A standardized database of MIS 5 e sea-level proxies in southern Africa ( Angola , Namibia and South Africa )

Evidence for sea-level change during and around Marine Isotopic Stage 5e (ca. 125 ka) in southern Africa derives from a wide variety of geomorphic and sedimentological sea-level indicators, supported in the past 2 decades by absolute chronological control. In addition to these proxies, data provided by both terrestrial (dune sediments and archaeological remains) and marine (lagoonal and 10 nearshore littoral sediments) limiting points provide broad constraints on sea level. Here, we review publications describing these data points. Using the framework of the World Atlas of Last Interglacial Shorelines, we insert in a standardized database all the elements needed to assess former paleo relative sea level, and the chronological constraints associated with them (including uncertainties). Overall, we reviewed 69 studies, from which we extracted 35 sea-level indicators and 25 limiting points. 15 As far as age attribution is concerned, early dating of molluscs and whole-rock beachrock samples using U-Series allowed ating of several sea-level indicators during the 1980s but the more widespread application of Optically Stimulated Luminescence dating since 2004 has yielded many more (and more accurate) dates from several sites. This has helped resolve the nature and timing of MIS5e shorelines and has the potential to further elucidate the apparent presence of two or more sea-level peaks at several 20 South African sites during this interval. The standardized sea-level database presented in this paper is the first of its kind for this region. Future research should be directed to improve the stratigraphic description of LIG shorelines and to obtain better dating, high-accuracy elevation measurements with better palaeo-RSL interpretation. https://doi.org/10.5194/essd-2020-166 O pe n A cc es s Earth System Science Data D icu ssio n s Preprint. Discussion started: 25 August 2020 c © Author(s) 2020. CC BY 4.0 License.

. The A beach at +2-3 m is likely of Holocene age but no absolute dating control has been established on shorelines A, B or C. 165 In Angola, Soares do Carvalho, (1961) first identified several marine terraces at various elevations above present sea level. These had littoral deposits resting upon them and as in Namibia, terraces and overlying deposits were considered to be broadly coeval. Giresse at al. (1984) reported U-Series dates on a number of these terraces at elevations between 0 and 55 m near Benguela and Lobito (Fig. 1). Of 170 these, three dates, deemed by the authors to be acceptable, were in the MIS 5 range. Mollusc samples from a +10-12 m terrace dated to 91 and 136 ka, and from a +20 m terrace to 103 ka. These provided little additional insight into the chronology of the Angolan shorelines which remained enigmatic. Walker et al. (2016) identified a widespread terrace at +25 m elevation that dated to 45 ka (based on 8 OSL dates). This demonstrated late Pleistocene dynamic uplift of the Angolan coast by ca. 300 m (ca. 2 175 mm/yr) via a mantle done with diameter of ca. 1000 km, centred on Benguela. This finding of substantial tectonic deformation along the Angolan coast, effectively requires a reappraisal of the ages and elevations of all shorelines in Angola, that has yet to be undertaken.
We note that our database contains information on paleo relative sea levels. The "relative" term 180 highlights the fact that every paleo sea level we report is uncorrected for potential post-depositional uplift or subsidence due to, for example, tectonics or glacial isostatic adjustment. Although the South African coast is regarded as tectonically stable during the Quaternary, the potential of tectonics on raised shoreline elevation has also been raised in northwestern South Africa (Namaqualand) and Namibia. Roberts and Brink (2002) reported deformation of Miocene and Pliocene shorelines on the 185 NW coast of South Africa involving ca. 50 m vertical displacement. Raised beaches in the southern Sperrgebiet (southern Namibia, Fig.1) said to be of Plio-Pleistocene age appear to diminish in altitude from south to north (Stocken, 1978;Dingle et al., 1983) and may imply recent deformation. Pickford and Senut (2000) note, however, that some of the Sperrgebeit shorelines may be as old as Miocene and the appearance of tilting could be an artifact. In reviewing existing studies, we identified several types of last interglacial sea-level indicators (Table   1). All are sedimentological (based on distinctive sedimentary facies that are diagnositic of particular coastal and terrestrial environments) and their indicative meaning (i.e., the relationship between the elevation of the indicator and the paleo relative sea level it represents) can be inferred by comparison 195 with their modern equivalents within certain error limits. The most widespread indicators are marine terraces that sometimes have associated littoral deposits. Although they can be related to former sea levels by comparison with modern equivalents, few of these, however, have been dated. Many estuaries and lagoons contain brackish water back-barrier sediments with distinctive molluscan faunas of which several are known to exist in a quantifiable relationship to sea level (Kilburn and Rippey, 1982). While 200 many supposed MIS5e estuarine deposits have been reported and described in the regional literature, few of these have been studied in detail using modern dating techniques, nor with detailed sedimentological investigations that might provide higher definition relationships to former sea levels.
The most valuable (with best chronological and elevation constraints) Index points from the region are provided by a variety of preserved littoral deposits with a quantifiable relationship to sea level at the 205 time of deposition. These include tidal inlet, foreshore and beachrock facies (Table 1). These can be linked to the sea-level at which they formed by comparison with modern equivalents, however, there is some variability in the vertical range in which each facies occurs. Tidal inlet and foreshore facies can only be constrained within a few metres of former sea-level, whereas beachrock can provide sub-metre constraints. The database also includes some broad indicators that simply record whether sea level was 210 higher or lower than the dated sample. These include terrestrial limiting dates set by aeolianites (nowcemented aeolian dunes that formed by wind action on dry land) or marine limiting dates set by undifferentiated foreshore/shoreface sediments that formed at an unknown depth below sea level in the marine environment.

Elevation measurements
The reviewed studies report elevations measured by either barometric altimeter (limited to early studies), levelling, echo-sounding, or do not report the elevation measurement method. As a 220 consequence, the sea level datum to which the data is referred to is usually not reported, and has been assumed to be Mean Sea Level. Spring tidal range around southern Africa is generally less than 2 m but more precise recording and reporting of the relationship of former littoral deposits to contemporary sealevel (and preferably a fixed datum with a known relationship to modern sea level) is desirable in future studies in order to reduce vertical uncertainties. 225 Nahoon points to two highstands, an older event at ∼2 m amsl and a younger counterpart at ∼6 m amsl". Although many potential MIS 5 deposits have been reported from the open coast and estuaries of the Eastern Cape, the only other dated evidence comes from a site at Coffee Bay (Fig. 1), where an oyster shell from a beach whose base is at +4.5 m yielded a U/Th age of 104.9 +/-9 ka (Ramsay and Cooper, 2002). 290

Namibia
The geological and sediemntological literature on the Nambian coastal deposits is quite extensive, but none of the literature surveyed meets the minimum database standards for MIS 5e sea-level quantification. The potential 5e sites reported in the literature lack absolute dating control; to our 310 https://doi.org/10.5194/essd-2020-166

Angola
Early U-Series dates presented by Giresse et al. (1984)  Uncertainties related to dating refer mainly to U-Series dates. These are sometimes at odds with other dating methods and suggest issues with the source material (not from closed systems, for example).
OSL dating in contrast, seems to have given more consistent results. The OSL dates, are, however, on 400 sandy sediments from the high energy coast where vertical uncertainties (see above) are comparatively highMany of the U-Series dates are from estuarine sediments where vertical uncertainties on sea-level indicators could potentially be better constrained due to the lower energy conditions in which they accumulate and the specific vertical ranges of certain organisms.
A mandatory evaluation of of data quality is included with each RSL datapoint. This was undertaken 405 following the WALIS guidelines.     Preprint. Discussion started: 25 August 2020 c Author(s) 2020. CC BY 4.0 License. Figure 6. Key sites in South Africa with sedimentary, but not fully dated records suggestive of two sealevel peaks during MIS5e. Locations on Fig. 1. a). Undated sequence exposed at Swartklip, (after Barwis and Tankard, 1983). The lowermost beach sequence represents a possible MIS5e highstand,