Fossil record of foraminifera and ostracoda from the Elsterian-Saalian-Interglacial in Schleswig-Holstein, Germany

Die in den Ablagerungen des marinen Elster-Saale-Interglazials (= Holstein-See = Stör-Meer) gefundenen und als autochthon betrachteten Foraminiferen und Ostrakoden kommen alle noch rezent vor. In vielen Proben wurden daneben aus dem Tertiär und der Oberkreide aufgearbeitete Foraminiferen gefunden. In den Proben aus Muldsberg, Albersdorf und Esbjerg konnte eine gleichgerichtete Faunen-veränderung vom Liegenden zum Hangenden beobachtet werden. Die Formen der jeweils unteren Proben gehören subarktischen bis hochborealen Temperaturen, etwa vollmarinem Milieu und mindestens 30 m Wassertiefe an. Ins Hangende hinein wurde nach Foraminiferen und Ostrakoden das Meer flacher, wärmer und brackischer, bis es schließlich in den obersten Proben wattähnliche Verhältnisse mit wahrscheinlich etwas geringerer Temperatur als am heutigen südlichen Nordseerand erreichte. Diese Beobachtung stimmt überein mit den von GRAHLE (1936) an Mollusken gewonnenen Erkenntnissen und den Schlüssen, die andere Bearbeiter aus einzelnen Mikrofaunen zogen. Es wurde versucht, die Faunen der restlichen Aufschlüsse in das oben erwähnte Schema einzuordnen. Dies gelang nur in zwei Fällen nicht. In Oldenhütten ist das Versagen wahrscheinlich auf unentwirrte Lagerungsstörungen zurückzuführen, in der Austernbank Tarbek liegen abweichende fazielle Verhältnisse vor. Die restlichen Aufschlüsse zeigen, daß aus den vom Eis gestörten Sedimenten doch oft ein sinnvolles Bild rekonstruiert werden kann. Die im kälteren Teil der Holstein-See auftretende Foraminifere Elphidium subarcticum CUSHMAN scheint in den Absätzen des schleswig-holsteinischen Eem-Meeres zu fehlen.

Geochemical analysis of sediments and interstitial water in sediment cores from the North-West African continental margin and from the Central Pacific

A. Continental slope sediments off Spanish-Sahara and Senegal contain up to 4% organic carbon and up to 0.4% total nitrogen. The highest concentrations were found in sediments from water depths between 1000 and 2000 m. The regional and vertical distribution of organic matter differs significantly. Off Spanish-Sahara the organic matter content of sediment deposited during glacial times (Wuerm, Late Riss) is high whereas sediments deposited during interglacial times (Recent, Eem) are low in organic matter. Opposite distribution was found in sediments off Senegal. The sediments contain 30 to 130 ppm of fixed nitrogen. In most sediments this corresponds to 2-8 % of the total nitrogen. Only in sediments deposited during interglacial times off Spanish-Sahara up to 20 % of the total nitrogen is contained as inorganically bound nitrogen. Positive correlations of the fixed nitrogen concentrations to the amounts of clay, alumina, and potassium suggest that it is primarily fixed to illites. The amino acid nitrogen and hexosamine nitrogen account for 17 to 26 % and 1.3 to 2.4 %, respectively of the total nitrogen content of the sediments. The concentrations vary between 200 and 850 ppm amino acid nitrogen and 20 to 70 ppm hexosamine nitrogen, both parallel the fluctiations of organic matter in the sediment. Fulvic acids, humic acids, and the total organic matter of the sediments may be clearly differentiated from one another and their amino acid and hexosamine contents and their amino acid composition: a) Fulvic acids contain only half as much amino acids as humic acids b) The molar amino acid/hexosamine ratios of the fulvic acids are half those of the humic acids and the total organic matter of the sediment c) The amino acid spectra of fulvic acids are characterized by an enrichment of aspartic acid, alanine, and methionine sulfoxide and a depletion of glycine, valine, isoleucine, leucine, tyrosine, phenylalanine, lysine, and arginine compared to the spectra of the humic acids and those of the total organic matter fraction of the sediment. d) The amino acid spectra of the humic acids and those of the total organic matter fraction of the sediments are about the same with the exception that arginine is clearly enriched in the total organic matter. In general, as indicated by the amino compounds humic acids resemble closer the total organic matter composition than the low molecular fulvic acids do. This supports the general idea that during the course of diagenesis in reducing sediments organic matter stabilizes from a fulvic-like structure to humic-like structure and finally to kerogen. The decomposition rates of single aminio acids differ significantly from one another. Generally amino acids which are preferentially contained in humic acids and the total organic matter fraction show a smaller loss with time than those preferably well documented in case of the basic amino acids lysine and arginine which- although thermally unstable- are the most stable amino acids in the sediments. A favoured incorporation of these compounds into high molecular substances as well as into clay minerals may explain their relatively high "stability" in the sediment. The nitrogen loss from the sediments due to the activity of sulphate-reducing bacteria amounts to 20-40 % of the total organic nitrogen now present. At least 40 % of the organic nitrogen which is liberated by sulphate-reducing bacteria can be explained ny decomposition of amino acids alone. B. Deep-sea sediments from the Central Pacific The deep-seas sediments contain 1 to 2 orders of magnitude less organic matter than the continental slope sediments off NW Africa, i.e. 0.04 to 0.3 % organic carbon. The fixed nitrogen content of the deep-sea sediments ranges from 60 to 270 ppm or from 20 to 45 % of the total nitrogen content. While ammonia is the prevailing inorganic nitrogen compound in anoxic pore waters, nitrate predominates in the oxic environment of the deep-sea sediments. Near the sediment/water interface interstital nitrate concentrations of around 30 µg-at. N/l were recorded. These generally increase with sediment depth by 10 to 15 µg-at. NO3- N/l. This suggests the presence of free oxygen and the activity of nitrifying bacteria in the interstitial waters. The ammonia content of the interstitial water of the oxic deep-sea sediments ranges from 2 to 60 µg-at. N/l and thus is several orders of magnitude less than in anoxic sediments. In contrast to recorded nitrate gradients towards the sediments/water interface, there are no ammonia concentration gradients. However, ammonia concentrations appear to be characteristic for certain regional areas. It is suggested that this regional differentiation is caused by ion exchange reactions involving potassium and ammonium ions rather than by different decomposition rates of organic matter. C. C/N ratios All estimated C/N ratios of surface sediments vary between 3 and 9 in the deep-sea and the continental margin, respectively. Whereas the C/N ratios generally increase with depth in the sediment cores off NW Africa they decrease in the deep-sea cores. The lowest values of around 1.3 were found in the deeper sections of the deep-sea cores, the highest of around 10 in the sediments off NW Africa. The wide range of the C/N ratios as well as their opposite behaviour with increasing sediment depth in both the deep-sea and continental margin sediment cores, can be attributed mainly to the combination of the following three factors: 1. Inorganic and organic substances bound within the latticed of clay minerals tend to decrease the C/N ratios. 2. Organic matter not protected by absorption on the clay minerals tends to increase C/N ratios 3. Diagenetic alteration of organic matter by micro-organisms tends to increase C/N ratios through preferential loss of nitrogen The diagenetic changes of the microbially decomposable organic matter results in both oxic and anoxic environments in a preferential loss of nitrogen and hence in higher C/N ratios of the organic fraction. This holds true for most of the continental margin sediments off NW Africa which contain relatively high amounts of organic matter so that factors 2 and 3 predominate there. The relative low C/N ratios of the sediments deposited during interglacial times off Spanish-Sahara, which are low in organic carbon, show the increasing influence of factor 1 - the nitrogen-rich organic substances bound to clay minerals. In the deep-sea sediments from the Central Pacific this factor completely predominates so that the C/N rations of the sediments approach that of the substance absorbed to clay minerals with decreasing organic matter content. In the deeper core sections the unprotected organic matter has been completely destroyed so that the C/N ratios of the total sediments eventually fall into the same range as those of the pure clay mineral fraction.

Pollen and macroremains from four profiles from site Samerberg 1

Pollen and macrofossil analysis of lake sediments revealed the complete development of vegetation from Riss late-glacial to early Würm glacial times at Samerberg (12°12' E, 47°45' N, 600 m a.s.l) on the northern border of the Alps. The pollen bearing sediments overlie three stratigraphic units, at the base a ground-moraine, then a 13 m thick layer of pollen free silt and clay, and then a younger moraine; all the sediments including the pollen bearing sediments, lie below the Würm moraine. The lake, which had developed in an older glacial basin, became extinct, when the ice of the river Inn glacier filled its basin during Würm full-glacial time at the latest. One interglacial, three interstadials, and the interdigitating treeless periods were identified at Samerberg. Whereas the cold periods cannot be distinguished from one another pollenanalytically, the interglacial and the two older interstadials have distinctive characteristics. A shrub phase with Juniperus initiated reforestation and was followed by a pine phase during the interglacial and each of the three interstadials. The further development of the interglacial vegetation proceeded with a phase when deciduous trees (mainly Quercus, oak) and hazel (Corylus) dominated, though spruce (Picea) was present at the same time in the area. A phase with abundant yew (Taxus) led to an apparently long lasting period with dominant spruce and fir (Abies) accompanied by some hornbeam (Carpinus). The vegetational development shows the main characteristics of the Riss/Würm interglacial, though certain differences in the vegetational development in the northern alpine foreland are obvious. These differences may result from the existence of an altitudinal zonation of the vegetation in the vicinity of the site and are the expression of its position at the border of the Alps. A greater age (e.g. the Holsteinian) can be excluded by reason of the vegetational development, and is also not indicated at first sight from the geological and stratigraphical data of the site. Characteristic of the Riss/Würm vegetational development in southern Germany - at least in the region between Lake Starnberg/Samerberg/Salzach - is the conspicuous yew phase. According to absolute pollen counts, yew not only displaced the deciduous species, but also displaced spruce preferentially, thus indicating climatic conditions less favourable for spruce, caused by mild winters (Ilex spreading!) and by short-term low precipitation, indicated by the reduced sedimentation rate. The oldest interstadials is bipartite, as due to the climatic deterioration the early vegetational development, culminating in a spruce phase, had been interrupted by another expansion of pine. A younger spruce-dominated period with fir and perhaps also with hornbeam and beech (Fagus) followed. An identical climatic development has been reported from other European sites with long pollen sequences (see chapter 6.7). However, different tree species are found in the same time intervals in Middle Europe during Early Würm times. Sediments of the last interglacial (Eem or Riss/Würm) have been found in all cases below the sediments of the bipartite interstadial, and in addition one more interstadial occurs in the overlying sediments. This proves that Eem and Riss/Würm of the north-european plain resp. of the alpine foreland are contemporaneous interglacials although this has been questioned by some authors. The climax vegetation of the second interstadial was a spruce forest without fir and without more demanding deciduous tree species. The vegetational development of the third interstadial is recorded fragmentary only. But it has been established that a spruce forest was present. The oldest interstadial must correspond to the danish Brørup interstadial as it is expressed in northern Germany, the second one to the Odderade interstadial. A third Early Würm interstadial, preserved fragmentarily at Samerberg, is known from other sites. The dutch Amersfoort interstadial most likely is the equivalent to the older part of the bipartite danish Brørup interstadial.