And now for some geology from Rob Gawthorpe – one of the scientists sailing on Expedition 381.
The location of the first IODP Expedition 381 borehole in the Gulf of Corinth gives a different view of the onshore Corinth Rift geology. In the early morning light the view from the Fugro Synergy gives an excellent overview of the southern shores of the Gulf of Corinth and the northern Peloponnesus around the town of Xylokastro.
To the east of Xylokastro, marine terraces are clearly seen as sub-parallel ‘steps’ in the landscape rising southward, recording older shorelines formed during previous sea-level highstand, now uplifted in the footwall of active faults under the gulf. (Editor note: see diagram for an explanation of footwalls and hangingwalls). The terraces extend back in time to at least 0.6 Ma (million years) and unconformably (not successive in age) overlie older deep-water syn-rift sediments that record the early phase of evolution of the Corinth Rift when the rift was mainly located onshore.
Image courtesy of http://www.thinglink.com
The Sythas River flows along the major valley south of Xylokastro. The high topography at the head of this valley is in pre-rift rocks that are in the footwall of the now inactive southern border fault of the Corinth Rift. In this part of the rift it is called the Killini-Trikala-Kefalari Fault.
West (right) of Xylokastro, the prominent N-facing hillside near the coast that is in shadow is the West Xylokastro Fault. This fault is thought to have been active between ca. 1.8 to 0.8 Ma (million years). Behind (S) of this fault, the mountain Mavro Oros, is composed of older fluvial (river) and deltaic deposits that fed Late Pliocene/earliest Pleistocene turbidites (sediment flows driven by gravity) exposed along the Sythas valley.
On the right of the photo, light coloured cliffs are deltaic and turbidite deposits interpreted to be synchronous (occurring at the same time) with activity on the West Xylokastro Fault, but now uplifted in the footwall of the active faults under the Gulf. The higher cliff is the Evrostini delta that prograded into >600 m of water (indicated by the height of its’ foresets – the inclined part of a delta formed as sediments are laid down along the delta front). The lower cliffs, near the coast, are deep-water turbidite deposits sourced from the Evrostini delta. Both delta and turbidites are now uplifted in the footwall of active faults under the gulf, with the fluvial topsets of the Evrostini delta now elevated to ca. 1000 m above sea-level.
In addition to IODP drilling in the Gulf of Corinth, a complementary project (Syn-Rift Systems project) led by the University of Bergen has just started drilling the onshore sediments near the town of Xylokastro, targeting the older syn-rift sediments.
More information about the onshore geology around Xylokastro can be found at:
Main panoramic image courtesy of RGawthorpe@ECORD_IODP