A review of last interglacial sea-level proxies in the eastern Mediterranean coastal region

Mediterranean ‘raised beaches’ were subject to Quaternary research since the early years of the 20th century. The uniqueness of a warm-loving molluscs fauna immigrating into the Mediterranean made the coastline a prime interest for studying Quaternary sea-level changes. Today, we have a detailed picture of this historically important coastline characterised by tectonically dormant coastal zone alternating with zones that are subject to tectonic deformation. As part of the Word Atlas of last interglacial shorelines (WALIS) database we compiled 10 MIS 5e proxies for the eastern Mediterranean area available at http://doi.org/10.5281/zenodo.4454553 (Mauz, 2020). These datapoints are sea-level indicators of variable quality situated between 0±1 m and 12±10 m resulting in a reconstructed MIS 5e palaeo-sea level situated between 0±2 m and 13±10 m.


Introduction
The eastern Mediterranean area (Fig. 1) is a remain of the western Neotethys Ocean (Hafkenscheid and Spakman, 2006) which formed when the Indian Ocean gateway closed during the Miocene (Bialik et al., 2019).
It contains the oldest oceanic crust on earth (Granot, 2016) which is actively subducting beneath the Aegean Sea (Crete, Peleponnese peninsula) and the Ionian Sea (Calabria). The oceanic crust is part of the northeast moving African plate and the continental part of this plate is a passive continental margin. The coasts of the eastern Mediterranean are therefore situated on earth's crustal segments that are, on late Quaternary time scales, actively deformed, slowly deformed or dormant. Because the eastern Mediterranean has a long history of geoscientific work the actively deformed areas, such as the Gulf of Corinth, Crete and Cyprus are very well studied (e.g., McPhee and Hinsbergen, 2019;McNeill et al., 2018). These studies used, amongst other features, the relatively well-preserved last interglacial (LIG) marine terraces. On the other side, the coast of the African passive continental margin received attention through Quaternary scientist who aimed, in the first instance at least (e.g., Gignoux 2013), to carry forward the biostratigraphy of the late Tertiary owing to the fauna-rich coastal deposits.
Today, our understanding of the geodynamics (e.g., Nocquet, 2012) enables us to attribute the eastern Mediterranean coastal zones to large-scale geological structures (Fig. 1). This in turn enables us to separate shoreline data generated to unravel tectonic processes from sea-level data generated to reconstruct the LIG sea level and the associated ice volumes, eustacy and related GIA processes.
In this paper we describe previously published sea-level proxies on the basis of standards first developed by van de Plassche (1986) and Shennan, (1986) and recently updated in Shennan et al. (2015).

Literature overview
The overview follows the clockwise spatial arrangement of large-scale geological structures in the eastern Mediterranean ( Fig. 1) starting in the north. For the sake of clarity, we use names of eastern Mediterranean subbasins supported by names of nations. In terms of time we review literature which studied the "Tyrrhenian", a Mediterranean chronostratigraphic stage of the late Pleistocene that broadly encompasses the MIS 5 stage (Gibbard and Cohen, 2008). Historically, the Tyrrhenian stage has been identified on the basis of the so-called "Senegalese" fauna (Gignoux, 1913) which is an assemblage of warm-loving, shallow marine molluscs originating from the tropical Atlantic with the gastropod Strombus bubonius being its leading fossil. The Senegalese fauna immigrated into the Mediterranean during MIS 5 and disappeared with average sea-surface temperatures falling below 20°C (Sessa et al., 2013). Therefore, the assemblage disappeared most probably ~115 ka, but may have remained until ~80 ka in niches along the warm north African coast. McPhee and van Hindsbergen, 2019), the African passive continental margin (Nocquet, 2012), the zone affected by the Nile discharge (Emery and Neev, 1960;Davis et al., 2012) and the morphological lowlands which are graben or rift basins with minor or absent tectonic activity during the late Quaternary. The Gebco data were obtained from GEBCO Compilation Group (2020) GEBCO 2020 Grid (doi:10.5285/a29c5465-b138-234d-e053-6c86abc040b9). SRTM data were obtained from http://srtm.csi.cgiar.org (Jarvis et al., 2008).

Active tectonic zone
Black Sea (Turkey) -this area is connected to the Aegean Sea through the ~100 m deep Bosporus sill. The Turkish Black Sea coast is in most places affected by tectonic uplift of up to 5 mm/a with the exception of the Sile site where several mm/a subsidence seems to prevail (Avsar et al., 2017). The GIA contribution to vertical land movements is estimated to ~0-1 mm/a (Avsar et al., 2017). Erginal et al. (2017) describes a shell-rich sandstone ("coquinite") at Sile situated within today's beach zone and dated to around 128 ka.

Ionian Sea (Peloponnese peninsula, Greece) -this area is situated adjacent to the Hellenic trench and the
Kephalonia fault both being part of the Hellenic subduction zone. Athanassis and Foutoulis (2013) identify MIS 5 shell-rich littoral deposits on a "platform" with a palaeo-shoreline situated at ca 40 -60 m altitude.

Ionian Sea (Corinth Gulf, Greece)
-the gulf is a marginal sea connected to the Ionian Sea through two 50-60 m deep sills. It is affected by high to very high extension rates and associated uplift of coastal zones. A suite of marine terraces occurs on the southeast coast of the Gulf (Vokha plain) which attracted many researchers owing to the large number of terrace levels (16 terraces;de Gelder et al., 2019), their well-preserved topographic expression and coastal sediment cover. The early studies focused on the relationship between sea-level highstands and terrace elevation (e.g., Keraudren and Sorel, 1987;Collier, 1990) followed by studies looking at the terraces, their sediment cover and associated ages and at structural implications with the seminal paper published by Armijo et al. (1996). The researchers' interest focused on the understanding of the Corinth rift (e.g., Gawthorpe et al., 2018) and we refer the reader to De Gelder et al. (2019) for the most recent study of the terraces and to McNeill et al. (2018) for the interplay between rifting, sediment routing, climate and sea level.
Marmara Sea (Turkey) -this is a marginal sea connected to the Aegean Sea through a ca 70 m deep sill (Dardanelles). Two major branches of the North Anatolian fault (NAF) delimit the Marmara basin to the north and south forming the Marmara transtensional basin (Jenkins et al., 2020). The northern NAF strand creates deep tectonic depressions separated by structural highs (Jenkins et al., 2020). High rates of NAF motion (~20 mm/a) progressively increasing westward (Bulkan et al., 2020) and associated earthquakes makes the area a prime subject of hazard studies. Studying Pleistocene marine terraces in this area aims therefore at determining uplift rates and, in addition, the hydrodynamic history between the Black Sea and the Aegean Sea. Yaltirak et al. (2002) studied the marine terraces along the Dardanelles coast and finds the LIG terrace at 38-22 m and at 9-0 m.
Aegean Sea (Crete, Greece) -the Crete island is a subaerial forearc above the Hellenic subduction zone and thus, its shoreline-related features are used to study the geodynamics of the eastern Mediterranean (e.g., Robertson et al., 2019). The studies focus on the south coast of the island where the LIG marine terrace is situated at 116-45 m altitude (Robertson et al., 2019) and at 50-100 m altitude (Gallen et al., 2014). For the most recent study of the terraces see Ott et al. (2019) and references therein.

Levant Sea (Cyprus, Greece; Turkey)
-the Cyprus island is situated above the Cyprean subduction zone.
Similar to Crete, its marine terraces and related shoreline features are in the focus of structural geologists in order to understand the geodynamics of the eastern Mediterranean (e.g., McPhee and van Hinsbergen, 2019).

Ionian Sea (north Tunisia)
-the northernmost coast of Tunisia is part of the Alpine orogenic belt and associated tectonic processes. LIG deposits are part of cliff sections (Sahli et al., 2019) or marine terraces. Elmejdoub and Jedoui (2009) show that in NE Tunisia the LIG deposits are part of a marine terrace at ~25 m altitude.

Nile littoral cell and Nile delta
Levant Sea (Israel) -The central ("Carmel") coast is part of the passive continental margin of the African plate which moves southward along the Dead Sea transform fault (e.g., Weinberger et al., 2009). It receives its sediments exclusively through the Nile littoral cell (e.g., Davis et al., 2012) which is a persistent easterly-driven longshore current created by the interplay of winds and Coriolis force. Coastal deposits bearing Strombus bubonius were first described by Issar and Kafri, (1972) and subsequently defined as "Yasaf" member by Sivan et al. (1999). LIG deposits occur on the Carmel coast at -1 m up to 7 m (Galili et al., 2007; and on the Sharon coast at around -55 m (Porat et al., 2003).

African passive continental margin
Ionian Sea (Egypt) -the coast sits on the African plate with minor to negligible effects from tectonic movements on the LIG deposits. The coastal plain west of the Nile delta exhibits a series of beach ridges first described and dated by El-Asmar 1994 and later by El-Asmar and Wood (2000) and studied by Elshazly et al. (2019). The second ridge behind the modern coastline was attributed to MIS 5e.

Ionian Sea (Libya) -The coast from west of Alexandria (Egypt) to east of Tripoli (Libya) is under-studied and
Quaternary deposits are only known from Explanatory Booklet provided in association to geological maps.
Therein, Hinnawy and Cheshitev (1975) describe the "Gargaresh Formation" of "Tyrrhennian" age which forms an elongated ridge parallel to the modern shoreline.
Ionian Sea (Tunisia) -the coast is situated on the largest eastern Mediterranean shelf. Around Djerba island the LIG coastal environment is represented by a barrier stretching from Sabratah to the southern Gulf of Gabès (Fig. 4;Jedoui et al., 2003). A barrier also existed north of the Gabès gulf in the Gulf of Hammamet and along the south coast of Cap Bon. Coastal deposits were first systematically described by Paskoff and Sanaville (1983). Hearty (1986) provide the first age for the Monastir site (Fig. 5) through his seminal work on amino acid razemisation correlated to U-series ages. Subsequently, Queslati (1994) and Jedoui et al. (2003) studied the LIG deposits on the south coast situated at 2-6 m altitude. Later, Mauz et al. (2009) studied sedimentological details of the deposits and their ages.

Coastal lowlands
These coastal zones are morphological lowlands. Ongoing subsidence during the Quaternary is possible but not everywhere evident from data.

Haifa bay, Rosh Hanikra platform (Levant Sea, Israel) -the northern coast is situated between the Rosh
Hanikra fault and the Carmel fault. The Ahihud fault separates the Rosh Hanikra platform from Haifa bay. LIG deposits occur on the sediment-starved Galilee coast at elevations 1-2 m (Sivan et al., 2016), in Haifa bay at around -25 m ( Fig. 2; Avnaim-Katav et al., 2012). No onshore coeval deposit is reported from this bay (Zviely et al., 2006).

Gulf of Sirte (Libya)
-the gulf is part of a Cretaceous rift basin undergoing northward tilting and associated subsidence (van der Meer and Cloetingh, 1993). Giglia (1984) describes shallow marine oolitic limestone situated at around 3 m around 20 km inland.

Gulf of Gabès (Tunisia)
-the gulf is part of the collapsed Jeffara block dominated by normal faulting during the Quaternary (Gharbi et al., 2014). Shape and geometry of the gulf funnels the tidal wave with the consequence that the gulf coast experiences not only the highest tidal range in the Mediterranean (MHHW 2 m; Gzam et al 2016) but also unusual shore-parallel hyrodynamic conditions (Sammari et al., 2006;Gzam et al 2016). The LIG deposit is part of a beach ridge stretching parallel to the modern coastline at ca 3 m altitude (Gzam et al., 2016).

Sea-level indicators
Occurrence and preservation of sea-level indicators on the eastern Mediterranean coast is controlled by the morphology, sediment supply and geological structure of the particular coastal zone as well as by the human demand for coastal resources. Large zones of coast are deprived of indicators, e.g. the frequently cited zone at Monastir (Tunisia; e.g., Kopp et al., 2009). On rocky, sediment-starved coasts erosional indicators such as abrasion platforms and tidal notches prevail while on soft sediment coasts with sufficient sediment supply beach ridges, sandy beaches, barriers and spits prevail. Sediment-starved coasts show abiotic carbonate crusts and lithophaga borings or biotic, reef-like constructions generated by red algae (corallinacea), algal serpulids, coral (Cladocora caespitosa) or vermetids. Some of the indicators can provide small vertical uncertainties, for instance, if the living range of a particular fauna is small or if the sediment facies is well constrained in terms of water depth. The most important indicators are listed in Table 1.

Marine Terrace
The marine terrace is a gently seaward dipping surface typically covered by a veneer of coastal sediment. It typically occurs on uplifting (and subsiding) coasts where the interaction between wave action, hard-rock lithology and sediment starvation allow a wave abrasion platform to form during sea-level highstand. Because the inner margin, located updip of the terrace deposit, is often buried by terrestrial sediments, reconstruction of the maximum shoreline position is a challenge and requires digital elevation model ( techniques (e.g., GPR) are not employed, the marine terrace is considered marine-limiting or it is a sea-level indicator with an uncertainty deduced from the DEM resolution (e.g., 5 m).

Sediment Facies
Eastern Mediterranean coastal sediments are represented by beach or fan-delta conglomerate, siliciclastic, carbonate and oolitic sand, clay and silt. These sediments may constitute beach ridges, barriers, veneers on terraces, beaches, lagoons or sabkhas resting in coastal onlap architecture on a flooding or erosional surface. A coastal deposit is undifferentiated and, hence, marine-limiting if the depositional environment has not been determined. It is considered a sea-level indicator where facies determination allows inferring water depth ( Table   1). The indicative range of each sediment facies varies depending on the coastal topography, rate of sediment supply and prevailing hydrodynamics and must be determined for each site separately. With the small tidal range in the eastern Mediterranean the vertical precision of an index point deduced from sediment facies can be <50 cm in places. However, with the difficulty of dating, the number of high-quality facies-based indicators remains small.

Cladocora Caespitosa Reef
Cladocora caespitosa is a scleractinian polyp characterised by a corallite skeleton. It is a colonial coral species which forms banks of variable size on rocky and, occasionally, on sandy seabeds. The temperate coral is endemic to the Mediterranean where it shows relatively slow skeletal growth rates ranging from 1.3 mm yr −1 (Peirano et al., 2009) to 6.2 mm yr −1 (Kružic and Požar-Domac, 2003) mainly controlled by water temperature (Rodolfo-Metalpa et al., 2008). The colonies grow in shallow water and are rarely found below 30 m water depth (Kružić and Benkovic, 2008) and are therefore considered marine-limiting. Living and fossil C.
caespitosa colonies are reported for north and central Aegean Sea, Marmara Sea, Crete, Cyprus, Levant, Gulf of Gabès, north Tunisia and Strait of Sicily (Ozalp and Alparslan, 2011). The coral has been used predominantly for the purpose of U-series dating the associated LIG deposits with limited success however, likely caused by the strong seawater temperature dependence (Trotter et al., 2011) and associated crystal instability of carbonate minerals secreted by the coral compared to their tropical counterparts.

Eastern Mediterranean LIG sea-level sites
In total 10 indicators are compiled and displayed against their longitudinal position in Fig. 2. When taking the uncertainty into account, the minimum and maximum LIG sea level is at -1.5 m and 23 m, respectively. The 10 indicators displayed in Fig. 2 are situated on coastal zones affected by the interplay of eustacy and associated regional GIA only and provide age constraints and/or the Senegal fauna. Zones with minor or debated non-GIA contributions are also included. Coastal zones for which non-GIA processes during the late Quaternary are unambiguously evident are excluded (for zones see Fig. 1). For the selected zones we assume coastal geometries, hence tidal prism similar to today because the course of the LIG beach ridges and barriers suggest a LIG coastline running sub-parallel to the modern one. The tidal regime in the eastern Mediterranean is dominated by the equilibrium tide modified by the incoming Atlantic wave (Tsimplis et al., 1995). Generally, the mean tidal range today is 0.5 m (Admiralty Tide tables) apart from the Gulf of Gabès (1.5 m mean tidal range; Gzam et al., 2016). The mean tidal range is modified spatially by land-ocean distribution (e.g., northern Aegean Sea) and seasonally by ocean swell in winter.

Black Sea rift zone
Sile (ID 927; Fig. 1) -the around 80 cm thick cemented, moderately sorted bioclast-rich sand ("Coquinite"; Erginal et al. 2017) shows seaward dipping laminae in its lower part and tabular planar cross-beds in its upper part; depositional environment is foreshore to beach (Erginal et al., 2017). The deposit is situated at 0±1 m.
Assuming a virtual absence of tides in the Black Sea (Medvedev et al., 2016) and an operational Bosporus gateway during LIG, this is a facies-based sea-level indicator with an indicative range of 0-2 m water depth. The palaeo-sea level is at 0.0±1.5 m at 127±9 ka (Erginal et al., 2017). The site is affected by subsidence estimated to ~2.3 mm/a for the most recent period (2008-2014) of the instrumental record (Avsar et al., 2017).

African passive continental margin zone
El-Max-Abu Sir (ID 1362; Fig. 4) -The LIG shoreline is represented by the second beach ridge behind the modern coastline. Cross-bedded bioclastic and oolitic grainstone of foreshore depositional environment (Elshazly et al., 2019) constitute the basal part of the ridge. The elevation should be < 5 m but is poorly defined.

Ras Karboub
Khniss (ID 1364; Fig. 6) -This site is part of the Hammamet barrier stretching almost parallel to the modern coastline from Chebba to ID 926. The barrier shows siliciclastic sand of shoreface to foreshore environment gradually passing into oolitic grainstone of foreshore environment (Jedoui et al., 2003;Mauz et al., 2009). The elevation should be 5-10 m but is poorly defined. This is a facies-based sea-level indicator with an indicative range of +1m to -3 m. The palaeo-sea level is at 12±4 m at 121±10 ka (Mauz et al., 2009). Fig. 6) -the around 2 m thick cemented bioclastic quartz sand shows planar laminae; the depositional environment is foreshore (Mauz et al., 2018). The elevation of the corresponding shoreline should be at 3-2 m deduced from the altitude of the coeval lagoonal deposit (Mauz et al., 2018). This is a facies-based sea-level indicator with an indicative range of 1-3 m water depth. The palaeo-sea level is at 4.2±1.8 m at 120±5 ka. Fig. 6. The westernmost Ionian Sea coast (Tunisia). The datapoints included in the WALIS database are depicted with their WALIS ID. Gebco data were obtained from GEBCO Compilation Group (2020) GEBCO 2020 Grid (doi:10.5285/a29c5465-b138-234d-e053-6c86abc040b9). SRTM data were obtained from http://srtm.csi.cgiar.org (Jarvis et al., 2008).

Coastal lowlands
Gulf of Gabès (ID 1365; Fig. 5) -The LIG deposit is part of a coastline-parallel beach ridge. The lower part of the ridge is characterised by planar laminated beds of bioclastic sand bearing Strombus bubonius fossil remains (Gzam et al., 2016). The deposit is situated at 3 m (Gzam et al., 2016). This is a facies-based sea-level indicator with an indicative range of +0.5 m to 0 m including 1.5 m mean tidal range. The palaeo-sea level is at 1.5±3.4 m during MIS 5e.

Alpine orogenic belt
Korba (ID 1366; Fig 6) -This site is part of the Cap Bon barrier stretching almost parallel to the modern coastline ). The barrier shows siliciclastic sand in cross-bed or foreset bedding bearing Strombus bubonius in places ). The depositional environment is foreshore to beach Mauz et al., 2012). The elevation should be 5-10 m but is poorly defined. This is a facies-based sea-level indicator with an indicative range of +1 m to -3 m. The palaeo-sea level is at 13±10 m during MIS 5e. Fig. 6) -the indicator is part of a cliff section the lower part of which is characterised by planar laminated beds of bio-and siliciclastic sand of shoreface to foreshore environment (Mauz et al., 2009).

Rass Zebib (ID 1368;
The elevation should be around 5 m but is poorly defined. This is a facies-based sea-level indicator with an indicative range of -3 m to -8 m. The palaeo-sea level is at 11±6 m at 131±7 ka (Mauz et al., 2009). (ID 1367; Fig. 6) -the indicator is part of a cliff section the middle part of which is characterised by low-angle cross bedded bioclastic calcarenites (Sahli et al., 2019). The depositional environment is foreshore.

Ras el Korane
The elevation should be 5-6 m but is poorly defined. This is a facies-based sea-level indicator with an indicative range of -1 m to -5 m. The palaeo-sea level is at 8±5 m during MIS 5e as deduced from facies correlation (Sahli et al., 2019).

Quality of data
All sea-level indicators are facies-based and characterised by relatively small indicative ranges owing to the small tidal ranges on the respective coastal zones. The uncertainty of the indicator is high owing to poorly constrained elevation data. Because facies relationships and coastal architecture is also poorly defined in most sites, the indicators are generally of medium to low quality. There are two exception to this: the Nahel Me'arot site (ID 3636) and the Hergla site (ID 926). Both sites are characterised by well-understood facies architecture and facies relationship (Hearty et al., 2007;Galili et al., 2007;Mauz et al., 2012Mauz et al., , 2018. The Hergla coastal barrier is situated at the modern coastline where it forms a cliff suggesting subsidence and/or effects of dynamic topography impacting on today's elevation of the former barrier. The Nahel Me'arot site is situated behind the modern coastline. The Holocene GIA model data suggest that the LIG sea-level position deduced from this site is of high quality (see below).

Impact of GIA mechanisms on the LIG shoreline elevation
The Mediterranean coast is a medium field relative to the former ice sheets and is therefore less sensitive to ice volume uncertainties. The Holocene modelling work indicates that some areas are relatively insensitive to earthmodel parameter choice ( Fig. 7; Lambeck et al., 2004;Lambeck and Purcell, 2005;Stocchi and Spada, 2007).
Region 5 (Fig. 7) is suitable for sea-level reconstruction even if the predicted RSL deviates from the far-field eustatic curve because its insensitivity coincides with negligible surface deformation. Because parts of region 5 are affected by non-GIA deformation (e.g., Marmara Sea, Gulf of Sirte, Gulf of Gabès) suitable coastal zones in the eastern Mediterranean are located on the Levant coast and on the southern Ionian coast (Libya). Fig. 7. RSL regions for t < 9 ka. Data are compiled from Lambeck and Purcell (2005) and Stocchi and Spada (2007) using ice models ICE3G, ICE5G, ICE1+A3, NE1, NE2, NA1, NA2. All models assume cessation of melting at 6 ka. Numbers indicate Holocene sites representing the corresponding RSL region.
Similar to other mid-latitudinal coastal areas (e.g., US-Carolina coast; Parham et al., 2007) controversies exist on the position of the MIS 5 shorelines. In fact, only few sites show the LIG shoreline at the commonly expected 6 m altitude (Fig. 2). Furthermore, for the MIS 5a Dorale et al. (2010) indicate that the shoreline in the West Mediterranean should have been close to modern MSL, but at Hergla (ID 926) the shoreline is at ~4 m (Mauz et al., 2018). Following results from geophysical modelling (e.g., Creveling et al., 2015) even the farfield shoreline can depart by up to 4 m from the eustatic value owing to local dynamic topography (e.g., Austermann et al., 2017). On the other hand, the LIG eustatic level is reconstructed probabilistically with a 4 m uncertainty (Kopp et al., 2013). Transferring these findings to the eastern Mediterranean, we can say that on tectonically dormant coasts the LIG sea level must have been situated at 5 ± 8 m. In fact, all our datapoints depicted in Fig. 2 fall in this range suggesting that reliable sites were selected in this review. The sites ID3636, 1362, 1363 and 1364 are in line with the GIA predictions for the Holocene. The mean LIG sea-level position deduced from these sites is 8.3±12.6 m. It is probable that this value is accurate but its precision requires more analytical effort regarding elevation and facies.