A high-resolution diatom-based Middle and Late Holocene environmental history of the Little Belt region, Baltic Sea

The large‐scale shifts in the salinity of the Baltic Sea over the Holocene are well understood and have been comprehensively documented using sedimentary proxy records. More recent work has focused on understanding how past salinity fluctuations have affected other ecological parameters (e.g. primary productivity, nutrient content) of the Baltic basin, and salinity changes over key events and over short time scales are still not well understood. The International Ocean Drilling Program Expedition 347 cored the Baltic basin in order to collect basin‐wide environmental records through a glacial–interglacial cycle. Site M0059 is located in the Little Belt between the Baltic Sea and the Atlantic Ocean. A composite splice section from Site M0059 was analysed at a decadal resolution to study changes in salinity, nutrient conditions and other surface water column parameters based on changes in diatom assemblages and on quantitative diatom‐based salinity inferences. A mesotrophic slightly brackish assemblage is seen in the lowermost analysed depths, corresponding to 7800–7500 cal. a BP . An increase in salinity and nutrient content of the water column leads into a meso‐eutrophic brackish phase. The observed salinity increase is rapid, lasting from 7500 to 7150 cal. a BP . Subsequently, the Little Belt becomes oligotrophic and is dominated by tychopelagic diatoms from c . 7100 to c . 3900 cal. a BP . This interval contains some of the highest salinities observed followed by diatom assemblages similar to those of the Northern Atlantic Ocean, composed primarily of cosmopolitan open ocean marine diatoms. A return to tychopelagic productivity is seen from 3850 to 980 cal. a BP . Anthropogenic eutrophication is detected in the last 300 years of the record, which intensifies in the uppermost sediments. These results represent the first decadally resolved record in the region and provide new insight into the transition to a brackish basin and subsequent ecological development.The large-scale shifts in the salinity of the Baltic Sea over the Holocene are well understood and have been comprehensively documented using sedimentary proxy records. More recent work has focused on understanding how past salinity fluctuations have affected other ecological parameters (e.g. primary productivity, nutrient content) of the Baltic basin, and salinity changes over key events and over short time scales are still not well understood. The International Ocean Drilling Program Expedition 347 cored the Baltic basin in order to collect basin-wide environmental records through a glacial-interglacial cycle. Site M0059 is located in the Little Belt between the Baltic Sea and the Atlantic Ocean. A composite splice section from Site M0059 was analysed at a decadal resolution to study changes in salinity, nutrient conditions and other surface water column parameters based on changes in diatom assemblages and on quantitative diatom-based salinity inferences. A mesotrophic slightly brackish assemblage is seen in the lowermost analysed depths, corresponding to 7800-7500 cal. a BP. An increase in salinity and nutrient content of the water column leads into a meso-eutrophic brackish phase. The observed salinity increase is rapid, lasting from 7500 to 7150 cal. a BP. Subsequently, the Little Belt becomes oligotrophic and is dominated by tychopelagic diatoms from c. 7100 to c. 3900 cal. a BP. This interval contains some of the highest salinities observed followed by diatom assemblages similar to those of the Northern Atlantic Ocean, composed primarily of cosmopolitan open oceanmarine diatoms. A return to tychopelagic productivity is seen from 3850 to 980 cal. a BP. Anthropogenic eutrophication is detected in the last 300 years of the record, which intensifies in the uppermost sediments. These results represent the first decadally resolved record in the region and provide new insight into the transition to a brackish basin and subsequent ecological development.Peer reviewe

New results of studies on the fossils in the Lower Cambrian sediment deposit of the Söderfjärden

Fossils Mickwitzia monilifera and olenellid trilobite fragments are found in the greenish grey shale in the lower sediment formation of Söderfjärden at a depth of 237.8 and 278.05 m. Microfossils (acritarchs) Archaeodiscina umbonulata, Baltisphaeridium cerinium, Granomarginata squamacea, Lophosphaeridium tentativum, Tasmanites bobrowskii, T. piritaensis were also observed in the lower part of the Söderfjärden sedimentary formation. In this lower intersection the microfossil genera resemble those in the upper sediment formation. Only one new species, Dictyotidium bottnicum, is described in the lower portion of the formation

Microfossils in a specimen of Cambrian (?) sandstone from Karstula, Central Finland

Fragments of sandstone, believed to be of Cambrian age, occur in the Pleistocene glacial drift at Karstula. The microfossils contained in one pebble were analysed under the microscope and with the aid of scanning electronmicrographs. Four types were defined. They possibly represent blue-green algae and fungi. The tentative dating of the sandstone could not be confirmed, but the results seem to suggest a late Precambrian age

Über Finnlands rezente und subfossile Diatomeen II

The article deals with the distribution and ecology of the Cyclotella, Stephanodiscus, Coscinodiscus, Actinoptychys, Auliscus, Actinocyclus, Rhizosolenia, Chaetoceros, Attheya and Terpisnoe species known in Finland

Über Finnlands rezente und subfossile Diatomeen VII

The article deals with the distribution and ecology of the Rhoicosphaenia, Diatomella, Mastogloia, Diploneis, Amphipleura, Frustulia, Brebissonia, Anomoeoneis and Stauroneis species known in Finland

Über Finnlands rezente und subfossile Diatomeen III

The article deals with the distribution and ecology of the Tetracyclus, Rhabdonema, Tabellaria, Grammatophora, Licmophora, Meridion, Diatoma, Plagiogramma, Dimerogramma and Opephora species known in Finland

Observations on the Quaternary geology of an area between the 2nd Salpausselkä and the ice-marginal formation of central Finland

The present study deals with the Quaternary formations and especially with the drumlins in the area between the Salpausselkä system in eastern Finland and the marginal formation of central Finland (Jyväskylä). Early late-glacial sediments from the area have been dated by C14 and pollen analyses. The Pieksämäki—Juva region is strongly drumlinized. According to seismic refraction data, the average thickness of the till forming a drumlin in Pieksämäki is about 20 meters. The drumlins in Joroinen are mostly low and narrow. According to seismic data, the till is also much thinner, averaging only 7 meters. The drumlins in the study area were formed, according to the authors, at a very late stage of the glaciation in the wide marginal region of a thinning glacier terminating in fairly shallow water. The weak glaciofluvial activity of the glacier could also have been a factor contributing to that formation, although in the final stage, it has been a question of the reactivation of the ice-flow. The most important of the presented sediment profiles from bogs is the stratigraphic section from the Vuorilampi-pond in Jyväskylä. It is located west of the proximal part of the marginal formation. The C14-age of the oldest dateable sediments from this area was 8 130 ± 160 B.C. According to pollen statistics, it corresponds to the beginning of the Preboreal or the end of the Younger Dryas period. Due to the possibility of having interglacial organic matter in the sample, the validity of the dating should be accepted with some reservation. It is, however, supported by the C14-dating made by Salmi (1962) from the oldest organic sediments of the Lapaneva bog in Kihniö, west of Jyväskylä

Über Finnlands rezente und subfossile Diatomeen IV

The article deals with the distribution and ecology of the Fragilaria, Ceratoneis and Synedra species known in Finland

Fossil bacterial forms in Early Proterozoic dolomite at Kiihtelysvaara in eastern Finland

The study deals with the bacterial type discovered in a Jatulian deposit at Kiihtelysvaara. The morphology of the microbic fossil, when compared with current forms, suggests that it is an early sulphur bacterium, named Hyypiana jatulica. The deposit is part of the Marine Jatulian dated at c. 2000 Ma. The fossile type occurs in chert nodules within the dolomite

Fossiliferous boulders of Lower Cambrian phosphoritic sandstone in southwestern Finland

The paper deals with fossiliferous sandstone boulders from three localities in southwestern Finland. The largest of the boulders was found on the west coast west of Olkiluoto. It is conglomeratic with an abundance of worn remains of lingulid and obolellid brachiopod valves. Its rock type is made up of a relatively coarse, bimodal quartz sandstone containing a few phosphoritic siltstone fragments. The main part is sandy and practically free of glauconite, which is more common in the phosphoritic fragments. A few of the phosphoritic pieces are tubular in form having phosphorite enriched in an outer ring and a one-grain-thick outermost crust of quartz. They may be worn remains of Hyolithellus micans. Some of the brachiopod shells contain small calcitic globules in a carbonaceous phosphorite matrix. Tasmanites sp. is one of the few preserved forms of the Acritarch genera. According to the fossils, the sandstone dates to the upper part of the Lower Cambrian, corresponding to the Lingulid sandstone facies in Västergötland, which in turn corresponds to the Holmia kjerulfi-group Zone in southern Scandinavia. Mineralogically and petrologically, too, the rock could be derived from such lithostratigraphical units. Sandstones of the same age have not been reported previously from Finland. The present boulders would seem to derive from the bottom of the Bothnian Sea. Although smaller and not so conglomeratic the boulders from Säkylä and Uusikaupunki are fossiliferous. The fossil fragments in the boulder from Pyhäjärvi, Säkylä, are probably remains of the brachiopod Mickwitzia, and thus refer to a Lower Cambrian stratum still older than the former. The worn brachiopod fragments in the boulder from North Viisastenkari, Uusikaupunki, did not allow the boulder to be dated more accurately within the Lower Cambrian