Late Holocene erosion of the Canopic promontory (Nile Delta, Egypt) Clément Flaux a , Nick Marriner b, ⁎, Mena el-Assal c , David Kaniewski a,d , Christophe Morhange e a CNRS, EcoLab (Laboratoire d'Ecologie Fonctionnelle et Environnement), Toulouse, France b CNRS, Laboratoire Chrono-Environnement UMR 6249, MSHE Ledoux, USR 3124, Université de Bourgogne-Franche-Comté, UFR ST, 16 Route de Gray, 25030 Besançon, France c King Khalid University, 1, Guraiger, Abha 62529, Saudia Arabia d Université Paul Sabatier-Toulouse 3, EcoLab (Laboratoire d'Ecologie Fonctionnelle et Environnement), Toulouse, France e Aix-Marseille University, CEREGE, IUF, Aix-en-Provence, France abstract article info Article history: Received 7 July 2016 Received in revised form 16 November 2016 Accepted 17 November 2016 Available online 22 November 2016 The mouths of the Nile Delta are sensitive coastal areas, their geomorphology primarily being mediated by rela- tive sea-level rise and sediment supply. To further document the Holocene evolution of the Nile's Canopic mouth, a core was taken from the southern shores of Abu Qir Bay, close to the ancient Canopic channel. Core bio-sedi- mentology and chronostratigraphy highlight four stages of marine incursion which are juxtaposed upon the gen- eral progradation trend of the Nile coast in this area. Compiled age-depth points from sediment cores taken in Abu Qir Bay underscore two phases of negative sediment budget at the Canopic mouth: (1) a first period, be- tween 3.5 and 2 ka cal. yr BC, probably in relation to the well-documented mid-to-late Holocene decline in Nile flow; and (2) a second phase, after 0.5 ka cal. AD, linked to a decline in Canopic sediment supply to the coast- al area, and concomitant with the development of the Rashid branch. The erosion and reworking of material flat- tened and lowered the promontory surface by up to 4 m. The submersion of the Canopic promontory was completed by relative sea-level rise, primarily controlled by the compaction and liquefaction of unconsolidated lagoonal muds. The lowering of the Canopic mouth led to the submersion of two ancient estuarine-harbor cities, known as East-Canopus and Herakleion, whose remains lie 4–7 m below present mean sea level. It is argued that the subsidence of the two cities cannot explain their abandonment during the late 7th–early 8th century AD, tak- ing into account the regional occupation pattern during Antiquity. Rather, the longevity of the two cities, span- ning more than 13 centuries, shows that adaptation to coastal risks including erosion, subsidence and high- energy events like storms or tsunamis, was the rule. © 2016 Elsevier B.V. All rights reserved. Keywords: Holocene Delta Lobe River mouth Sea level Subsidence Sedimentary budget Geomorphology Geoarcheology Human paleogeography Herakleion East-Canopus Nile Egypt 1. Introduction Human populations living on deltaic coasts are increasingly vulner- able to flooding, primarily mediated by a combination of rising relative sea level and decreasing sediment supply to coastal depocenters (Anthony, 2009; Anthony et al., 2014). The relative contribution of pres- ent global sea-level rise (1.8 mm yr -1 ; Church et al., 2011) is now con- sidered to be minor when compared to local subsidence processes and reduced deltaic plain aggradation (Syvitski et al., 2009; Stewart and Morhange, 2009). The Nile delta is a prime example of a coastline prone to sinking and its vulnerability has been regularly underlined by scholars (e.g. Stanley and Warne, 1993; Stanley et al., 2001; J.-D. Stanley et al., 2004; Nicholls et al., 2007; Syvitski et al., 2009; Frihy et al., 2010; Marriner et al., 2013). In particular, the Nile's promontories appear to be very sensitive (Frihy and Lawrence, 2004). Modern subsi- dence rates, estimated using radar interferometry data on the Damietta promontory, are as high as 6–8 mm yr -1 , while values of 0–5 mm yr -1 have been measured on the adjacent delta plain (Becker and Sultan, 2009). Between 1922 and 2000, the western Rashid promontory retreated at a mean rate of 43 m yr -1 (Frihy and Lawrence, 2004), reaching a peak of 100 m yr -1 between 1971 and 1990 (Frihy and Komar, 1993). The transition from a state of accretion to erosion oc- curred in the early 20th century, when sediment delivery to the mouth declined sharply, due to the Nile's upriver dams (Frihy and Lawrence, 2004) and the very dense canal and drainage network acting as a huge sedimentary trap (Stanley, 1996). Older deltaic promontories provide the opportunity to analyze the sensitivity of these coastal features to long-term changes in Nile sedi- ment supply. Among the seven mouths of the Nile reported in Antiquity (Toussoun, 1922, 1926), only two are still active at present (Rashid and Damietta). The others have been buried below lagoon muds (eastern delta) or eroded and reworked along beach ridges (western and north- ern delta) (Stanley and Warne, 1993). Nile promontories are thus short- lived deltaic depocenters at the late-Holocene timescale. Because the geomorphological response of the modern Rashid and Damietta mouths to Nile hydro-sedimentary changes has been severe, it is hypothesized that the reconstruction of past promontory evolution can help to Marine Geology 385 (2017) 56–67 ⁎ Corresponding author. E-mail address: nick.marriner@univ-fcomte.fr (N. Marriner). http://dx.doi.org/10.1016/j.margeo.2016.11.010 0025-3227/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Marine Geology journal homepage: www.elsevier.com/locate/margo