Drilling the Corinth active rift, Greece: High resolution records of interacting tectonics, climate and sedimentation during rift evolution

Abstract:

The Corinth Rift, Central Greece, is one of the most rapidly extending regions on Earth with accompanying high seismicity levels. Rifting at this location began about 5 Ma and the rift is now at sea level with a well preserved syn-rift sedimentary record. This young rift also experiences significant environmental changes as a sea-level controlled, temporarily isolated basin. Subsidence and sedimentation rates are high, thus the record has very high temporal resolution. IODP Expedition 381 drilled the deposits of the most recent phases of rifting, representing the last ~1-2 Ma, in 2017, with objectives focused on early rift-fault evolutionary history and surface processes and sediment cycling. This was the first IODP drilling of a rift so young and has generated the first long high-resolution record of early rifting. The new cores and logs confirm that the basin fluctuates between marine and lake/isolated conditions driven by eustatic sea level. Importantly, the boreholes provide the first detailed geochronological constraints for the offshore stratigraphy. The most recent phase of rifting began ~0.8 Ma ago and evidence of Pliocene rifting found at the base of one hole. Sedimentation rates vary with climatic and rift flank vegetation controls, with increased sediment flux in glacial periods (up to 3-4 mm/yr). Climate, sea level and basin environment/hydrodynamics also impact frequency, scale and type of sediment gravity flows and deposits. The potential for a high resolution climate and sea level record is also good due to the very high sedimentation rates within the basin. The new chronostratigraphy and time-depth conversion is being used to quantify fault slip rates through time and larger scale rift evolution by correlation to the dense seismic reflection network. Active fault slip rates along rift are up to 5-6 mm/yr. The results provide evidence for increases in extension rates, and change in rift geometry through time, often at 100 kyr timescales, and spatial variations in degree of strain localisation along the rift.