Frühdiagenetische Karbonatzementation in glazigenen und fluviatilen Sedimenten des Wesertales NW Hameln

In the Weser valley NW Hameln early diagenetic carbonate cementation is present in the upper Elsterian to Drenthe sediments. Examination of the calcite cement indicated a multiphase formation. Cementation occured mainly in vadose environment above ground-water table. This process generated predominantly brown calcite cement with a crystal size of <5 to 20pm. Next to meniscus-cement this fine-crystalline calcite forms further cements typical for vadose zone. In one layer of the „Mittelterrasse'-sediments, deposited in the late Elsterian age, a calcite cement is present, which may already have formed in the Holstein Interglacial. Cementation started in the upper-most layers of the „Mittelterrasse'-sediments in a late phase of „Mittelterrasse“-accumulation in this area. The so formed consolidated layers were deformed by the Drentheglacier. After ice melting cementation continued in at least 3 phases, creating nonluminiscent phreatic, orange to red luminiscent vadose and nonluminiscent vadose calcite cement.

Oberjurassische Korallen-Geschiebe (Thamnasteria concinna) aus einer Kies-/Sandgrube bei Freden/Leine (Leinebergland)

Upper-Jurassic geschiebe-corals (Thamnasteria concinna) from a gravel-/sandpit at Freden/Leine are described. They are slightly bored by bivalves (Gastrochaenolites) and worms (Trypanites). Some oysters (Nanogyra Inana) encrusted the surface. The corals growed as massiv head-like (bulbous) colonies with "multicolumnar growth form" and ragged outlines. Similar shaped colonies are reported from Easteuropean Upper Jurassic (Pommerania), but are never reported for NW-Germany. Beds in which the coral-geschiebe were found - Drenthe stage in age - contain a high content of local geschiebe-material. The low degree of abrasion of the coral-geschiebe indicates short glacial transportation. It is possible, that the geschiebe originate from the Heersumer Schichten from Selter to Thüster Berg.

Elfas und Ahlsburg - die Struktur der Schollengrenze zwischen Hils und Solling

The Elfas, Ahlsburg, and Salzderhelden overthrusts have been considered for a long time to be halotectonic structures caused by diapiric rise of Zechstein salt into thrust planes and other zones of weakness in the overlying rocks. Much of the Markoldendorf syncline between the overthrusts is covered by Quaternary deposits. The structure of the syncline and its western and southern boundaries were mapped with the help of many boreholes and micropalaeontological dating during remapping of the 1 : 25 000 geological sheet 4124 (Dassel). The Ahlsburg overthrust has now been shown to continue to the NW and to lead into the Lüthorst graben, which truncates the syncline in the west and passes into the crestal fault of the Elfas anticline. Figure 6 shows the NW-SE trending faults bounding three blocks which, according to seismic interpretation (Geotectonic Atlas 1996), have moved several times, in some areas in opposite senses. The NNE-SSW-trending grabens act as hinges, separating the NW-SE faults into sections that have undergone different movement.

Geschiebekundlich-stratigraphische Untersuchungen in der südlichen Lüneburger Heide

An outline of the Pleistocene history of the southern Lüneburg Heide is given based on the interpretation of exposed sections and indicator-stone analysis. Locally, Elsterian sediments crop out at the surface, mainly near the Holsteinian kieselgur (diatomite), thus indicating the existence of a pre-Saalian relief. Most of the Pleistocene deposits were formed during the three Saali- an ice advances. The ground moraine (basal till) of the first advance (the main Drenthe moraine) and its outwash sands are only locally exposed and only at the margin of the Aller valley do they form a relatively extensive plain. To the north, they are overlain by outwash sands of the late Drenthe advance. Also the Uelzen end moraine consists mainly of these outwash sands. The Uelzen moraine was overridden by the same ice advance. The Warthe ice sheet left only minor traces ridge; its advance came to a final stop at the already dumped morainic material.

Oberjura-Riffe in NW-Deutschland : ein Überblick

For the first time, in this study NW-German coral and reef localities are comprised. Three well exposed and developed reefal units, which have been analyzed by a working group located at the Institut für Geologie und Paläontologie in Hannover, are extensively described and classified orientated with pre-existing reef classifications. The paleoecologic interpretation of these reefs is compared with several similar reefal units from throughout W and SW Europe.

Kies- / Sandkörper im Wesertal zwischen Rinteln und Porta Westfalica

In this article the sand-/gravelbodies from Hausberge-Veltheim and Krankenhagen- Möllenbeck in the Wesertal are described and compared considering their depositional and architectural regime. A scenario is developed to explain the genetic sequence of the deposits. The sand-/gravel-body exposed at Krankenhagen-Möllenbeck was deposited first in form of a marginal käme. Subsequently during the Drenthe-stade of the Saale ice age, the sedimentation of the sand- /gravelbody at Hausberge-Veltheim took place under the depositional environment of an end- moraine.

Johann Peter Groetzner im Ruhestand

Biographie und Danksagung an Johann Peter Groetzner

Der Schwermineral-Gehalt von Saale-zeitlichen Moränen- und Schmelzwasser-Ablagerungen des Münsterlandes

This article is a first summary of the heavy-mineral content of moraine and meltwater deposits of the Saalian glaciation in the Münsterland and its northeastern extension (NW Germany). In the beginning the appearance and distribution of both types of sediments are described (E. Speetzen), then the heavy mineral composition of selected outcrops is reported and the results are compared (D. Henningsen). Generally the predominant heavy minerals are garnet, minerals of the epidote group, zircon, and ordinary hornblende. The heavy mineral contents of moraine sediments sometimes are similar to that of meltwater deposits, in other cases they are different. Obviously there exists no relation between the heavy mineral composition and various advances of the Scandinavian ice sheet and their sediments, the content of heavy minerals rather depends on local influences.

Aufbau und Nutzung des Fachinformationssystems Geologie im Niedersächsischen Bodeninformationssystem NIBIS

Digital data from various scientific fields is stored in separate information systems („FIS geology“, „FIS pedology“, etc.) in the Lower Saxony Geo-Information System NIBIS so that it can be processed and interpreted; this is necessary to meet increasing demand for soil-relevant information for decision-making and planning purposes. The necessary work will be considerably accelerated and its quality improved by setting up and actually using such a tool. A detailed account is given of the Lower Saxony Geo-Information System NIBIS, in particular how the data base is set up and how the NIBIS is used in cases where concrete problems occured.

Verteilungsmuster der Mesofauna im hohen Ober-Hauterive Nordwestdeutschlands

The vertical distribution pattem of mesofaunal elements is described from clay-marl bedding rhythms from the Frielingen section (Hannover, NW Germany), which exposes latest Hau- terivian sediments (early Cretaceous). Some mesofaunal groups show a correlation with the pale- dark bedding rhythms. The pale, marly beds are chracterised by bryozoans. In addition remnants of crinoids, echinoids, asteroids, ophiuroids and holothuroids are more common in pale layers than in dark ones. Converseley, the relative abundance of serpulids, fish remains, bivalves and gastropods shows no relationship to the bedding rhythms.

Quantifizierung postholsteinzeitlicher Subrosionen am Salzstock Gorleben durch statistische Auswertung von Bohrergebnissen

The Gorleben salt dome is actually investigated for its suitability as a repository for radioactive waste. It is crossed by a subglacial drainage channel, formed during the Elsterian glaciation (Gorleben channel). Some units of its filling vary strongly in niveau and thickness. Lowest positions and/or largest thickness are found above the salt dome. This is interpreted as a result of subrosion during the Saalean glaciation. The rate can be calculated from niveau differences of sediments formed during the Holsteinian interglacial. However, their position might have been influenced by other factors also (relief of the channel bottom, glacial tectonics, settlement of underlying clay-rich sediments). Their relevance was estimated applying statistical techniques to niveau and thickness data from 79 drillings in the Gorleben channel. Two classes of drillings with features caused by either Saalean subrosion or sedimentary processes during the filling of the Gorleben channel can be distinguished by means of factor and discriminant analysis. This interpretation is supported by the results of classwise correlation and regression analysis. Effects of glacial tectonics on the position of Holsteinian sediments cannot be misunderstood as subrosional. The influence of the settlement of underlying clay sediments can be estimated quantitatively. Saalean subrosion rates calculated from niveau differences of Holsteinian sediments between both classes differ with respect to the method applied: maximum values are 0,83 or 0,96 mm/a, average values are 0,31 or 0,41 mm/a.

Fluviatile und äolische Prozesse im Gebiet der unteren Elbe bei Neuhaus (Niedersachsen) seit dem Weichselspätglazial

The Late Glacial and Holocene landscape development in the vicinity of the River Elbe near Neuhaus, Lower Saxony, was studied during geological mapping of the area. The geological and geobotanical methods used in these investigations were chosen to cope with the difficulties which arise during research on Quaternary flood plains in low country. Paleochannel fill and areas of flood-plain sediments were drilled, the lithology examined, and the sediments dated on the basis of their pollen content. No evidence was found for the existence before the Middle Ages of paleo- channels the size of the present River Elbe. Before the first measures were made to regulate the Elbe River, it was an anastomosing river system with numerous small branches. The lower parts of the flood-plain profiles are predominantly sand and the upper parts silty-clayey loam. With the construction of effective levees over the last several centuries, the flow velocity of the Elbe has increased considerably during high water periods and instead of the deposition of meadow loam, sand was deposited as natural levees. The main belt of sand dunes on the east bank of the Elbe overlies Preboreal to Boreal lake mud and is, therefore, of Holocene age.

Late Devonian (Famennian) jaws: the icriodid multielement apparatus and its function

In this study the conodont multielement apparatus of Late Devonian (Famennian) Icriodus altematus is described which has been reconstructed from clustered group findings and separated elements. This apparatus is markedly different from classical ozarkodinid apparatuses and needs further consideration of its functional morphology. Since bedding plane assemblages of Icriodus altematus are yet unknown, a spatial reconstruction of this apparatus and a feeding mechanism are proposed which are based on the oropharyngal apparatus of recent lampreys. Though the extant representatives of petromyzontoids are not close phylogenetic relatives of extinct conodonts, there exist intriguing analogies concerning the morphology of the tooth types and the presumed spatial distribution within the oral cavity of both taxa.

Entwicklung der Faziesverteilung eines Riffkomplexes im Korallenoolith (Oberjura) des Osterwaldes (Niedersachsen)

The Hainholz quarry in the Osterwald hills of NW-Germany is the most impressive outcrop in the Lower Saxony Basin exposing Late Jurassic (Korallenoolith, Oxfordian) coral buildups. The Korallenoolith deposits in the quarry commence with a oolitic sequence about 20 m thick which is limited by a distinctive hardground at its top. This sequence is overlain by the so called “Obere Korallenbank”-Member about 13 m in thickness which is mainly build up by coral reef complexes. Throughout a lateral extend of about 400 m exposed in the quarry, the Obere Korallenbank Member shows numerous pillar-shaped reefal build ups which are flanked by a reefal debris limestone. The coral fauna of the in situ reefal bioconstructions comprises not less than 37 taxa most of which have been described from the Lower Saxony Basin for the first time. Probably, the pillar-shaped reefs formed a small positive relief of only a few dm against the debris deposits during deposition. The interreef debris limestones in the lower and middle part of the Obere Korallenbank Member show three intercalated biostromal coral layers. In the upper part of the member, the interreef facies is represented by a mikritic peloidal limestone rich in sponge remains and, unusual in such a depositional environment, ammonites (Dichotomo-sphinctes bifurcatoides, D. sp.). Additionaly, at the top of of the peloidal limestone a layer enriched in nerineids and other gastropods limits the reefal constructions of the Obere Korallenbank Member against the overlying “humeralis-Oolith” sequence. On the basis of the facies development of this depositional sequence the reef formation in relation to sealevel changes is discussed.

Paläobiogeographie des Korallenooliths (Mittleres Oxfordium - Unteres Kimmeridgium): Tethyale Faunen- und Florenelement auf höherer Paläobreite

An overview is given here on the palaeobiogeography of the Korallenoolith Formation (middle Oxfordian to early Kimmeridgian) in NW Germany (Lower Saxony Basin). Based on microfacies observations, abundant faunal and floral elements of the tropical tethyan realm are recognized in shallow-marine calcareous sediments of the Korallenoolith Formation. Foraminiferal fauna is both highly diverse and abundant and mostly of mediterranean character. Also, there is a small flora recorded, which includes heavily calcified red algae, aragonitic green algae, and cayeuxiid algae. They display restricted diversity when compared to those of shallow-marine tropical tethyan seas. Chaetetids and diceratids are locally abundant. Lithocodium aggregatum and Bacinella irregularis have been observed in Late Jurassic palaeolatitudes north of the Tethys for the first time. Corals are present in numerous genera and species. Their occurrence is restricted to a few horizons of the Korallenoolith Formation where they build patch reefs, coral biostroms and coral meadows. The overall character of the coral-thrombolite-reefs (florigemma-Bank Member) is very similar to those of the Tethys. The presence of these marine tethyan taxa assigned the position of the Lower Saxony Basin during middle Oxfordian to early Kimmeridgian palaeobiogeographically into the submediterranean province and reflects northward migration of tropical tethyan fauna and flora which reach in the Lower Saxony Basin their northern limit. These biota seem to be biogeo-graphically transitional between communities present in England and the Tethys.