Slip-rate on the Main Kopetdag (Kopeh Dagh) Strike-slip fault, Turkmenistan, and the active tectonics of the South Caspian

Description of Data:

Samples for IRSL and U-series dating to determine slip-rate were collected in the fan surfaces at four sites in the Main Kopetdag fault (MKDF) in Turkmenistan, visited in November 2016. One sample for IRSL dating was taken from each of pits 1 (38.67743N 56.69678E – sample T16-01, taken from the base of a silt layer overlying gravel deposits) and pit 3 (38.67356N 56.71909E – sample T16-07, taken from a mixed sand/ fine gravel layer within the alluvial sequence). Two samples were taken from pit 4 (38.67529N 56.72086E – samples T16-05 and T16-06, both extracted from a sandy silt layer within the alluvial gravel sequence). Hard, cemented, limestone cobbles under a thin (30 cm) soil were encountered in pit 2 (38.68587N 56.67277E), which were not suitable for sampling for luminescence dating. Instead, three examples of the pedogenic carbonate cements on the underside of limestone cobbles were collected, from which individual carbonate layers were drilled and dated using the U-series method as described in the associated manuscript (Walker et al., 2021). These samples yielded ages that were widely variable between the three pebbles, and between sub-samples from the same pebble, and are not considered to be useful. See associated manuscript (Walker et al., 2021) for details of IRSL dating procedures and age calculation. Data were collected on a Risø TL-DA-20CD DASH automated reader, and anaysed in the software package Analyst v4.57. Parameters used in the age estimation are contained in the data table in readmeIRSL_with-altitudes.doc. All four IRSL samples are considered to be contemporaneous based upon the geomorphic setting, and all showed grouping equivalent to ~100 ka in age. The four individual IRSL samples yielding ages of 104 ± 8 ka (T16-01), 107 ± 8 ka (T16-05), 91 ± 9 ka (T16-06), and 117 ± 10 ka (T16-07) were combined using a central age to provide an age estimate of 105,200 ± 4,700 years. Given a displacement of 949 ± 94 m of the fan surface, this age range yields a slip-rate of 7.8-10.4 mm/yr (or 9.1 ± 1.3 mm/yr).