The Oligocene–Miocene transition climate recorded in a lacustrine sequence, Ebro Basin: preliminary insights

Abstract

The climate evolution across the Oligocene–Miocene transition has been studied through a 23.5 to 22 Ma succession in the eastern Ebro Basin, dated by magnetostratigraphy. The study is based on the δ13C and δ18O composition coupled with sedimentological analysis of a dominantly lacustrine and palustrine carbonate succession, focusing on the limestone facies. The deposits formed in alluvial plain, saline mud flat, and carbonate lacustrine and palustrine depositional environments. Changes in lake water level and hydrodynamics, and biological processes triggered the formation of distinct carbonate facies, causing isotopic differences among them. The isotopic variations likely reflect changes in the precipitation/evaporation ratio and temperature in the Ebro Basin that might be the regional record of the Mi-1 Glaciation. A change in variability in δ13C and δ18O and an inflection in δ13C mark the Oligocene–Miocene boundary (23.03 Ma). The decrease in δ13C and δ18O variability may correspond to steadier depositional, climatic and hydrological conditions through time.

Keywords

• Oligocene–Miocene transition
• lacustrine and palustrine carbonates
• paleoclimate
• δ13C and δ18O
• NE Iberia