Comparing extension on multiple time and depth scales in the Corinth Rift, Central Greece
Résumé
The young (< 5 Ma) Corinth Rift is an ideal natural laboratory to investigate rift deformation mechanisms by comparing extension rates determined by various methods spanning different depth and time ranges. Corinth Rift geodetic extension rates averaged over 5–100 yr have been interpreted to increase from ∼5 mm yr –1 or less in the east to >10–15 mm yr –1 in the west. We quantify total upper-crust and whole-crust extension on three profiles across the Corinth Rift. Whole-crust extension is greater across the central rift (∼11–21 km) than across the western part of the rift (∼5–13 km). This correlates with the overall rift morphology, which shows maximum basement subsidence, sediment accumulation, rift width and greatest summed Late Quaternary fault displacements in the central basin, but contrasts with the pattern of geodetic extension rates which are greater to the west of the central basin. The E–W increase in strain rates interpreted from geodetic data cannot have persisted over rift history to produce the observed rift morphology. We suggest the discrepancy between short-term and long-term extension patterns is related to shifts in the loci of maximum extension due to fault growth and linkage during Corinth Rift history, and is likely a characteristic of rift development in general. Total upper-crust and whole-crust extension estimates in the western rift, where extension estimates are best constrained, are within error. We propose that uniform pure-shear extension is a viable extension mechanism in the western rift and crustal extension estimates do not require the existence of a major active N–S dipping detachment fault.
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