Fluvial deposition and erosion through time was largely controlled by the base level of downstream depocenters as the northward-flowing axial Awash River was tectonically dropped and/or volcanically dammed by the ongoing extension-related tectono-volcanic activity of the Afar Rift. Understanding the complex and dynamic erosional/depositional interfaces that operated here during the Pleistocene was key to the Halibee chronological framework presented below. These results demonstrate how chronological control can be obtained in tectonically active and stratigraphically complex settings to precisely calibrate crucial evidence of technological, environmental, and evolutionary changes during the African Middle and Late Pleistocene. Additional 40Ar/ 39 results on an underlying tuff refine its age to 158.1 ± 11.0 ka, providing a more precise minimum age for MSA lithic artifacts, fauna, and H. Associated fauna, flora, and Homo sapiens fossils are thereby now fixed between 106 ± 20 ka and 96.4 ± 1.6 ka (all errors 2σ). Paired 14C and 230Th/U burial ages of OES agree at ∼31 ka for an older LSA locality, validating the newer method, and in turn supporting its application to stratigraphically underlying MSA occurrences previously constrained only by a maximum 40Ar/ 39Ar age. We apply the recently developed 230Th/U burial dating of OES to bridge the temporal gap between radiocarbon ( 14C) and 40Ar/ 39Ar ages for the MSA and provide 14C ages to constrain the younger LSA archaeology and fauna to ∼24 to 21.4 ka. We introduce these artifacts and fossils, and determine their chronostratigraphic placement via a combination of established radioisotopic methods and a recently developed dating method applied to ostrich eggshell (OES).
Professional assistance and detailed engineering analysis may be required to address any of the above considerations.įlood levels indicated on the maps are the minimum recommended elevations for floodproofing requirements.The Halibee member of the Upper Dawaitoli Formation of Ethiopia’s Middle Awash study area features a wealth of Middle and Later Stone Age (MSA and LSA) paleoanthropological resources in a succession of Pleistocene sediments. Minimum floodproofing requirements can then be incorporated into building bylaws, subdivision approvals, and local government planning and regulations.
A 200-year flood can occur at any time in any given year, exceed the indicated flood level, and portions of the floodplain can flood more frequently.įloodplain maps show minimum elevations for floodproofing. Learn about emergency planning floodplain mapsĪ floodplain map delineates the area that can be expected to flood, on average, once every 200 years.
Flooding may still occur outside of these floodplain areas.Ĭoastal floodplain mapping identifies coastal flood hazards, such as sea level rise, and provides guidance for land use planning.įloodplain maps of the extent of the Fraser River floodplain are available for the purposes of flood emergency planning. that are highly susceptible to flooding are as follows. Floodplain maps show the location of the normal channel of a water course, surrounding features or developments, ground elevation contours, flood levels and floodplain limits-the elevation and horizontal extent of the high water marks of a 200-year flood.