## 2 Notes on the Theory, Method and Data
### Data: Remote Sensing and Terrestrial
#### 2.4.4 Archaeological Data  
River valleys, lakes and/or inner seas played a vital role in human prehistory [23]. In the Western Desert of Egypt, which is the focus of this study, permanent settlement has been confined since the Late Holocene (after 4200 BP (BP, before present, calibrated years)) to five major oases in the northern and central parts of the currently hyper-arid desert (Figure 5). Nevertheless, varied archaeological evidence attests to repeated periods of greater humidity when this region, just as the entire Sahara, was periodically habitable and regularly occupied by diverse human groups (e.g., [24; 25]). The available archaeological data can be used to test the hypothesis of the existence of paleolake and paleoriver systems detected using the gravity signals. Figure 4: Gas fields in Northern Egypt, mostly offshore, redrawn according to [20; 22]. Figure 5: Where we are in Egypt: topography from _ETOPO 1_ together with the names of important places to introduce the area of our study: [PERSON], ABS Abu Ballas Scarp-land, [PERSON] (Limestone) Plateau, [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON]. Red rectangle: the area of Kharga-Toshka (TK), evaluated in this study (Section 4.3). Black dots: areas with archaeological evidence falling within the maximum expansion of the Holocene occupation based on [24] (their figure 3c). [PERSON] and [PERSON] [24] gathered data from 150 excavations at Holocene sites in support of their hypothesis of the climate-controlled occupation of the Eastern Sahara (Figure 6). The locations of archaeological sites from their phase of maximum expansion of human occupation (~9000-7300 BP; [24] (their figure 3c)) were used in [4] to locate possible paleolakes in the northern part of the Western Desert of Egypt (Figure 7). In this study, we limit the spatial focus to the south-eastern part of the Egyptian Western Desert but work with more detailed archaeological data covering both Holocene and Pleistocene occupation. Our research area consists of two depressions. The southern part contains the lowland between the Kiseiba Scarp in the west (ca. 250 km west of the Nile), Eocene Limestone Plateau in the north and Wadi  
Figure 6: Climate-controlled occupation in the Eastern Sahara during the main phases of the Holocene after [24] (their figure 3a–d). With the abrupt arrival of monsoon rains ~10,500 BP, the hyper-arid desert to the west of the Nile was replaced by savanna-like environments, while the Nile Valley was too moist for occupation. After ~7300 BP, desiccation of the Egyptian Sahara began again. Redrawn following the data from [24]. Figure 7: The archaeological localities (black dots) over the map with the gravity disturbances \(\Delta\)g (mGal) from EIGEN 6C4: the positions of archaeological sites of the Holocene occupations between ~10,500 and ~7300 BP in the Eastern Sahara, Western Desert of Egypt, were utilized (after [24]). Toshka in the east (ca. 70 km west of the Nile). The current shape of this area is the result of intensive and repeated erosion, deflation and deposition during the Pleistocene and Holocene [26; 27]. The average elevation of this area is around 240 m asl, with the desert surface gradually rising towards the south. The surface of the lowland is dotted with numerous low-lying, internally drained and enclosed basins with elevation well below 200 m asl [27]. The depression features evidence of occupation during the Lower Paleolithic (\(\sim\)500,000-300,000 BP) and Middle Paleolithic (\(\sim\)175,000-70,000 BP). Nevertheless, in consequence of major reworking of the area during the hyper-arid phase between \(\sim\)70,000 BP and the beginning of the Holocene (\(\sim\)11,500 BP), the Pleistocene evidence is only rarely found in situ in elevated locations [28]. The Holocene remains are mostly tied to the low-lying basins or playas and usually attest to multiple reoccupations of the same locations (in particular, see [27; 28; 29]).