Abstract
Abstract. Gamma ray (GR) fluctuations and potassium (K) values from downhole logging data obtained in the sediments of Lake Ohrid from 0 to 240 m below lake floor (b.l.f). correlate with fluctuations in δ18O values from the global benthic isotope stack LR04 (Lisiecki and Raymo, 2005). GR and K values are considered a reliable proxy to depict glacial–interglacial cycles, with high clastic input during cold and/or drier periods and high carbonate precipitation during warm and/or humid periods at Lake Ohrid. Spectral analysis was applied to investigate the climate signal and evolution over the length of the borehole. Linking downhole logging data with orbital cycles was used to estimate sedimentation rates and the effect of compaction was compensated for. Sedimentation rates increase on average by 14 % after decompaction of the sediment layers and the mean sedimentation rates shift from 45 cm kyr−1 between 0 and 110 m to 30 cm kyr−1 from 110 to 240 m b.l.f. Tuning of minima and maxima of gamma ray and potassium values versus LR04 extrema, in combination with eight independent tephrostratigraphical tie points, allows establishing of a robust age model for the downhole logging data over the past 630 kyr.
Highlights
Lake Ohrid is located at the border between the former Yugoslav Republic of Macedonia (FYROM) and Albania (40◦70 N, 20◦42 E) in the central Mediterranean region (Fig. 1a)
The output curves from spectral gamma ray (SGR) were compared to estimate the contribution of the spectral components to the total gamma ray
After the anchor points from tephra deposits were defined, significant variations in the data were correlated; a very similar cyclicity with a positive correlation between Gamma ray (GR) and K from downhole logging data and δ18O data was observed (Fig. 2a)
Summary
Lake Ohrid is located at the border between the former Yugoslav Republic of Macedonia (FYROM) and Albania (40◦70 N, 20◦42 E) in the central Mediterranean region (Fig. 1a). It is considered as one of the oldest, continuously existing lakes worldwide. Several pre-site studies between 2004 and 2012, such as multichannel seismic and shallow coring, demonstrated the potential of Lake Ohrid to yield a complete and continuous palaeoclimatic record At the main drill site, the “DEEP site” in the central deep basin of Lake Ohrid (Fig. 1b), multiple coring and downhole logging tools were applied
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
