A SEQUENCE-STRATIGRAPHIC FRAMEWORK FOR THE ZEBRA NAPPE, SOUTHERN NAUKLUFT MOUNTAINS, NAMIBIA
Building on a revised geologic map and tectonic framework for the southern Naukluft Mountains, we present a new facies model and stratigraphic framework for the Zebra Nappe. The ~600 m of carbonate and clastic sediments in the Zebra Nappe are divided into units along the lines of Hartnady (1978), and here we define three depositional sequences. The lower sequence, containing peritidal, upper-shoreface, and shallow subtidal facies, records a shallow-water environment across the study area. The second sequence is a deepening facies system that consists of west-thickening shale wedges interspersed with compressed regressive intervals of shallower facies belts, culminating in reworking surfaces. The final sequence is a grainy limestone shoal varying between ribbon and intraclast limestone, and cross-stratified grainstone.
The Zebra Nappe does not contain facies indicative of “cap-carbonate” strata, and δ13C and δ18O chemostratigraphy does not capture known terminal Proterozoic isotope excursions (e.g. the Shuram excursion), but consistent values of -2 near the top of the section potentially match early Ediacaran deposition. Detrital zircons within several key sandstone packages are sourced entirely from the Kalahari Craton. The lack of sediment input from the Damara orogenic belt contrasts strongly with the allochthonous Nama group. Thus, the Zebra Nappe is not correlated with any known stratigraphic package exposed in southern Namibia; it likely represents a preserved fragment of a missing pre-Damara passive margin of the Kalahari craton.