Cabu by the Sea Phase 3 New Romney: Geoarchaeological Borehole Survey and Deposit Modelling

A programme of geoarchaeological borehole survey and deposit modelling was undertaken to assess the geoarchaeological potential of the superficial deposits at Cabu by the Sea Phase 3. A total of 2 rotary boreholes were undertaken on the Site in the footprint of proposed cabins 26 and 27 (WA01 and WA02). A programme of geoarchaeological deposit modelling was subsequently undertaken, integrating the results of the new geoarchaeological borehole survey with existing GI data, resulting in a total of 12 data points for the deposit model. The results of the work identified a sequence of superficial deposits comprising of sandy interridge deposits underlain by coastal gravels associated with the Dungeness Foreshore Barrier Gravel, with the interface between the two units being encountered at 4.30m OD in WA01 (0.40m bgl) and at 4.17m OD (0.38m bgl) in WA02. Whilst the archaeological and palaeoenvironmental potential of the barrier gravel is low, the unit is of geomorphological significance, with the unit providing an important insight into patterns of mid to late Holocene coastal change, barrier evolution and the interrelationship to the back-barrier environment of New Romney. The base of the Dungeness Foreshore Barrier Gravels was not encountered during this phase of works, but the unit is known to be overlying tidal flat deposits of probable Late Holocene age at a depth c. 4.00-4.50m bgl from previous geoarchaeological investigations within the Site (Wessex Archaeology 2023). The tidal flat deposits are below the depth of impact for the proposed works (2.00m bgl) and the archaeological and paleoenvironmental of these deposits is considered low. The Dungeness Foreshore Barrier Gravels young regionally to the east and the barrier gravels identified within WA01 and WA02 are probable to be geologically young, with the evolution of the foreshore rapidly prograding eastwards c. 2 kya (Long et al. 2007). Although organic and peat rich units appropriate for palaeoenvironmental analysis have been identified within the interridge deposits of the Dungeness Foreland elsewhere in Romney and Welland Marsh, no such deposits were encountered within WA01 and WA02; this is consistent with previous investigations within the Site (Kirby 2013, Wessex Archaeology 2023). The likelihood of organic interridge deposits being present within the Site is considered low. Shell-rich subunits of the barrier gravels were identified within the prior geoarchaeological borehole survey (Wessex Archaeology 2023) at a minimum depth of 2.76m OD (2.00m bgl) in the north-east of the Site (BH1), with the top of the subunit being encountered at 0.87m OD (4.00m bgl) and 1.89m OD (2.65m bgl) in BH6 and BH8 respectively in the centre of the Site (Figure 1). No shell-rich subunits were encountered within WA01 or WA02, however these boreholes terminated at 2.40m OD and 2.25m OD respectively; the possibly of this unit being present at a depth below the investigation depth cannot be discounted from this phase of works. These deposits should not be impacted at the proposed depth of impact for the construction works but have a moderate possibility of being present by 3.00m bgl. Shell-rich deposits may be appropriate for AAR (Amino Acid Racemisation) dating and are of moderate geoarchaeological interest. As noted from the prior geoarchaeological borehole survey within the Site (Wessex Archaeology 2023), whilst the proposed development will impact the Dungeness Foreshore Barrier Gravels, the geomorphology of the barrier gravel topography at the Site and the deposits investigated are consistent with the immediate area within the Dungeness Foreland SSSI, and are therefore not in themselves unique, being typical of barrier deposits present elsewhere in the SSSI. There are no indications that the gravel in the impact area of the proposed development is unique within the SSSI.