A palaeogeographic and geoarchaeologic study on the Colchian plain along the Black Sea coast of Georgia

The Colchian plain forms the central part of the Georgian coast. Due to its protected area between the ridges of the Greater and Lesser Caucasus and the resulting mild climate it constitutes a refugee area for thermopile species during the last glacial maximum (LGM) as well as an ideal location for early human occupation. Despite the existence of excellent geobio-archives, the number of geoarchaeological and palaeogeographical studies in the Black Sea area in general, and in Georgia in particular is – compared to e.g. the Mediter-ranean – rather small. Therefore, this study shall (i) decipher Mid- to Late Holocene land-scape changes, with special attention given to (ii) the Holocene relative sea-level (RSL) rise. In the context of the Black Sea-level history it is of special interest (iii) whether the water level rose oscillating or continuously. Furthermore, (iv) the geoarchaeological inves-tigations on settlement mounds shall clarify the influence of those landscape changing pro-cesses on human occupation of that region and (v) establish a chronostratigraphy that eventually verifies the mounds' Bronze age origin. This study is based on sediment cores that were gained from different locations on the Colchian plain between the rivers Enguri and Supsa. By using sedimentological and geo-chemical analyses (e.g., XRF and XRD-scans, LOI measurements, laser particle analyser etc.), sediment facies shifts in the natural depositional patterns and anthropogenic influ-ence could be determined. Age estimations were established by using AMS-radiocarbon and luminescence (IRSL) dating and rendered a chronostratigraphy. Consequently, an extensive landscape change in the research area was proven for the last 8000 years. While the coastline stayed more or less stable due to the extensive long-shore drift, its hinterland was turned through enduring sediment infill from an open lagoon into an alluvial floodplain since 3500 cal BC. Meanwhile the RSL rose continuously from -10 m below its modern level until it reached ~-2 m between 3000 and 1000 cal BC: Sub-sequently, the rise decelerated until it reached its modern level. These processes contra-dict the theory of an oscillating RSL rise, as proposed i.e. in the Balabanov-curve for the Georgian coast. They endorse instead the model of a continuous RSL evolution of the Black Sea. The investigated settlement mounds exemplify human occupation since at least the early 2nd millennium BC and verify archaeology-based implications of their Bronze Age origin. The stratigraphy of the settlement mounds hints rather an intentional accumulation of sed-iment layers than a succession of settlement layers as known from tells. The warm and humid climate that prevailed during their occupation and their environs that were dominat-ed by extensive wetlands back that assumption and exemplify the dependence and need for adaption strategies of human settlement to their surroundings. It was the first time, that a combination of sedimentological, geochemical and dating ap-proaches gained further knowledge on the landscape evolution of the Colchian plain and the relative sea-level evolution and gave first insights into human settling in complex envi-ronmental conditions

The Bronze Age occupation of the Black Sea coast of Georgia—New insights from settlement mounds of the Colchian plain

Along the lower course of the Rioni and several minor rivers, more than 70 settlement mounds (local name: Dikhagudzuba) have been identified by field surveys and remote sensing techniques. They give evidence of a formerly densely populated landscape in the coastal lowlands on the Colchian plain (western Georgia) and have been dated to the Bronze Age. As yet, limited information is available on their internal architecture, the chronology of the different layers and their palaeoenvironmental context. Based on archaeological sources, remote sensing measurements of three mounds and sediment cores from one mound and its closer surroundings, our study presents a review of the relevant literature and reveals the internal structure, distribution and spatial extent of the mounds. Geochemical and sedimentological analyses of element contents (X‐ray fluorescence) and granulometry helped to identify different stratigraphical layers and differentiate between natural facies and anthropogenic deposits; using the Structure‐from‐Motion technique the mounds' dimensions were calculated. The studied settlement mounds had relatively small dimension (varying from 30 to 100 m in diameter) and were similar in their stratigraphy. Measurement of elements that can identify types of human activity, notably metals and phosphorus, suggest changing intensities of human occupation, pastoral agriculture and metalworking through the occupation sequence. According to the 14C chronology, the formation of the settlements occurred during the first half of the second millennium B.C., which confirms the archaeological interpretation of their Bronze Age origin. The narrow age difference between the lowermost and uppermost anthropogenic layers indicates an intentional construction of the mounds, rather than a successive accumulation of construction debris due to the disintegration of loam bricks by weathering. Therefore, they are indeed mounds and not tells. It is most likely that the characteristic circular moats that surround them were the source of their construction material. Fluvial and alluvial processes in a warm and humid climate dominated the environment of the mounds

Dimaprit analogues inhibit tyrosinase via a disulphide breakdown product independently of the histamine (H2) receptor.

Histamine displayed specific and saturable binding to membrane fractions of the human melanoma cell line MM96E (Kd = 72.4 nM and Bmax = 487 fmol/mg protein). There was weak competition with isothioureas that inhibit tyrosinase in intact cells: dimaprit (an H2 agonist) nordimaprit and S-[2-(N,N-diisopropyl)ethyl] isothiourea (DINOR). Under culture conditions, rapid, pH-dependent hydrolysis of the isothiureas occurred, with cleavage to urea and a thiol which spontaneously oxidised to the disulphide. The H3 agonist imetit, which also inhibited tyrosinase, behaved similarly. The disulphide breakdown product of DINOR but not the thiol inhibited tyrosinase activity in intact MM96E cells to a similar extent as DINOR itself. Isothioureas with more bulky substituents, however, were stable in culture and did not inhibit tyrosinase. The results show that (a) certain histaminergic drugs exert effects via a disulphide hydrolysis product independently of the histamine H2 receptor, and (b) ߭aminoethyldisulphides are depigmenting agents.No Full Tex