Magnetostratigraphic study of the Melka Kunture archaeological site (Ethiopia) and its chronological implications

A magnetostratigraphy is established for the Melka Kunture archaeological site of Ethiopia, whose chronological setting needed improvement. The magnetostratigraphy is constructed from four distinct stratigraphic sections, Garba-IV (5 sites), Gombore-I (21 sites), Gombore-II (8 sites), and Simbiro (13 sites). Natural remanent magnetizations (NRM) were measured and analyzed over a total of 214 specimens to isolate the characteristic components of magnetization and determine magnetic polarities. Two magnetization components were isolated in every sample analyzed: (i) a low-temperature (low coercivity) secondary normal component and (ii) a high-temperature characteristic component of normal or reversed polarity and allows to identify five magnetozones (N1–R1–N2–R2–N3). Rock magnetic analysis attests that the magnetization is carried by magnetite or titanomagnetite within the range of pseudo-single domain grain sizes. Anisotropy of magnetic susceptibility (AMS) supports a sedimentary origin of the magnetic remanence. Based on recent 40Ar/39Ar geochronological dating of the site, faunal constraints and a magnetostratigraphic pattern, the sequence is correlated to the time between the early Matuyama chron (<1.80 Ma) and early Brunhes chron (∼0.709 Ma) of the geomagnetic polarity time scale (GPTS). Completing recent 40Ar/39Ar age series, the magnetostratigraphy study presented here allows computation of interpolated ages for various faunal and artifact findings at Melka Kunture and similar fossiliferous deposits in the region.