ...