Holocene Aridity-Induced Interruptions of Human Activity along a Fluvial Channel in Egypt’s Northern Delta

Abstract

Geoarchaeological information presented here pertains to a subsidiary Nile channel that once flowed west of the main Sebennitic distributary and discharged its water and sediments at Egypt’s then north-central deltaic coast. Periodical paleoclimatic episodes during the later Middle and Upper Holocene included decreased rainfall and increased aridity that reduced the Nile’s flow levels and thus likely disrupted nautical transport and anthropogenic activity along this channel. Such changes in this deltaic sector, positioned adjacent to the Levantine Basin in the Eastern Mediterranean, can be attributed to climatic shifts triggered as far as the North Atlantic to the west, and African highland source areas of the Egyptian Nile to the south. Of special interest in a study core recovered along the channel are several sediment sequences without anthropogenic material that are interbedded between strata comprising numerous potsherds. The former are interpreted here as markers of increased regional aridity and reduced Nile flow which could have periodically disrupted the regional distribution of goods and nautical activities. Such times occurred ~5000 years B.P., ~4200–4000 years B.P., ~3200–2800 years B.P., ~2300–2200 years B.P., and more recently. Periods comparable to these are also identified by altered proportions of pollen, isotopic and compositional components in different radiocarbon-dated Holocene cores recovered elsewhere in the Nile delta, the Levantine region to the east and north of Egypt, and in the Faiyum depression south of the delta.

The Modern Nile Delta Continental Shelf, with an Evolving Record of Relict Deposits Displaced and Altered by Sediment Dynamics

“…The laterally wider extension of markedly higher heavy mineral concentrations (8-14%) on both sides of the presently still-active Rosetta promontory, and to the east of the Damietta branch and also off the ancient Sebennitic estuary, also confirm their natural displacement along the delta coastline (Figure 9). An example of this shift has been recorded for the Sebennitic channel that formed the remnant Sebennitic promontory, now the largely eroded and rounded Burullus bulge of the north-central delta [29,31]. The mouth of this branch (one extending to a depth of 18 m) shifted three times toward the west as a result of the progressive overall lowering of land relative to the sea level in this northern region, estimated at a rate of 7.7 mm per year [69].…”

“…On the delta plain, the path of the buried Canopic branch was traced using magnetic indications [26], Radar (SRTM) imagery [27], high-resolution seismic data, and short vibro-cores [28]. The Sebennitic and associated smaller distributaries that form the north-central deltaic Burullus bulge were mapped via satellite imagery and sediment cores drilled south of the present coast [29]. In addition, a number of now-extinct Nile distributary channels and delta lobes (Mendesian and Pelusiac) and the overbank deposits (Sebennitic) were interpreted in the delta plain from the petrologic analyses of numerous radiocarbon-dated core samples located landward of the present coastline [30,31].…”

“…Such deltaic deposits began to accumulate at approximately the time when the rate of sea level rise began to decelerate, from roughly 7500 yr BP to the late Holocene [31]. The mouth of the Sebennitic was once located further north, on what is now the inner to middle delta shelf [29,66].…”

“…It has been noted that the location and orientation of the identified lobes offshore do not in all cases coincide with most of the inland traces of former deltaic branches such as the Saitic, Sebennitic, Athribic, and Mendesian (Figure 9). This relative offset could be related to the continued lateral shifts of their estuaries mostly to the east, and some locally to the west [29]. This may have been caused by the effects of periodical reversals of wave-induced longshore currents or by other physical interventions on the seafloor, as shown in Figure 3.…”