Editing Richat Structure (section)

== Archaeology ==
[[Image:Richat Structure - SRTM.jpg|thumb|right|250px|A topographic reconstruction (scaled 6:1 on the vertical axis) from satellite photos. False colouring as follows: <br />• Brown: bedrock <br />• Yellow/white: sand <br />• Green: vegetation <br />• Blue: salty sediments]]
The Richat Structure is the location of exceptional accumulations of [[Acheulean]] [[Artifact (archaeology)|artifact]]s.<ref name="Monod1975a" /><ref name="SaoOthers2008a" /> These Acheulean archaeological sites are located along [[wadi]]s that occupy the outermost annular depression of this structure. Pre-Acheulean stone tools also have been found in the same areas. These sites are associated with rubbly [[outcrop]]s of [[quartzite]] that provided the raw material needed for the manufacture of these artifacts. The most important Acheulean sites and their associated outcrops are found along the northwest of the outer ring, from which Wadi Akerdil heads east and Wadi Bamouere to the west. Sparse and widely scattered [[Neolithic]] spear points and other artifacts have also been found. However, since these sites were first discovered by Théodore Monod in 1974,<ref name="Monod1975a">{{Cite journal |last=Monod |first=T. |year=1975 |title=Three Pebble Deposits in the Mauritanian Adrar (Western Sahara) |journal=Provence Historique |volume=99 |pages=87–97}}</ref> mapping of artifacts within the area of the structure have found them to be generally absent in its innermost depressions. So far, neither recognizable midden deposits nor manmade structures have been recognized and reported from the structure. This is interpreted as indicating that the area of the Richat Structure was used for only short-term hunting and stone tool manufacturing. The local apparent wealth of surface artifacts is the result of the concentration and mixing by deflation over multiple [[glacial]]-[[interglacial]] cycles.<ref name="SaoOthers2008a">{{Cite journal |last1=Sao |first1=Ousmane |last2=Giresse |first2=Pierre |last3=de Lumley |first3=Henry |last4=Faure |first4=Olivier |last5=Perrenoud |first5=Christian |last6=Saos |first6=Thibaud |last7=Rachid |first7=Mouamar Ould |last8=Touré |first8=Ousmane Cherif |year=2008 |title=The Sedimentary Environments of the Pre-Eulean and Aeulean Deposits of the Akerdil and Bamouéré Wadis (Guelb er-Richât, Adrar, Mauritania), A First Approach |journal=L'Anthropologie |volume=112 |issue=1 |pages=1–14 |doi=10.1016/j.anthro.2008.01.001}}</ref><ref name="GiresseOthers2012a" />

Artifacts are found, typically redeposited, deflated, or both, in [[Late Pleistocene]] to early [[Holocene]] gravelly [[mud]], muddy [[gravel]], [[clay]]ey [[sand]], and [[silt]]y sand. These [[sediment]]s are often cemented into either [[concretion]]ary masses or beds by [[calcrete]]. Ridges typically consist of deeply weathered [[bedrock]] representing truncated [[Cenozoic]] [[paleosol]]s that formed under tropical environments. The Pleistocene to Middle Holocene sediments occur along wadis as the thin, meter- to less-than-meter-thick accumulations in the interior annular depressions to {{convert|3 to 4|m|ft|}}-thick accumulations along the wadis in the outermost annular depression of the structure. The gravelly deposits consist of a mixture of slope scree, [[debris flow]], and [[fluvial|fluviatile]] or even torrential flow deposits. The finer-grained, sandy deposits consist of [[Aeolian dust|eolian]] and [[playa lake]] deposits. The latter contain well-preserved [[freshwater]] [[fossil]]s. Numerous concordant [[radiocarbon]] dates indicate that the bulk of these sediments accumulated between 15,000 and 8,000 [[Before Present|BP]] during the [[African humid period]]. These deposits lie directly upon deeply eroded and weathered bedrock.<ref name="GiresseOthers2012a">{{Cite journal |last1=Giresse |first1=Pierre |last2=Sao |first2=Ousmane |last3=de Lumley |first3=Henry |year=2012 |title=Paleo-environmental Study of the Quaternary Sediments of Guelb and Richât (Adrar of Mauritania) with Respect to Neighboring or Associated Sites of the Lower Paleolithic. Discussion and Perspectives |journal=L'Anthropologie |volume=116 |issue=1 |pages=12–38 |doi=10.1016/j.anthro.2011.12.001}}</ref>