Meteorite terrestrial ages in Oman based on gamma spectrometry and sediment dating, focusing on the Ramlat Fasad dense collection area

Abstract

We combine the search for young meteorites in the Omani‐Swiss collection (˜1140 fall events collected 2001–2018) using 22Na and 44Ti with luminescence and 14C sediment ages from the Ramlat Fasad (RaF) dense collection area (DCA) of Oman to obtain combined terrestrial ages and maximum accumulation times, and test whether the proportion of young meteorites is consistent with the models of meteorite flux and weathering. Gamma‐ray spectrometry data for 22Na show that two (0.17%) of the meteorites in the collection fell during the 20 yr preceding this study, consistent with the rates of meteorite accumulation. In the RaF DCA, meteorites are found on Quaternary to Neogene sediments, providing constraints for their maximum terrestrial ages. 44Ti activities of the RaF 032 L6 strewn field found on deflated parts of active dunes indicate an age of 0.2–0.3 ka while dune sand optically stimulated luminescence ages constrain an upper age of 1.6 ka. Extensive sediment dating using luminescence methods in the RaF DCA area showed that all other meteorite finds were made on significantly older sediments (>10 ka). Dense accumulations of meteorites in RaF are found on blowouts of the Pliocene Marsawdad formation. Our combined results show that the proportion of meteorites with low terrestrial ages is low compared to other find areas, consistent with the previously determined high average terrestrial age Oman meteorites and significantly older than suggested by models of exponential decay. Oman meteorites may commonly have been buried within dunes and soils over extended periods, acting as a temporary protection against erosion.

Terrestrial ages of seven meteorite strewn fields and two single unpaired meteorites from the Sultanate of Oman determined using 14C and 10Be

“…In recent fieldwork, strongly deflated small areas close to large star dunes, the so‐called blowouts, were also a major target of the search campaigns. The find density in these areas is approximately 30 meteorites per km 2 , that is, well above the previously determined average density of 1–2 finds per km 2 typical for Oman (data used from 2001 to 2014 search period; OSMS database; Hofmann et al., 2014, 2018; Rosén et al., 2021).…”

“…Histogram of the best estimate (see text) terrestrial ages for the studied strewn fields and for the previously dated strewn fields Ghubara (Jull et al., 2013) and Ramlat Fasad 032 (Rosén et al., 2021). The dashed line indicates the terrestrial age distribution of individual meteorites ( n = 128) previously determined by Zurfluh et al.…”

“…(2018), and Rosén et al. (2021). The climate of south central Oman is arid with an annual precipitation of <25 to 50 mm (Edgell, 2006), the mean annual temperature in Hayma (19°57.5′N 56°16.5′E) is 28.6 °C (http://average-weather.com).…”

“…A system of alluvial fans forms a transitional belt to the Oman Mountains in the north and to the Dhofar Mountains in the south. Detailed descriptions of the geological features relevant for meteorite accumulations are given by Al-Kathiri et al (2005), Fookes and Lee (2009), and Rosén et al (2021. The climate of south central Oman is arid with an annual precipitation of <25 to 50 mm (Edgell, 2006), the mean annual temperature in Hayma (19°57.5 0 N 56°16.5 0 E) is 28.6 °C (average-weather.com).…”

“…Plot of the relation between the mean weathering grade (scale of Zurfluh et al, 2016) and our best-estimate terrestrial ages (squares). Circles are the mean ages for different weathering degrees from Zurfluh et al (2016).Diamonds represent the young strewn fields Ramlat Fasad 032(Rosén et al, 2021; see text) and Ghubara(Jull et al, 2013). Note that weathering grades are plotted as individual numerical classes.…”