Urban geoarchaeology and environmental history at the Lost City of the Pyramids, Giza: synthesis and review

Abstract Sediment accretion in ancient urban sites and tells records a combination of cultural and geomorphic processes. Urban geoarchaeology is focused on site accumulation, collapse, weathering and erosion, as constrained by architectural plans and structures. These may document settlement growth and decay, as well as environmental history, posing a multidisciplinary challenge of interactive and fluctuating processes. Part of a World Heritage site , the Lost City of the Pyramids (Heit el-Ghurab), at the desert and floodplain margins of Giza, was centered on a Workmen's Town that channeled the roles of seasonal workmen, artisans, and administrators during construction of the Menkaure Pyramid and preparation of the funerary cult for that pharaoh (∼2532–2503 BCE). Built across a normally dry wadi course, the site was badly chosen and vulnerable to a coeval high-amplitude precipitation anomaly of perhaps 120 yr, during which mudbrick meltdown, catastrophic flash floods, and mass-movements destroyed the royal complex of mudbrick galleries, workshops and bread-making kilns once every 4 years or so. In addition, thick alluvial fans advanced 1 km or more across the Nile floodplain, before dissection was initiated by downcutting channels. Despite this dynamic environmental history, the site was repeatedly rebuilt and ruined, with structural and human consequences. This Old Kingdom (Dynasty 4) paleoclimatic anomaly did not however support a significant improvement of Saharan ecology, and summer monsoonal rains never extended this far north (30°N). Such a destructive period of extreme precipitation is novel for the Holocene record of the NE Sahara, and requires a synoptic explanation in the mid-latitude jet stream, rather than the tropical monsoonal circulation, to contradict current theoretical expectations. This anomaly was repeated on a subdued scale during the Early Middle Ages. Nile floods did not impinge upon the site during Old Kingdom times, but were demonstrably higher ∼700 BCE, and again during Early Roman or Coptic times. Residual subdisciplinary problems are identified and explicitly discussed in terms of the strategies and structure of multidisciplinary investigation.