Fig 1.
Elevation map of the Farasan Islands, showing the spatial distribution of shell midden sites.
Blue dots are shoreline middens, yellow dots are post-shore sites. The three transects with the sites selected for detailed radiocarbon dating are all in Janaba Bay and are shown in red. We refer to these as Janaba West (1), Janaba West-Central (2), and Janaba East (3).
Fig 2.
The edge of the coral platform in Janaba East, showing a notch deeply undercut by marine erosion.
Above it is a shell mound located with two figures standing on it. This undercut terrace is of variable extent along the Janaba Bay shoreline and is not present on the shoreline in the background nor associated with the sites in Transects 2 and 3, where the shallow gradient onshore and offshore has resulted in an almost imperceptible break between the landward surface of the fossilised coral platform and the offshore surface, Photo by Garry Momber, May 2006.
Fig 3.
Sample transects showing the locations of radiocarbon-dated shell-midden sites superimposed on satellite imagery.
Shoreline sites are indicated with a circle, post-shore sites are indicated with squares. Shorelines are indicated as follows: M: main shoreline, continuous black line; P: peak shoreline, dashed black line; L: lower shorelines, of which there are three in Transect 2, roughly parallel with the main shoreline as indicated by the square bracket.
Fig 4.
Shell mounds on the west side of the large inlet in Janaba West (Transect 1).
Photograph taken facing North-West, the low cliff at the edge of the coral platform on which the mounds sit is clearly visible on the left and represents the palaeoshoreline contemporaneous with the accumulation of the shell mounds. It is not nearly as deeply undercut as elsewhere because of erosion and partial collapse of the original overhang. It is probably the result of localised tectonic uplift that postdates the shell mounds and is not present on the palaeoshorelines elsewhere around this bay, for example in the Janaba central cluster. In the foreground are sandy deposits which extend out from the palaeoshoreline into what was originally a marine inlet. Photo by Geoff Bailey, March 2008.
Fig 5.
Post-shore shell scatter in the Janaba East cluster associated with Transect 3.
The site appears to be a low mound with a deflated shell scatter on the surface and coral blocks representing the remains of structures but has not been excavated or dated. Photograph taken facing West, shell mounds along palaeoshorelines are clearly visible in the distance. To the right is the shell scatter of JE5641, identifiable by the patch of red material, which is the spoil heap from the trench excavated into this deposit. Photo by Geoff Bailey, February 2013.
Fig 6.
(a) Shallow post-shore shell scatters found close to circular patterns of burnt material in the Janaba East cluster with shell mounds on the main shoreline visible in the distance; b: close up of multiple burnt areas–scale is 3 m. Photo by Niklas Hausmann, February 2013.
Fig 7.
Deflated post-shore site in foreground comprised mainly of shells of the large mollusc, Chicoreus ramosus.
A second shell scatter is visible in the left middle distance (JE5641). Photograph taken facing South, the large shell mound JE0086 on the main shore is visible in the distance to the right (with a trigonometrical pillar on its summit). A row of shell mounds on the main shoreline extends to the left of JE0086 (see also Fig 6) and a row of peak shoreline sites (incl. JE0087) is found to the far left of the image (see also Fig 3). Photo by Geoff Bailey, May 2006.
Fig 8.
Mound JE0078 on the main shoreline of the Janaba East cluster (Transect 3) after excavation, showing ash lenses clearly visible in section.
The white shell matrix in the upper deposit is dominated by shells of C. fasciatus, the darker shell matrix in the lower layers has a higher proportion of the large gastropod, Chicoreus ramosus. Photo by Geoff Bailey, January 2013.
Fig 9.
Site JW5697, one of the low-shore middens in the Janaba West-Central cluster on transect 2.
The shell matrix is dominated by shells of Chicoreus ramosus and sits directly on a thick beach deposit. Photo by Niklas Hausmann, February 2013.
Fig 10.
All radiocarbon dates grouped chronologically and by spatial group.
Dating convention as in Table 1.
Table 1.
Radiocarbon dates used for calculating the time depth and accumulation rates for all sites.
Dates are shown as calibrated years BP (95.4% confidence interval) following Bronk Ramsey[69]. All dates are calibrated using Oxcal (version 4.3.2) and the corresponding curves for terrestrial (IntCal13) or marine (Marine13) samples as appropriate [70] with a local reservoir correction of 188±44 years. Sites are grouped by type of location, within each location type in order of earliest deposits, and within each site by stratigraphic order from lowest to highest deposits.
Table 2.
Depth of deposit and accumulation rates in m per thousand years (ka) based on the difference between depths of lowest and highest radiocarbon samples within each site.
Fig 11.
Accumulation rates ordered by site type.
Exact rates are shown in Table 2. ‘Lower’ shoreline sites (JW5694, JW5719, JW5697) are excluded as they fall outside the main phase of shellfish gathering.