Marine Interglacial Deposits in the Cuxhaven Area , NW Germany : A Comparison of Holsteinian , Eemian and Holocene Foraminiferal Faunas

Interglacial foraminiferal faunas are described from Holsteinian, Eemian, and Holocene deposits in borings from the Cuxhaven area. These assemblages are compared with published faunal lists from corresponding interglacial deposits in NW Germany and Denmark. The faunal succession of each interglacial sequence in the ptesent area has its own characteristic featutes. Of particular interest is the fact that the ptesence and/or abundance of certain taxa in each of the interglacials may prove to be use­ ful for correlation purposes in the southern North Sea area. [Marine Interglazialablagerungen aus dem Raum Cuxhaven, NW-Deutschland: Ein Vergleich der Foraminiferen-Faunen von Holstein, Eem und Holozän] Kurzfassung: Es werden interglaziale ForaminiferenFaunen aus dem Holstein, dem Eem und dem Holozän für den Raum Cuxhaven beschrieben. Bei den bearbeiteten Pro­ ben handelt es sich um Marerial aus Kernbohrungen. Die Vergesellschaftungen werden mit vorliegenden Publikatio­ nen entsprechender Vorkommen aus Nordwestdeutschland und Dänemark verglichen. Jede der 3 untersuchten Faunen hat typische Züge. Von besonderem Interesse ist die Tatsache, daß die Anwesenheit und/odet Häufigkeit bestimmter Taxa für das Gebiet der südlichen Nordsee stratigraphische Korrelationen ermög­ licht.


Introduction
This paper describes and compares the foraminiferal faunas of marine Holsteinian, Eemian, and Holocene deposits in the Cuxhaven area, NW Germany.Results of the Holsteinian of the Neuwerk borings (figs. 1 and 2) have already been published (KNUDSEN 1988a).*) Authors address: Dr. K. L. KNUDSEN, Geologisk Insti tut, Aarhus Universitet, DK -8000 Arhus C, Denmark.
The samples examined in the present study have been treated according to the laboratory methods described by MELDGAARD & KNUDSEN (1979)

Foraminiferal zonation and palaeoenvironment
The marine inrerglacial sequence has been subdivided into 3 foraminiferal assemblage zones, zones L1 to L3.The relative frequencies of the most common taxa in each sample is shown in the range chart, fig. 4.
Only one sample (18.75-19.00m depth) is included in the lowermost zone LI.Elphidium albiumbilicatum is the dominant species, and Nomon orbiculare, Buccella frigida, Elphidium incertum, E. williamsoni, and Nonion germanicum also occur.The sediment is rich in plant debris, and the foraminiferal tests are partly secondarily dissolved, probably by acidic ground water.The high frequency of E. albiumbilicatum in zone LI points to an initial stage of a marine transgression (see also PENNEY 1985, fig. 3).According to LUTZE (1965) this species can tolerate extremely low salinities.Most of the species in zone L1 are the same as found in intertidal areas of the boreal faunal province today (i.a. VAN VOORTHUYSEN I960;HAAKE 1962).
Assemblage zone L2 covers the interval from 18.75 to 16.50 m.The sharp rise in Elphidium incertum and Buccella frigida indicates a rapid change to deeper, sublittoral conditions and higher salinities.Other characteristic faunal elements include Elphidium williamsoni, Nonion niveum, and N. orbiculare.E. albiumbilicatum still occurs, together with low frequencies of Ammonia batavus.These faunas indicate temperate climatic conditions.The water depth may have been as much as 10-20 m.The rise in Ammonia batavus at the top of the zone L 2 is an indication of a return to shallower, intertidal conditions.Ammonia batavus dominates zone L3, but Nonion germanicum and Elphidium albiumbilicatum are still common species.This faunal composition, together with the marked rise in Elphidium gunteri, indicates extremely shallow water and reduced salinities (see also UFFENORDE 1982).
The complete Eemian marine transgression is, thus, preserved at Lüdingworth.Marine conditions were first established above a peat horizon at about 19 m depth (zone Ll).The environment was initially brackish and shallow, but was rapidly superceded by a period with more saline, sublittoral conditions (zone L2).The final stage (zone L3) records a return to shallow, brackish waters consequent on a fall in sealevel.
Common to the Eemian faunas in the above-mentioned studies is the presence of Nonion niveum.This species is especially characteristic for Eemian faunas in the eastern part of the region, i. e. from the Oldenbüttel area and eastwatds to the areas around the Baltic Sea (see also KNUDSEN 1985).The two lusitanian  (1964).Legend in fig. 5.
Pollen investigations of eight samples from the interglacial sediments at Lüdingworth were made by R. HALLIK and kindly placed at my disposal.His results confirm that the deposits are Eemian in age.A correlation between the foraminiferal zones and the pollen results is shown in fig.6. Eemian pollen zones are here used in accordance with SELLE (1962) (see also MÜLLER 1974).The deepest pollen sample is from a level just below the first marine zone (no.8 at 19-00-19 05 m depth).This was placed at the pollen zone I/II boundary, corresponding to the Betula Mil Pinus rise.
Pollen zones II and Ilia are lacking due to transgressional erosion.A sample at the base of the marine sequence (sample no. 7, foraminiferal zone LI, fig. 6) corresponds to the zone III a/III b boundary according to HALLIK, while the top sample from the marine sequence can be placed within the upper part of pollen zone IVb, i. e. towards the end of the Carpinus maximum.The pollen and foraminifera, thus, complement each other, as both indicate that the marine deposition was restricted to the true interglacial period.

The Neuwerk borings
Holsteinian foraminiferal faunas from borings at Neuwerk have been described in detail by KNUDSEN (1988 a).The Holocene sediments from the same area were investigated by LINKE in 1970, but their foraminiferal faunas have not previously been described.
The foraminiferal succession through the Holocene sequence is, thus, presented below for one of these borings (6/77), together with Holsteinian assemblages from a neighbouring boring (6/74, figs. 2 and 7).

The Holsteinian of Neuwerk 6/74
The marine sequence berween 29.0 and 45.2 m depth in this boring has been referred to the Holsteinian Interglacial on the basis of both pollen and foraminifera (LINKE et al. 1985;KNUDSEN 1988a).
The faunal compositions in the assemblage zones EA, EW, and EN indicate a gradual change from a very shallow, intertidal habitat in the lower zone to slightly deeper, more open conditions in the top zone (see also KNUDSEN 1988 a).Of a special interest is the co occurrence of arctic taxa, such as Elphidium hallandense and Nonion orbiculare, with the lusitanian Aubignyna perlucida.Pollen analyses of the Holstei nian deposits from the Neuwerk area show that these marine sediments were deposited during the pollen zone 3 after LINKE & HALLIK (prel.comm.1986, Inqua-Symposium: Holstein-Interglazial, Hamburg).This corresponds the pollen zone 3 of ERD (1973) and pollen zones VII/VIII of MÜLLER (1974).
The Holsteinian foraminiferal faunas correspond to those found in similar deposits in the adjacent areas of NW Germany, and especially those that indicate relatively direct access to normal marine North Sea waters in Schleswig-Holstein and at Hamburg (KNUD SEN 1988 b).Abb.6: Korrelation der Eem-Foraminiferen-Zonen bei Lüdingworth mit den Pollen-Zonen nach MÜLLER (1974).

The Holocene of
The marine Holsteinian deposits at Neuwerk are typi cally overlain by a 5-10 m thick sequence of glaci genic sediments (fig.8), which are considered Saalian in age (LINKE 1970).This unit is overlain by marine Holocene silts and sands, at some places with a basal peat at the bottom.Holocene sediments here have a maximum thickness of about 25 m.
The marine Holocene of boring 6/77 is subdivided into two foraminiferal zones, zones HI and H2.Each sample in this sequence spans an interval of 1 m of sediment.
Zone HI is dominated by Ammonia batavus and Elphidium williamsoni, but Nonion germanicum, N. depressulum, Elphidium excavatum forma selseyensis (see FEYLING-HANSSEN 1972), E. gunteri, and E. magellanicum are also common species.The relative importance of Elphidium gunteri, together with low numbers of E. albiumbilicatum points to the presence of a shallow, brackish intertidal environment at the base of the sequence.The zone HI fauna may, how ever, well represent two different types of envi ronment.This is indicated by the occurrence of low • - -5 -10 -5 • FAUNAL DIVERSITY numbers of several taxa that belong in shallow subtidal habitats in the North Sea today (see below).
The frequencies of Elphidium gunteri and E. albium bilicatum decrease in the zone H2 assemblages.The presence of many accessory species, such as Elphidium gerthi, E. voorthuyseni, E. margaritaceum, Nonion depressulum, Bolivina pseudoplicata, Quinqueloculina seminulum, etc. is a characteristic feature of the zone H2 faunas.This species composition seems to indicate more open conditions and maybe slightly deeper water than in zone H1.The assemblages correspond to those found in intertidal and shallow subtidal environments of the southern North Sea to day (HAAKE 1962;RICHTER 1967), and to Holocene faunas described by UEFENORDE (1982) andSORENSEN (1980) from borings in the southern North Sea area.
The faunal diversity indices range from 5 to 8 through the total Holocene sequence.This corresponds to the values in the upper part of the Holsteinian sediments of the same area (fig.7).The marked decrease in specimen numbers towards the top of the Holocene may be an indication of relatively higher accumulation rates here.No secondary etching of foraminiferal tests is observed.

Comparison of the interglacial foraminiferal faunas
A comparison of the Holsteinian and Holocene species composition in fig.7 shows that the two are almost equal.Certain different characteristics do, however, occur, which may be useful for correlation purposes.One of these is the presence of certain arctic taxa in the Holsteinian deposits at Neuwerk.Arctic species are especially common in the early part of the Holstei nian Interglacial in both NW Germany and SW Den mark.They have, for example, been recorded in the Holsteinian of Eggstedt and Dockenhuden (KNUDSEN 1988b), at Wacken (KNUDSEN 1988c), and at the base of the Holsteinian at Tornskov (KNUDSEN 1987 b).
The co-occurrence of Buccella frigida and Nonion orbiculare can also be considered a characteristic fea ture throughout the marine Holsteinian of NW Ger many and SW Denmark.
Another typical feature of the Holsteinian faunas in the southern North Sea area is the presence of the lusitanian species Aubignynaperlucida (see also KNUDSEN 1980KNUDSEN , 1987b)).This species occurs only sporadically both in the Holocene and in the Eemian Interglacial deposits in this region.It is normally much more common in the Holsteinian than was the case in the Neuwerk boring (fig.7).
Eemian Interglacial faunas can be distinguished from the Holsteinian and Holocene faunas by the co-occur rence of Buccella frigida, Nonion orbiculare, and Nonion niveum.These taxa are, for example, present in Eemian deposits at Lüdingworth (fig.4), and they have been recorded at many other Eemian sites in the southern North Sea region, e. g. at Oldenbüttel (KNUDSEN 1985) and Stohl (KUBISCH & SCHÖNFELD 1985) in Schleswig-Holstein and at T0nder (SORENSEN 1980) and Stensigmose (KONRADI 1976) in Denmark.
Quinqueloculina padana, another lusitanian species, is a characteristic element of deeper water Eemian de posits of N. Jutland, Denmark (KNUDSEN & LYKKE-ANDERSEN 1982;KNUDSEN 1984).This species is not found in Eemian intertidal deposits.Shallow subtidal and intertidal Eemian sediments may, however, be characterized by the presence of other lusitanian taxa, such as Quinqueloculina aspera and Q. seminulum var.jugosa.Both species requires normal marine sali nities, and they have, for instance, been recorded in Eemian faunas along the North Sea coasts of the Netherlands ( VAN VOORTHUYSEN 1957) and Denmark (SORENSEN 1980).The latter taxa was also found in the Eemian of the western part of Schleswig-Holstein (LAFRENZ 1963).
It is, therfore, normally possible to distinguish Eemian Interglacial faunas from other interglacial assemblages by their warmer water aspect.For un known reasons lusitanian species are almost absent in the Eemian assemblages at Lüdingworth (fig.4).

Foraminifera
The species mentioned in the text are arranged alpha betically in the following list.Only the most common occurrring species and those which have been signifi cant for the interpretation are mentioned here.
and KNUDSEN (1988 b).The percentage frequencies of the most com mon foraminiferal species are shown in range charts (figs.4 and 7).Assemblage zones have been estab lished in accordance with the definition given by HEDBERG (1976).