Rates of uplift investigated through 230Th dating in the Gulf of Corinth (Greece)

The Sr, U and Th isotope compositions of fourteen coral samples from raised terraces on the south side of the Gulf of Corinth, Greece, have been analysed by high-precision mass spectrometry. 234U–230Th ages of pure coral aragonite together with 87Sr/86Sr determinations provide the basis for an investigation of tectonic uplift rates in the W. Aegean over the last 350 ka. The Corinth basin is a continental fault-bounded depression formed by crustal extension northeast of subduction along the Hellenic trench and in the vicinity of the Aegean volcanic arc. isotope composition of present-day seawater in the Gulf of Corinth is indistinguishable from that in the North Atlantic, but this was not the case during earlier high stands (120, 190 and 240 ka ago) when 87Sr/86Sr ratios, as estimated from the corals, were apparently significantly lower than the ratios of their open-ocean counterparts. Although the cause of the earlier discrepancy between the two reservoirs is unknown, it is likely to result from one of two processes. Either circulation between the Gulf of Corinth and the open ocean may have been restricted at certain earlier highstands, or the lower Sr isotope compositions could be the result of diagenetic effects. The latter hypothesis is favoured by large variations in the initial 234U/238U ratio of the corals, by their unusually high Th contents, and by the observation that the underlying massive Miocene carbonate is severely altered. es of the corals as determined by mass spectrometry ranges between 70.2 and 385.5 ka for samples from terraces at elevations of 7 to 65 m above present sea-level. A mean uplift rate for this area of 0.3 mm/yr over the last 350 ka has been estimated by combining the coral ages with terrace heights, allowing for changes in sea-level during this period. The uplift here is probably caused by footwall uplift adjacent to large normal faults, and put constraints on likely fault slip rates, extension rates, and the timescales of earthquake recurrence.