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Sea-level changes of the Baltic Sea have been in the focus since the beginning of Baltic history studies. The main goal of the study is to reconstruct Holocene sea-level changes in the eastern part of Pomeranian Bay and the Szczecin Lagoon. For this purpose, 171 radiocarbon dates were used for the eastern part of Pomeranian Bay and 131 radiocarbon dates for the Szczecin Lagoon. The data allow reconstructing sea-level changes in the last 8500 years in the eastern part of Pomeranian Bay and 7500 years in the Szczecin Lagoon. The sea level 8500 yr b2k was ca. 16 m in Pomeranian Bay, while 7500 yr b2k in the Szczecin Lagoon, it was ca. 8 m below the present sea level. Initially, the fast sea-level rise (up to 9.0 mm/yr) slowed down about 6000 yr b2k to ca. 1.0 mm/yr. In the last 5000 years, the sea level rose at a rate of 0.5 mm/yr in both sites. Analysed data allow distinguishing an extreme event (or events) that disturbed a rather regular course of sea-level rise, which occurred between 7314 and 7022 yr b2k. The history of sea-level changes was similar in the eastern part of Pomeranian Bay and the Szczecin Lagoon despite differences in the geological structure of the pre-Quaternary bedrock and potential various trends in vertical crustal movements. Similarities to some other regions of the southern Baltic and the world ocean allow assuming that sea-level changes in the study area in the last 9000 years in general were eustatic in nature.

Coastal barriers are the first line of defense for the mainlands against the impacts of severe storms, therefore the need for better understanding how barriers evolve is arising. Spits (barriers) are the dominant landform type of the southern and south-eastern Baltic Sea coast. The aim of this paper is to gain present a better insight into problems of the Vistula Spit origin in general, and especially on the age of formation of the dune ridges. The Vistula Spit is one of the largest barriers on the southern Baltic coast. The analysis comprised: OSL dating of dune sands, radiocarbon dating of peat and palynological studies of peat and fossil soil profiles. Results shows that the onset of the oldest dunes formation begun ca. 7000–6000 years ago and the highest ridge were formed ca. 4000–2000 years ago. The youngest dunes, located closest to the modern shore, formed in the past 2000 years. Aeolian processes were also activated locally and periodically as a result of forest wildfires and human activities. Vistula Spit emergence and development is connected to two global events; beginning of the oldest dunes formation is related to slowing down in the sea level rise around 7000–6000 years ago, whereas the onset of the highest dunes building can be clearly connected with the climate cooling and aridification around 4200 years ago.

The climate variability and related sea-level changes during the Holocene are still under discussion, especially in a regional context. Very little information comes from the southern and south-eastern Baltic coast. The aim of the paper is to gain insight on the history of regional environmental changes, particularly sea-level and storminess, and their driving forces. The investigations were located on a peatland on the coast of Puck Lagoon (Gulf of Gdańsk, southern Baltic Sea). The analysis of peat core comprised: radiocarbon dating, analysis of stable isotopes 18O and 13C and chemical components, as well as palynological and diatomic studies. Results showed the 1.0 m peat section accumulated over 1500 years, with a time resolution of 100 years per sample. The average water level in the Puck Lagoon rose by ca. 0.85 m during the last 1500 years in a cyclic mode, with a period cycle of ca. 600–550 years and an amplitude not exceeding 0.5 m. The accelerated sea level rise and frequent storminess occurred during the first half of the Dark Ages (1500−1300 years b2k) and LIA (750−450 years b2k) and since the beginning of the 20th century. Recognized environmental changes are well correlated with both temperature changes in the North Atlantic and changes in total solar irradiance, suggesting synchronous Northern Hemisphere-wide fluctuations. The solar forcing was an important constituent of natural climate variability in the past and of forcing climate warming during modern times - after the Little Ice Age.

Coastal barriers account for approximately one-eighth of the world’s coastline. Barriers are the most common landform type in the southern part of the Baltic Sea area. Despite the long history of research, the issue of barrier coast evolution remains unresolved. The topic of this research is to determine the conditions under which the barrier coast evolved in the Holocene and to explain the local, different histories of its development. A 35 km long stretch of the coastal zone in the eastern Pomeranian Bay (southern Baltic) was explored using boreholes, seismoacoustic and GPR profiling, as well as radiocarbon and OSL dating, biostratigraphic studies and lithological analysis. Three main groups of deposits were identified: barrier subsoil deposits, barrier deposits (marine and aeolian sand, as well as interdune peat) and Rega River delta deposits. In the early Northgrippian (~8000 yr b2k), the coastline was located from about 2 to 12 km north of its present position. In the period 8000–6000 yr b2k, the coastline migrated southwards (landwards), initially at a rate of up to 22 m/yr and later up to 2 m/yr. The main driving forces at that time were climate warming and rapid sea level rise. When the Holocene transgression ceased, there were three different histories of the barrier coast development in the study area: a barrier that was still transgressive, a barrier that evolved from transgressive to progradational, and a barrier that evolved from transgressive trough progradational to transgressive again. The main determinants of these different histories were the lithology and relief of the barrier subsoil (accommodation space) and the time-varying amount of sand available for barrier formation, which varied in different parts of the study area.

Highlights: • A first standardized and publicly available Holocene relative sea-level database for the Baltic Sea is presented. • The database holds 1099 revised data points with an estimation of vertical and chronological uncertainties. • Negative RSL tendencies prevail over the positive and complex tendencies in the Baltic Sea Basin. • Mid-Holocene RSL highstand occurred around 7.5–6.5 ka BP being consistent with the end of the final melting of the LIS. • The contribution of ice loading in the eastern Baltic Sea Basin is likely overestimated in the ICE-5G and ICE-6G_C models. Abstract: We present a compilation and analysis of 1099 Holocene relative shore-level (RSL) indicators located around the Baltic Sea including 867 relative sea-level data points and 232 data points from the Ancylus Lake and the following transitional phase. The spatial distribution covers the Baltic Sea and near-coastal areas fairly well, but some gaps remain mainly in Sweden. RSL data follow the standardized HOLSEA format and, thus, are ready for spatially comprehensive applications in, e.g., glacial isostatic adjustment (GIA) modelling. We apply a SQL database system to store the nationally provided data sets in their individual form and to map the different input into the HOLSEA format as the information content of the individual data sets from the Baltic Sea area differs. About 80% of the RSL data is related to the last marine stage in Baltic Sea history after 8.5 ka BP (thousand years before present). These samples are grouped according to their dominant RSL tendencies into three clusters: regions with negative, positive and complex (transitional) RSL tendencies. Overall, regions with isostatic uplift driven negative tendencies dominate and show regression in the Baltic Sea basin during the last marine stage. Shifts from positive to negative tendencies in RSL data from transitional regions show a mid-Holocene highstand around 7.5–6.5 ka BP which is consistent with the end of the final melting of the Laurentide Ice Sheet. Comparisons of RSL data with GIA predictions including global ICE-5G and ICE-6G_C ice histories show good fit with RSL data from the regions with negative tendencies, whereas in the transitional areas in the eastern Baltic, predictions for the mid-Holocene clearly overestimate the RSL and fail to recover the mid-Holocene RSL highstand derived from the proxy reconstructions. These results motivate improvements of ice-sheet and Earth-structure models and show the potential and benefits of the new compilation for future studies.

A new chronology of the last Scandinavian Ice Sheet retreat in the southern Baltic basin is proposed. Based on Bayesian age modeling, we show that the most likely ages of particular deglaciation phases are 16.5 ± 0.5 ka for the Gardno Phase, 15.6 ± 0.6 ka for the Słupsk Bank Phase, and 13.9 ± 0.5 ka for the Southern Middle Bank Phase. The Gardno moraines are correlated with the Halland Coastal moraines in southern Sweden and the Middle Lithuanian moraines in Lithuania and Latvia. Ice margin stillstands of the Słupsk Bank Phase and Souhern Middle Bank Phase are correlated with the Göteborg and Vimmerby moraines, and with the North Lithuanian (Haanja) and Otepää moraines. The average retreat rates of the ice margin of about 55 m/yr between the Gardno Phase and the Słupsk Bank Phase, and about 40 m/yr between the Słupsk Bank Phase and the Southern Middle Bank Phase suggest that the last deglaciation did not accelerate after the Gardno Phase when an extensive ice-dammed lake was formed in front of the retreating ice sheet. The ice margin was probably grounded rather than floating, which prevented its more rapid retreat. The timing of the two main ice margin stillstands at the Słupsk Bank and at the Southern Middle Bank corresponds to the cool periods around 15 and 14 ka interpreted from paleotemperatures of Greenland based on ice core GISP2. This suggests that the main phases of the last deglaciation in the southern Baltic region were at least partly triggered by climatic fluctuations in the Northern Hemisphere.

PIERWIASTKI ZIEM RZADKICH W KONKRECJACH Fe-Mn Z POŁUDNIOWEGO BAŁTYKU – BADANIA WSTĘPNE Abstrakt. W latach 1976–1990 Panstwowy Instytut Geologiczny realizowal prace geologiczne na Polskich Obszarach Morskich. Oprobowano 7500 miejsc, a w 260 stwierdzono wystepowanie konkrecji. W roku 1980 prace kartograficzne prowadzono m.in. na obszarze progu oddzielającego Basen Bornholmski od Rynny Slupskiej, gdzie stwierdzono wystepowanie licznych konkrecji Fe-Mn. W niniejszym artykule są prezentowane wyniki analiz konkrecji pobranych na 4 stanowiskach. Badania dotyczą konkrecji nastepujących typow: dyskoidalnych D, nieregularnych I oraz przejściowych D-I. Badane konkrecje charakteryzują sie zmiennym skladem glownych tlenkow (Fe, Mn). Maksymalna zawartośc Fe2O3 wynosi 26,63%, a MnO 23,18%. Łączna średnia zawartośc REE + Y w badanych probkach jest na poziomie 165,11 ppm, ΣLREE – 145,72 ppm i ΣHREE – 19,39 ppm. Zauwazalne jest wzbogacenie w LREE w porownaniu do HREE. Konkrecje w wiekszości są zbudowane z tlenkow i wodorotlenkow Fe i Mn o bardzo niskim stopniu krystaliczności (praktycznie fazy mineralne są amorficzne). Glownymi potwierdzonymi fazami manganu są birnessyt i todorokit. Pozostalymi glownymi skladnikami konkrecji są: kwarc terygeniczny, albit, mikroklin, glaukonit i muskowit, klinochlor, mineraly ilaste: illit, chloryt. Wartośc tempa wzrostu w badanych konkrecjach, określona z uzyciem chronometru kobaltowego, wynosi od 0,006 do 0,134 mm/yr –1. Na podstawie zawartości Fe, Mn oraz (Cu + Co + Ni) badane konkrecje określono jako hydrogeniczne, podczas gdy uzywając zalezności REE (Cesn/Cesn · vs. Nd) jako diagenetyczne.

The remains of a Medieval harbour were discovered in Puck in 1977. Preliminary research was conducted the next year by Wieslaw Stepien. The site consists of a set of timber construction remains, located on the ground and strengthened with fascine, between which fragments of ceramics appear, especially in the area of the base of the pier. There are also a lot of pieces of simply processed trunks and branches stripped of bark nearby. Also, some scattered pieces of oak logs with yoke openings have been found lying distributed between the piles. Some help in attempting to reconstruct their arrangement comes from the mooring piles, which have a characteristic rectangular cross-section, and are still located on the sea bed. Pieces of five wrecks (one log boat, and four made from planks) have been found between the harbour constructions. Looking at the chronological arrangement of the site, created slowly on the basis of results obtained from dendrochronological analysis, and supplemented with radiological research, we can assume that the harbour was in use between the tenth and the 14th centuries. Key words: underwater archaeology, remains of Medieval harbour, sea level change, protection of cultural heritage, south Baltic, Puck Lagoon. DOI: http://dx.doi.org/10.15181/ab.v23i0.1310

The Baltic Sea is a semi-enclosed intracontinental sea of approximately 418 500 km 2 , surrounded by Scandinavia and the lowlands of Central and Eastern Europe. Its catchment area is about four times larger than the area of the sea itself. The Baltic Sea has an average depth of around 50 m, and is connected to the Atlantic Ocean via the shallow and narrow Danish Straits. A characteristic feature of the Baltic Sea is thermohaline stratification, in particular the occurrence of a permanent halocline. The northern part of the Baltic Sea is situated within the Precambrian Baltic Shield, whereas the southern part lies on the East European Platform. A small SW part lies on the Palaeozoic West European Platform. During the Pleistocene period, Scandinavian ice sheets advanced on the area of the present Baltic Sea several times, resulting in damage to the bedrock and a deepening of the Baltic Basin. The present-day Baltic Sea had its beginnings in the retreat of the last Scandinavian ice sheet, which melted approximately 15.5–14.5 ka ago in the area of the southern part of today's Baltic Sea. The Quaternary cover of the seabed in the area of the whole Baltic Sea is formed from Pleistocene sediments of glacial, glaciofluvial and limnoglacial origin, as well as from sediments of Holocene marine accumulation. In the southern part of the Baltic, during the Holocene, the sea constantly encroached upon the land, destroying Pleistocene sediments. In the northern part, as a result of uplift of the land and regression of the sea, Pleistocene glacial and glaciofluvial deposits, as well as early Holocene Baltic sediments, are being eroded. In the Baltic Sea, sandy and gravelly sediments are present above the pycnocline, while muds have been deposited below the pycnocline.

In this study, particulate organic carbon (POC) contents and their distribution pattern in surficial sediments of the Baltic Sea are presented for 1,471 sampling stations. POC contents range from approx. 0.1% in shallow sandy areas up to 16% in deep muddy basins (e.g. Gotland Basin). Some novel relationships were identified between sediment mass physical properties (dry bulk density (DBD), grain size) and POC levels. Notably, the highest POC concentrations (about 10–17 mg cm–3) occur in sandy mud to mud (60–100% mud content) with intermediate POC contents of about 3–7% and DBDs of 0.1–0.4 g cm–3. Areas with this range in values seem to represent the optimum conditions for POC accumulation in the Baltic Sea. The maximum POC contents (8–16%) are found in fluid mud of the central Baltic Sea characterized by extremely low DBDs (

The relative sea-level curve was developed for the southern Baltic area, based on a set of 315 radiocarbon dates of different terrestrial and marine sediments, collected at 164 sites located in the Polish part of the Southern Baltic and in the adjacent coastal land area. When developing the curve, relicts of various formations related to the shoreline evolution as well as extents of erosional surfaces, determined from seismoacoustic profiles, were taken into account. During the Late Pleistocene and Early Holocene, i.e., between 13.0 and 8.5 ka BP, the southern Baltic sea level rose and fell three times, the amplitude of changes extending over 25–27 m. In the Late Boreal, c . 8.5 ka BP, the Baltic—its water level by about 28 m lower than the present one—became permanently connected with the ocean. Until the onset of the Atlantic, the sea level had risen to about 21 m below present sea level. During 8.0–7.0 ka BP, the sea level was rising, to reach −10 m. Subsequently during the Atlantic, until its end, the sea level rose to 2.5 m b.s.l. During the first millenium of the Subboreal, the sea level rose to about 1.3–1.1 m b.s.l., to become—on termination of the Subboreal—about 0.7–0.6 m lower than present. During the Subatlantic, the sea-level changes were minor.

This chapter presents a newly discovered locality of tree stumps occurring in situ at the bottom of the Gulf of Gdansk. It focuses in particular on the age of the stumps and characterization of the palaeoenvironment, i.e. the nature of the plant communities in which the trees grew and also on their position in relation to the palaeo sea level. Tree stumps occurring in situ on the sea floor along with peat deposits are the most reliable indicators of sea level changes. The site is located about 6–7 km NE of the entrance to the Gdansk harbour, in water depth of 16–17 m. The thickness of marine sand at the site is from a few to a dozen centimetres. Below the sand, gyttja with peat intercalations and wood fragments occur. Sixteen fragments of alder trunks and one oak trunk’s fragment were extracted. Radiocarbon ages of the tree trunk fragments are 7,920 ± 50 BP, 7,940 ± 40 BP, 7,960 ± 40 BP and 8,000 ± 50 BP. The age of gyttja, according to pollen analyses, is of early Atlantic period. The characteristic forest composition of that time was the broad deciduous forest with oak (Quercus), elm (Ulmus) and lime (Tilia). The climate was characterized by good thermal and moisture conditions, which is confirmed by the presence of pollen grains of mistletoe (Viscum) and ivy (Hedera). The obtained data about the time of accumulation of the investigated sediments indicate that the sea level at that time was about 19–20 m lower than at present.

Investigations aimed at obtaining knowledge about the environmental effects of mining aggregate from the sea bottom were carried out on the Stupsk Bank. Special attention was given to the magnitude and reach of changes of hydrologic conditions, in that to changes in concentration of matter suspended in sea water, and to dynamics of the sea bottom—change of bottom relief, resulting from both natural causes and from mining of the aggregate.

The Vistula Lagoon is situated along the south-eastern shoreof the Gulf of Gdansk and is linked with the gulf through theStrait of Baltiysk. Separated from the open sea by the VistulaSpit, the Vistula Lagoon is a shallow body of water with a meandepth of 3 m; the bottom is covered with a layer of mud severalmetres thick.This article presents a unique, newly discovered localityof tree stumps occurring in situ at the bottom of the VistulaLagoon. The radiocarbon age of the alder stumps and the top ofthe peat in which they are rooted is Subboreal. The alder woodwas dated to 4770±35 and 3295±35 years BP. Thetop layers of peat were dated to 4670±40, 4410±35and 3690±35 years BP. The considerable scatter of thedates indicates the significance of erosional processes duringmarine transgressions. Radiocarbon dates and pollen analysesindicate that in the late Atlantic - early Subboreal periods,the water level of the Vistula Lagoon was about 3 m lower thanit is today. The -2 m level was passed no earlier than c. 3500years ago; the -1 m level was reached around 2000 years ago.