Magnetostratigraphy of Pleistocene Sediments from the Republic of Georgia - Dating and Correlation of Climate Signals

• Applicant: Professor Dr. Valerian Bachtadse
• Subject Area: Geophysics ; Palaeontology
• Term: from 2013 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 245125135

• Final Report Year: 2017

Final Report Abstract

The precise Eurasian chronostratigraphy of the Neogene-Quaternary period is still hampered by the existence of numerous regional stages often lacking independent and absolute age constraints. Therefore, detailed paleoclimatic reconstructions of areas like the Caucasus are still poorly constrained and the influence of climate variability on faunal interchange between Africa and Eurasia in the late Neogene-Quaternary is still difficult to address. During the last decades, Quaternary sections from western Georgia have produced a wealth of paleoclimatic proxy data. Unfortunately, these sections do not have a robust age control. This is especially true for the Gurian stage which has been vaguely defined as being coeval with the lower Pleistocene on the basis of poorly documented bio- and magnetostratigraphic data. In order to constrain the age of the Gurian stage, a detailed magnetostratigraphic study has been carried out. All major sections with known Gurian sediments in the former Rioni bay (a marine restricted area to the southeast of the Major Caucasus) have been studied. Our results confirm for the first time the strict correlation between the Gurian succession and the Calabrian stage (1.80 − 0.781M a).In addition, our data provides further information on the tectonic setting of the Rioni bay during the Calabrian in this region: (1) in the north, Gurian sediments were unconformably deposited on older Meotian sediments in a piggy back basin, (2) in the south, Gurian sediments are conformably overlying Kujalnician (Plio-Pleistocene) strata, (3) magnetostratigraphic correlation among sections indicate drastic changes in sediment accumulation rates within the basin, (4) rock magnetic experiments reveal significant magnetomineralogical differences between Gurian and the underlying Miocene sediments likely documenting a transition related to changes in oxic conditions, supply of terrigenous material and sedimentation rate close to the Miocene-Pliocene boundary. These results provide a robust basis for further tectonic and paleoclimatic investigations of this region.

Publications

• (2013). New Magnetostratigraphic Correlation of Major Outcrops of the Guria Sequence, Western Georgia, ROCEEH -VW workshop The role of the Southern Caucasus on early human evolution and expansion refuge, hub or source area?, Tbilisi, Georgia, 1520 October 2013
  Kirscher, U., Oms, O., Bruch, A.A., and Bachtadse,V.
  
• (2017). Correlating the Calabrian in the Western Transcaucasus basin (Georgia): magnetostratigraphic dating of the Gurian stage, Quaternary Science Reviews
  Kirscher, U., Oms, O., Bruch, A.A., Shatilova, I., Chochisvili, G., Bachtadse, V.
  
• The importance of the Gurian stage: magnetostratigraphic correlation of the Calabrian in the southern Caucasus and its paleoclimatic implications, Session CL5.03/GM2.3 Advances in Quaternary Geochronology (EGU, Vienna, 2017)
  Kirscher, U., Oms, O, Bruch, A.A., Shatilova, I., Chochishvili, G., and Bachtadse, V.