Dorit Sivan

Holocene sea-level changes along the Mediterranean coast of Israel, based on archaeological observations and numerical model

Local sea-level curves reflect global eustatic changes, regional isostatic adjustments of the crust to changing ice and ocean volumes and tectonically controlled crustal movements. In this study, we evaluate the relative contribution of each of these factors to the Holocene sea-level curve of the Mediterranean coast of Israel. We use archaeological data as constraints on palaeo sea levels and we then compare the observational limits with isostatic models for sea-level change across the region. The isostatic model includes the contribution arising from the relative minor increase in ocean volumes for the past 6000 years due to residual melting of ice sheets, the effect of the changing shape of the ocean basin, the time dependence of shorelines as sealevel changes and the changing surface area occupied by ice sheets. Differences, if significant, between the observed and predicted change are interpreted as being of tectonic origin. The archaeological observations and the model sea-level curve, along the Mediterranean coast of Israel were found to be generally consistent and any discrepancies lie within the uncertainties of both values. Our model predicted that 8000 years ago sea level at the Israel coast was at about 213.5 ^ 2 m, whereas the archaeological data place it at 216.5 ^ 1 m. By 7000 BP the predicted level has risen to about 27 ^ 1 m consistent with the archaeological evidences. According to both observations and predictions sea level was still lower than 2 3t o24.5 m at 6000 BP and remained below its present level until about 3000‐2000 BP. The comparison between the model sea-level curve and the archaeological observations also enable to conclude that the average rate of vertical tectonic movement for the last 8000 years, at the Carmel coast, Israel, has been less than 0.2 mm/year. q 2001 Elsevier Science B.V. All rights reserved.

A LATE QUATERNARY PALEOENVIRONMENTAL SEQUENCE FROM DOR, CARMEL COASTAL PLAIN, ISRAEL

Abstract The 10.5 m deep “D-Dor” core was taken at Dor (Tantura Lagoon), on the Carmel coastal plain, Israel. The established chrono-stratigraphic sequence (based on x-ray radiographs, and both luminescence and radiocarbon dating) covers the last about 26,000 years. It provides the paleoenvironmental framework for the transition from hunter–gathering to agriculture in the Levant. Three clay units were identified, overlying kurkar (calcareous sandstone) and covered by 6.3 m of sand. The bottom clay unit is a paleosol. Pollen was not preserved in this unit. Gray clay (the top of which was dated to about 12,000 cal. YBP) was deposited, overlying the paleosol, in a wetland environment. Pollen was preserved only in the upper part of this unit. It indicates a slightly drier climate than todays, probably correlative with the Younger Dryas. At the beginning of the Holocene, between 10,300 and 9,550 cal. YBP, a new marsh originated, depositing dark clay. High concentrations of well-preserved pollen allowed the reconstruction of several fluctuations in humidity. When the marsh was first formed, precipitation was higher than today, and oak maquis was more extensive in the area. The date of the earliest submerged Pre-Pottery Neolithic settlement embedded in its upper part indicates that the marsh dried out no later than 9,400–8,550 cal. YBP. Around 5,000 years ago, long after the Early Holocene marsh had dried up, sand began to accumulate in the region as a consequence of the Holocene sea level rise, covering several submerged Neolithic settlements off the Carmel coast.

Holocene evolution of the Haifa Bay area, Israel, and its influence on ancient tell settlements

The geographical evolution of Haifa Bay and Zevulun Plain, Israel, from the late Pleistocene to the Holocene, is based on detailed analysis of drilled cores. At the beginning of the Holocene the Bay area was still under terrestrial conditions. Only about 9500 to 9000 cal. yr BP, when sea level rose to about 35-30 m below present sea level (b.s.l.), did Nile-derived sand start to bypass the Carmel headland and Haifa Bay come into existence as a morphological feature. Between 8000 and 7150 cal. yr BP, when sea level was 14-10 m b.s.l., the invading sea crossed the present-day coastline. At about 6800 to 6600 cal. yr BP sea level rose to about 5 m b.s.l. and flooded the Zevulun Plain up to 2 km inland, and the River Qishon estuary up to 4 km inland. It is still unknown exactly when the sea reached its maximum penetration inland but later, about 4000 years ago, the coastline in the research area was still east of the present-day coast, up to 3 km in the Zevulun Plain and 4.8 km in the River Qishon estuary. When the coastline started to retreat westward, the reclamation was followed by intensive deposition of shallow marine sand and aeolian dunes, while to the east, different wetland conditions developed. The archaeological data indicate that during the Early Bronze Age I and Early Bronze Age II, dated to between 5600 and 4700 cal. yr BP, and even later, during the Middle Bronze Age II period, about 4600 to 3500 cal. yr BP, the coastline was still east of the present-day coast, but it never actually reached the bases of most of the tells, as has been suggested, except for Tel Akko and Tel Abu Hawam.

Timing of the last Mediterranean Sea Black Sea connection from isostatic models and regional sea-level data

Water levels in the Mediterranean and Black Seas since the Last Glacial Maximum have varied substantially across the region because of the influence of the melting of the last great ice sheets in redistributing ice and water over the Earths surface. This spatial variability is significant for discussions of the timing of water exchange between the Aegean and Black Sea, which reached ca. -10 m relative to present sea level at 12 ky calBP. In the absence of direct observational evidence, sea-level change at sill locations is predicted here using isostatic models that have been calibrated against observational data from other Mediterranean localities. If one assumes a depth of ~ -32 m for the Bosphorus sill, the Black Sea is predicted to have been reached by rising Mediterranean water between about 10.3 and 9.5 ky calBP. Alternatively, if the Bosphorus bedrock gorge at ~ -100 m depth is adopted as the sill, then the first Mediterranean influx over the shallower Dardanelles sill at ~ -80 m is predicted to have occurred between 15 and 13.7 ky calBP.

Late Holocene embayment infill and shoreline migration, Haifa Bay, Eastern Mediterranean

Porat, N., Sivan, D., and Zviely, D. 2008. Late Holocene embayment infill and shoreline migration, the Haifa Bay, Eastern Mediterranean. Isr. J. Earth Sci. 57: 21–31. In the early Holocene sea-level rise caused transgression into the Haifa Bay, as in many bays and river mouths in the Eastern Mediterranean basin. Approximately 4,000 yr ago the sea reached its maximum transgression in the Zevulun Valley Plain, the eastern and terrestrial part of Haifa Bay, and the area was subjected to shallow marine and coastal sedimentation. Later, the coastline migrated to the west and the shallow marine sands were covered by coastal dunes. Across the Zevulun Valley Plain the top of these marine sands is within ± 1 m of present-day sea level. To provide a temporal framework for the establishment of the current sea level and the deposition of the aeolian and marine sands, a borehole was drilled 1,700 m inland, at 7.75 m asl, and eight samples were dated by optically stimulated luminescence (OSL). Sandy sediments comprise the entire borehole length (14.5 m). The transition from coarser shallow marine and coastal sand with mollusk fragments to the overlying finer coastal dunes is at a borehole depth of 7.5 to 8 m (0 ± 0.25 m asl). Quartz single-aliquot OSL ages range from 2,400 ± 110 yr at 3.0 m borehole depth to 4,150 ± 170 yr at 11.2 m depth. The transition from coastal to aeolian deposits took place about 3,650 yr ago, implying that within 0.5–1 m, sea level was then similar to the modern level. The chronology of the two sandy phases of the Zevulun Valley Plain has enabled the tracking of the shifting coastlines since 4,000 yr. The ages also have a bearing on our understanding of human occupation in these coastal areas and provide a reliable index point for the local sea-level curve.

Two centuries of coastal change at Caesarea, Israel: natural processes vs. human intervention

The coast at Caesarea, Israel, has been inhabited almost continuously for the last 2,400 years, and the archeological sites are today a major international tourist attraction. Because the sites straddle the shoreline, they are subject to constant damage by wave action, and must therefore be frequently restored. In this paper, local shoreline migrations over the last 200 years are investigated with the aim of distinguishing between natural and man-made coastal changes. In order to assess these changes accurately, geomorphological and sedimentological data were examined based on detailed beach profile measurements, bathymetric surveys, and grain-size analyses. In addition, series of old aerial photographs, as well as historical topographic maps and nautical charts were consulted. The results show that shoreline changes can be grouped into two main time periods. During the first period from 1862 to 1949 before the expansion of modern settlements, the position of the shoreline changed irregularly by up to 30 m. In the second period from 1949 onward, numerous coastal structures have been erected, and various coastal modifications have been carried out. The evaluation of the data suggests that human interventions have had relatively little effect on the overall position of the shoreline, as displacements ranged only from 5 to 18 m. Thus, coastal changes at Caesarea are predominantly due to natural wave action reflected in the heterogeneous geomorphological and sedimentological characteristics of the shore. This contradicts the common assumption that human activities are always mainly responsible for large-scale shoreline modifications in the region. It is concluded that, in order to implement meaningful mitigating countermeasures, coastal archeological sites need to be individually assessed with respect to the dominant factors causing local coastal change.

Sea-Level Changes in the Mediterranean: Past, Present, and Future – A Review

The study of geological and historical sea-level changes constitutes an important aspect of climate change and global warming research. In addition to the imminent hazards resulting from the inundation of low-lying areas along coastal regions, the rise in sea level can also cause erosion of beaches, salt intrusion into freshwater aquifers, and other damage to the coastal environment. The utmost importance of current changes in sea level is attributed to its impact on diverse ecological systems in coastal regions (Klein et al., 2004).

The interplay between relative sea-level rise and sediment supply at the distal part of the Nile littoral cell

During Holocene sea-level rise, coastal areas became transitional environments as marine incursion covered the land. Changing conditions resulted in dynamic depositional environments that recorded the migration and stabilization of modern shorelines. These processes are viewed in the Zevulun Plain (Haifa Bay, Israel) record located in the northern edge of the Nile littoral cell. Sedimentological and palaeontological analyses combined with dating enabled the reconstruction of the Holocene chrono-stratigraphical frame. The results reveal an unconformity representing a long period of exposure and erosion during the last glacial. The interplay between relative sea-level rise and sediment supply was first set out by the deposition of alluvial sediments, evidence of the hydrological system reactivation and base level landward migration. Sea flooding of the Zevulun Plain started about 7.8 cal ka BP and the coastline was pushed eastward. Nile-driven sands transported by longshore currents formed dunes that blocked the rivers estuaries and led to wetlands formation. Peat accumulation is evident first in the north of the plain at 7.6–6.2 cal ka BP and later in the south at 6.5–5.5 cal ka BP. Both wetlands showed a change from fresh to brackish water environments at the end of their existence. Following the maximum sea-level rise and inland sea invasion at about 4 ka BP, alluvial sediments covered the plain and the coastline moved westward to its current position. This record serves as a model for the development of Mediterranean clastic coasts controlled by sea rise and infill processes.

An Early Islamic Inter-Settlement Agroecosystem in the Coastal Sand of the Yavneh Dunefield, Israel

ABSTRACT This study examines the remains of an agricultural complex found in the Yavneh coastal dunefield, central Israel. Known as a plot-and-berm agroecosystem, the complex consisted of earthworks in a crisscross pattern of sand berms and sunken agricultural plots that were used for groundwater harvesting. The plots, which provided easy access to the high groundwater table and the berms around them, are overlaid by a gray sand unit covered by pottery sherds and artifacts. This gray sand is more fertile than the underlying sand, suggesting refuse enrichment. Artifactual similarity of the finds to those of inland (Tel) Yavneh suggests that Yavneh was the main source for the refuse additive. Based on artifacts and OSL ages it seems that this agroecosystem was active during the 10th to early 12th centuries a.d. The agroecosystem demonstrates an early example of an Early Islamic agrotechnological attempt in marginal and sandy regions of the Mediterranean basin.