Temporally constant Quaternary uplift rates and their relationship with extensional upper-plate faults in south Crete (Greece), constrained with 36Cl exposure dating.

Abstract

Preserved sets of marine terraces and palaeoshorelines above subduction zones provide an opportunity to explore the long-term deformation that occurs as a result of upper-plate extension. We investigate uplifted palaeoshorelines along the South Central Crete Fault and over its western tip, located above the Hellenic Subduction Zone, in order toderive uplift rates and examine the role that known extensional faults contribute to observed coastal uplift. We have mapped palaeoshorelines and successfully dated four Late-Quaternary wave-cut platforms using in-situ 36Cl exposure dating. These absolute ages are used to guidea correlation of palaeoshorelines with Quaternary sea-level highstands from 76.5 to ~900 ka; the results of which suggest that uplift rates vary along fault strikes but have been constant for up to 600 ka in places. Correlation of palaeoshorelines across the SCCF results in a throw-rate of 0.41 mm/yr and, assuming repetition of 1.1 m slip events, a fault-specific earthquake recurrence interval of approximately 2700 years. Elastic-half space modellingimplies that coastal uplift is related to offshore upper-plate extensional faults. These faults may be responsible for perturbing the uplift rate signals in the south central Crete area. Our findings suggest that where uplifted marine terraces are used to make inferences about the mechanisms responsible for uplift throughout the Hellenic Subduction Zone, and other subduction zones worldwide, the impact of upper-plate extensional faults over multipleseismic cycles should also be considered.

Distributed normal faulting in the tip zone of the South Alkyonides Fault System, Gulf of Corinth, constrained using 36Cl exposure dating of Late-Quaternary wave-cut platforms.

“…The ages of four notches observed on Cape Heraion were dated to between 190-440 A.D. and 4440-4320 A.D. and used to infer coseismic footwall uplift increments of 0.8 m from earthquakes with recurrence intervals of ~1600 years (Pirazzoli et al, 1994). However, 0.8m has been suggested to be a relatively high value for coseismic footwall uplift (Cooper et al, 2007;Boulton and Stewart, 2015;Schneiderwind et al,2017b;Meschis et al, 2019). Whatever their mode of formation, we show below that the notches are deformed by active faulting and use this as part of our explanation of the geological history of Cape Heraion.…”

“…Exploring the deformation of marine terraces and wave-cut platforms relies on obtaining age controls for terraces, accurate geomorphic mapping of terrace features and knowledge of the timing and relative elevations of sea-level highstands (Robertson et al, 2019). Existing coral ages on Cape Heraion at localities C and F ( Figure 4a) dated using (Roberts et al, 2009) and a platform at m (Collier et al, 1992;Vita-Finzi et al, 1993;Leeder et al, 2003;Leeder et al, 2005;Dia et al, 2007;Houghton, 2010).…”

“…Other pathways of 36 Cl production that must be considered are from low-energy neutrons (Schimmelpfennig et al, 2009) and negative muons, which are the dominant production mechanism for 36 Cl at greater depths (Dunai, 2010). We use the approach outlined in Robertson et al (2019) to identify surfaces that have experienced minimal erosion based on the presence of preserved lithophagid borings and millholes. The depth of lithophagid borings upon formation is between 3-9 cm (Peharda et al, 2015) while millholes, that is, erosional hollows formed by pebble agitation in the intertidal zone, are usually a few centimeters to a few decimetres deep.…”

“…The preservation of lithophagid borings and millholes on bioclastic packstone and limestone surfaces ( Figure 6) indicate total erosion values of much less than 0.2-0.3 m, whilst samples from the tops of bioherms are expected to have experienced total erosional values similar with the removed depth of bioclastic packstone eroded from the surface of ~0.6 m. These limestone/packstone and bioherm values equate to erosion rates of 0.1 and ~6.0 mm/ky respectively. The 0.1 mm/yr value is the same as that used on limestone wave-cut platforms dated using 36 Cl exposure dating in south Crete (Robertson et al, 2019).…”

“…Investigations using deformed Quaternary marine terraces and their associated wave-cut platforms (e.g. Armijo et al, 1996;Roberts et al, 2009, Roberts et al, 2013Binnie et al, 2016;Jara-Munoz et al, 2017;Meschis et al, 2018;Robertson et al, 2019) allow deformation rates to be measured over 10 4-5 years, and therefore displacement associated with the very low slip rates of individual tip-zone faults can be resolved.…”