Quantifying spatial variability in shell midden formation in the Farasan Islands, Saudi Arabia

Abstract

During the past decade, over 3000 shell middens or shell matrix deposits have been discovered on the Farasan Islands in the southern Red Sea, dating to the period c. 7,360 to 4,700 years ago. Many of the sites are distributed along a palaeoshoreline which is now 2–3 m above present sea level. Others form clusters with some sites on the shoreline and others located inland over distances of c. 30 m to 1 km. We refer to these inland sites as ‘post-shore’ sites. Following Meehan, who observed a similar spatial separation in shell deposition in her ethnographic study of Anbarra shellgathering in the Northern Territory of Australia, we hypothesise that the shoreline sites are specialised sites for the processing or immediate consumption of shell food, and the post-shore sites are habitation sites used for a variety of activities. We test this proposition through a systematic analysis of 55 radiocarbon dates and measurement of shell quantities from the excavation of 15 shell matrix sites in a variety of locations including shoreline and post-shore sites. Our results demonstrate large differences in rates of shell accumulation between these two types of sites and selective removal of shoreline sites by changes in sea level. We also discuss the wider implications for understanding the differential preservation and visibility of shell-matrix deposits in coastal settings in other parts of the world extending back into the later Pleistocene in association with periods of lowersea level. Our results highlight the importance of taphonomic factors of post-depositional degradation and destruction, rates of shell accumulation, the influence on site location of factors other than shell food supply, and the relative distance of deposits from their nearest palaeoshorelines as key variables in the interpretation of shell quantities. Failure to take these variables into account when investigating shells and shell-matrix deposits in late Pleistocene and early Holocene contexts is likely to compromise interpretations of the role and significance of shell food in human evolutionary and socio-cultural development.

Mid-Late Holocene Paleoenvironmental and Sea Level Reconstruction on the Al Lith Red Sea Coast, Saudi Arabia

“…The change to intertidal conditions occurred at 3100 cal.year BP at Matar-1, and probably represents the fall in sea level as the intertidal and supratidal successions prograded over the lagoonal sequence at this site. This is confirmed by the presence of lower elevation middens closer to the present coast dating from 2300 to 1500 cal.year BP (Hausmann et al, 2019).…”

“…However, the change from subtidal to beach at +1.68 m may indicate the maximum elevation of the highstand sea level since it is close to the best predicted maximum Holocene sea level at 5000 cal.year BP (+1.5 m) at the Farasan Islands (Hein et al, 2011;figure DR2). This also corresponds to the occurrence of mid Holocene shell middens on the islands that are 2-3 m above present sea level and date from 6000 cal.year BP (Hausmann et al, 2019). The change to intertidal conditions occurred at 3100 cal.year BP at Matar-1, and probably represents the fall in sea level as the intertidal and supratidal successions prograded over the lagoonal sequence at this site.…”

67,000 years of coastal engagement at Panga ya Saidi, eastern Africa

“…It is also possible that the oysters were processed at the point of acquisition, with the meat removed and preserved, and the shell discarded prior to transportation inland, either carried directly or indirectly via trade networks [ 91 , 92 ]. As noted by Hausmann et al [ 93 ], even over long distances, the byproducts of field processing (i.e., the shell) should still conform to expectations of transport constraints with shell density decreasing with greater distance from the source [ 72 ]. Importantly, the major peak in Ostreidae density in Layer 4 (8 kya, 544.8 NISP/m 3 ) corresponds with sea levels approximating modern levels.…”

Beyond consumption and discard: A comparative sedimentological analysis of two shell deposits from Albatross Bay, Australia, and the Farasan Islands, Saudi Arabia

“…Since then the DISPERSE project has mapped over 3000 shell mounds ranging in thickness from less than 1 m to over 5 m, often forming clusters around shallow bays, and conducted excavations at 19 of them (Bailey et al, 2013a(Bailey et al, , 2013bMeredith-Williams et al, 2014, 2018. Radiocarbon determinations indicate that most of the shell material accumulated between 7400 and 4700 cal BP (Hausmann et al, 2019). The dominant taxon throughout is the small gastropod Conomurex fasciatus (Born, 1778), although other taxa are also quite common and occasionally dominate in individual layers.…”