The "Lake of Olympia": geoarchaeological evidence of a lake environment in the vicinity of ancient Olympia (western Peloponnese, Greece)

Our results yield evidence of a large lake environment that existed near the ancient site of Olympia which was so far unknown. The limnic sequence reveals considerable changes in the ecological conditions over time, based on Direct Push sensing, sedimentary and micropalaeontological analyses. Radiocarbon data show that the “Lake of Olympia“ existed from the 8th/7th millennium BC until, at least, the 1st century AD. The existence of the “Lake of Olympia” next to the cult site of Olympia has considerable historical, archaeological and geographical implications (e.g., as waterway or water supplier)

A Previously Unknown Building Structure in Ancient Olympia (Western Peloponnese, Greece) Revealed by Geoarchaeological Investigations and Its Interpretation as a Possible Harbor

The ancient site of Olympia is located on the northern fringe of the Basin of Makrisia at the confluence of the Kladeos and Alpheios rivers (western Peloponnese, Greece) and was used as a venue for the Panhellenic Games from Archaic times until the 4th century AD. Geophysical prospection (frequency domain electromagnetic induction and electrical resistivity tomography) was carried out as a basis for detailed geoarchaeological investigations. In doing so, we identified a previously unknown building structure adjacent to the Altis, the inner part of the sanctuary at Olympia. Situated south of the Southwest Thermae, this structure measures at least 100 m (WSW-ENE) by 80 m (NNW-SSE). Its external orientation is in line with the orientation of the Southwest Thermae and the Leonidaion. We retrieved sediment cores from 17 different locations in combination with high-resolution direct push sensing from inside the newly found structure. All cores revealed distinct units of organic-rich limnic sediments dominated by clay and fine silt. Geochemical and micropaleontological analyses of selected sediment samples indicate highly eutrophic conditions, as evidenced by elevated phosphorous concentrations and the dominance of the ostracod species Cyprideis torosa, which is able to live under low-oxygen conditions. Moreover, molecular biomarker analyses show a significant input of lipid fecal markers, implying strong anthropogenic pollution. Further, the limnic sediments include numerous charcoal remains and abundant diagnostic artifacts such as ceramic fragments and building material. Radiocarbon dating documents that these limnic conditions persisted within the building structure from at least the 5th century BC to the 6th century AD. The identified building structure lies in the immediate proximity to the Lake of Olympia, which was recently found to have existed from the mid-Holocene to the Medieval period. Its characteristic filling with fine-grained sediments and multiple indications for a strongly polluted and heavily used standing water environment let us hypothesize that it was possibly used as a harbor installation. A harbor at ancient Olympia could have been used to reach the sanctuary by boat and to transport goods of all kinds

Possible Indication of the Impact of the Storegga Slide Tsunami on the German North Sea Coast around 8150 cal BP

The Storegga slide tsunami (SST) at ca. 8100 ± 100–250 cal BP is known to be the largest tsunami that affected the North Sea during the entire Holocene. Geological traces of tsunami landfall were discovered along the coasts of Norway, Scotland, England, Denmark, the Faroes and Shetland Islands. So far, the German North Sea coast has been considered as being well protected due to the wide continental shelf and predominant shallow water depths, both assumed to dissipate tsunami wave energy significantly, thus hindering SST propagation dynamics. The objective of our research was to clarify if the SST reached the German Bight and if corresponding sediment markers can be found. Our research was based on the in-depth investigation of a 5 m long section of the research core Garding-2 from Eiderstedt Peninsula near Garding in North Frisia known from a previous study. For this, we newly recovered sediment core Garding-2A at exactly the same coring location as core Garding-2. Additionally, high-resolution Direct Push sensing data were collected to gain undisturbed stratigraphic information. Multi-proxy analyses of sediment material (grain size, geochemical, geochronological and microfaunal data) were carried out to reconstruct palaeoenvironmental and palaeogeographical conditions. We identified a high-energy event layer with sedimentological (e.g., erosional unconformity, rip-up clasts, fining-upward), microfaunal (e.g., strongly mixed foraminiferal assemblage) and other features typical of tsunami influence and identical in age with the SST, dated to ca. 8.15 ka cal BP. The event layer was deposited at or maximum ca. 1–1.5 m below the local contemporary relative sea level and several tens of kilometers inland from the coastline within the palaeo-Eider estuarine system beyond the reach of storm surges. Tsunami facies and geochronological data correspond well with SST signatures identified on the nearby island of Rømø. SST candidate deposits identified at Garding represent the southernmost indications of this event in the southeastern North Sea. They give evidence, for the first time, of high-energy tsunami landfall along the German North Sea coast and tsunami impact related to the Storegga slide. SST deposits seem to have been subsequently reworked and redeposited over centuries until the site was affected by the Holocene marine transgression around 7 ka cal BP (7.3–6.5 ka cal BP). Moreover, the transgression initiated energetically and ecologically stable shallow marine conditions within an Eider-related tidal channel, lasting several millennia. It is suggested that the SST was not essentially weakened across the shallow continental shelf of the North Sea, but rather caused tsunami run-up of several meters (Rømø Island) or largely intruded estuarine systems tens of kilometers inland (North Frisia, this study). We, therefore, assume that the southern North Sea coast was generally affected by the SST but sedimentary signals have not yet been identified or have been misinterpreted. Our findings suggest that the German North Sea coast is not protected from tsunami events, as assumed so far, but that tsunamis are also a phenomenon in this region

The "Lake of Olympia": geoarchaeological evidence of a lake environment in the vicinity of ancient Olympia (western Peloponnese, Greece)

Our results yield evidence of a large lake environment that existed near the ancient site of Olympia which was so far unknown. The limnic sequence reveals considerable changes in the ecological conditions over time, based on Direct Push sensing, sedimentary and micropalaeontological analyses. Radiocarbon data show that the “Lake of Olympia“ existed from the 8th/7th millennium BC until, at least, the 1st century AD. The existence of the “Lake of Olympia” next to the cult site of Olympia has considerable historical, archaeological and geographical implications (e.g., as waterway or water supplier).</jats:p

The Lake of Olympia: Sedimentary evidence of a mid- to late Holocene lake environment in the vicinity of ancient Olympia (western Peloponnese, Greece)

Olympia (western Peloponnese, Greece) is known as venue for the Panhellenic Games in ancient times. The wider region is located within a complex tectonic setting and was affected by crustal uplift up to 30 m since the mid-Holocene.Our study consists of a comprehensive investigation of the Basin of Makrisia and the adjacent Basin of Ladiko in the vicinity of ancient Olympia aiming to reconstruct the Holocene landscape development. In addition to Direct Push measurements, we present stratigraphic data of 15 sediment cores. Multi-proxy analyses of selected sediment cores, including sedimentological, geochemical and ostracod studies, allow to detect and interpret alterations in the depositional processes.We found widespread fine-grained, low-energy sediments, implying distinct phases of limnic conditions. Radiocarbon dating indicate that this lake, the so-called Lake of Olympia, persisted from the 8th millennium BC at least until the 6th century AD, covering the main period of the cult site. Ancient Olympia was then located at the direct lake shore. The lake finally disappeared during the 13th/14th century, when the water level of the Alpheios River abruptly dropped by several meters to its present position, forming the Olympia Terrace.We identified different ecological lake phases ranging from freshwater to eutrophic conditions. During ancient times, the water quality in front of Olympia was characterized by strong, possibly man-made eutrophication. We reconstructed lake level changes since the 1st millennium BC, noting a continuous rise until around 600 AD followed by abrupt drops in the 13th/14th century AD. In ancient times, the water depth around Olympia was deepest south of the Southern Hall.The presence of a lake has significant consequences for the discharge regime and sediment transport of the Alpheios River and its tributaries. Also, the Lake of Olympia has relevant historical, archaeological, and geomorphological implications and raises several unsolved questions