Description:
<p>The name and personality of Rhodes W. Fairbridge have been intimately associated for more than three decades with fundamental and pioneering discoveries concerning the worldwide Holocene rise of sea level, together with its oscillations, cause and consequences. Parallel investigations in the southern Baltic regions owe much to his leadership and encouragement, often expressed in practical form through field-trips organized by the INQUA and IGU commissions. The southern Baltic shores and estuarine embayments ("Bodden") are quite different from most of the rocky coasts of Scandinavia in that they are essentially built of unconsolidated Quaternary sediments occupying an intermediate position between the "Förden" (drowned estuaries) of Schleswig and the "Haff-Nehrungen" (barrier spit/lagoon) coast of the southeastern Baltic in Poland. It is marked by a unique type of coastal geomorphology, exposed to storms of considerable fetch from north, west and east. Its features have been created over the last 10,000 years by a combination of wave action and rising sea level working on the arcuate moraines of the retreating Fennoscandian ice margin, together with some isolated cliffs of Cretaceous Chalk on the island of Rügen (Figure 1). Holocene sediments are 15–20 m thick and locally even more. Their alternating facies disclose definitive evidence of the fluctuating nature of the climate and sea level. The region is fortunate in possessing a very distinctive marker horizon near the very close of the Weichselian (latest Pleistocene) in the form of the Laachersee Tuff. This eruptive product came from a volcano in the Eifel district, south of Köln, leaving a layer a few mm thick in the Alleröd peat that overlies the glacial outwash and till of the Mecklenburg ice-retreat stage. The Alleröd was followed by the Younger Dryas, and eventually by the earliest Holocene (Preboreal) with its saline invasion; however, the sea level was much lower than today and these deposits did not reach the southern Baltic coast. Only in the later Preboreal (c. 9,000 BP, ¹⁴Cyr) did the rapidly freshening waters of the Ancylus stage reach the south coast of the Pommeranian Bight. Due to the isostatic tilting of Scandinavia, the initial seaway across central Sweden was closed, creating a giant lake, fingers of which have been traced in the estuarine belt between the Darss and the island Usedom (Figure 1). These estuaries mark the former glacial meltwater channels, which were occupied by the rise in water level. Isostatic tilting of Scandinavia, characterized by uplift to the north and sinking to the south led to a breakthrough of the rising North Sea at the Danish Belts, flooding the southern Baltic with saline waters. These eventually mixed with the fresh bodies of the Belt Lake and the Arkona Lake, but for nearly a thousand years (8,700–7,900 BP ¹⁴Cyr) there was a broad landbridge between Mecklenburg and the Danish islands, and the (Pre-) Pommeranian land area reached as far as the Oderbank. The breakthrough occurred about 7,900 BP initiating the first phase of the Littorina Sea, a fully marine condition when sea level rose an average of 0.9 cm/yr (Figure 2), at first reaching 2.5 cm/yr. By 5,700 BP it had almost reached present datum ("NN"). This rise in its absolute values and damped oscillations resembles the early versions of the globally-based Fair-bridge Curve (of 1958, 1960, 1961), although various interpretations are still appearing. With its extraordinarily rapid rise, the Littorina Sea invaded all the estuaries and bays of the southern Baltic. This transgression created an extensive archipelago of the former glacial landscape which was immediately involved in strong wave action. The region became populated by people of the Lietzow (Ertebölle-Ellerbek) culture, who were hunters, fishermen and gatherers, for whom the shallow estuaries provided an ideal habitat. Their artifacts are found, water-worn on the innermost beachridges, dating from around 5,500 BP. After the peak of Littorina, about 5,700 BP, there followed successive phases of the Littorina and post-Littorina periods, with oscillations slightly above and below present datum (cf Fairbridge curve). During these fluctuations extensive spit-building took place creating strandplains up to some km in width and extensive lagoons, some more or less cut off. Various stages of development are recognized. An alternation of beachridge and coastal dune building is observed, the beachridges reflecting episodes of extreme storm high-water. The dune series can be distinguished by the degree of podzolization of the inter-dune paleosols and by a color-gradation: brown, yellow, gray and white dunes. These distinctions are recognized likewise farther east in studies by Polish colleagues, which suggest that the brown dunes date from 4,810–1,403 BP (¹⁴Cyr). The yellow dunes are not older than 1,500 BP and are strikingly small, corresponding to the Medieval regressive phase. The gray dunes are marked by more dynamic activity and include numbers of migrating dunes, probably triggered by human agency, i.e., cattle grazing. The white dunes are simply their youngest manifestation. In a comparable way the spit-barrier building shows oscillatory pulses. Research by Schumacher (1990) suggests an alternation of meridional to zonal atmospheric circulation with a periodicity of 250–300 yr (avg. 275 yr) that marks at least the last 3,000 years, possibly even the whole Holocene; its last peak of maximum storm/high water was AD 1872. In conclusion, it should be pointed out that this southern Baltic coast represents a uniquely attractive and pristine landscape deserving of preservation and protection, to remain forever a region for study, and controlled tourism.</p>