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.

Gewebeansatz-Strukturen auf pyritisierten Steinkernen von Ammonoideen

3400 pyritized internal moulds of Upper Devonian, Triassic, Jurassic and Lower Cretaceous ammonoids show various soft tissue attachment structures. They are preserved as regularly distributed black patterns on the moulds. All structures can be interpreted as attachment areas of muscles, ligaments and intracameral membranes. Paired structures are developed along the umbilicus and on the flanks of the moulds, unpaired ones appear on the middle of their dorsal and ventral sides. Strong lateral muscles cause paired twin lines on the flanks of the phragmocone and of the body chamber. A ventral muscle is deduced from small rounded or crescent shaped spots in front of each septum on the ventral side. These spots are often connected, forming a band-like structure. Broad dark external bands on the ventral side of the phragmocone, ventral preseptal areas in the posterior part of the living chamber, small twin lines or oval shaped areas on the ventral side of the living chamber represent paired or unpaired attachment areas of the hyponome muscle. A middorsal muscle is documented by small roughened areas in front of each dorsal lobe. Dark spots along the umbilicus, often connected and thus forming a band-like structure (tracking band), are remains of a pair of small dorsolateral muscles at the posterior end of the soft body. Dark bands, lines and rows of small crescent shaped structures behind the tips of sutural lobes are due to spotlike fixation places of the posterior part of the mantle and their translocation before subsequent septal secretion. Devonian goniatites had a paired system of lateral and ventrolateral muscles preserved on the moulds as black or incised lines on the flanks of the living chamber and as dark preseptal areas, ventrally indented. These structures represent the attachment areas of paired lateral cephalic and paired ventral hyponome retractors. Fine black lines on the phragmocone situated parallel to the sutures (pseudosutures) represent a rhythmical secretion of camera! membranes during softbody translocation. Goniatites had a paired system of lateral and ventrolateral muscles, whilst Neoammonoids have a paired lateral and dorsolateral system, and, additionally, an unpaired system on the ventral and on the dorsal side. Mesoammonoids show only a paired lateral and an unpaired dorsal one. Fine black lines situated parallel to the saddles and behind the lobes of the suture line can be interpreted as structures left during softbody translocation and a temporary attachment of rhythmical secreted cameral membranes. Cameral membranes had supported the efficiency of the phragmocone. Only some of the observed structures are also present in recent Nautilus. Differences in the form and position of attachment sites between ammonoids and recent Nautilus indicate different soft body organizations between ammonoids and nautiloids. The attachment structures of goniatites especially of tornoceratids can be compared with those of Nautilus which indicates Richter - Gewebeansatz-Strukturen bei Ammonoideen 3 a comparable mode of life. Differences in the form and position of attachment structures between goniatites and ammonites may indicate an increasing differentiation of the muscular system in the phylogeny of this group. Different soft body organization may depend on shell morphology and on a different mode of life. On the modification or reduction of distinct muscle systems ammonoids can be assigned to different ecotypes. Based on shell morphology and the attachment areas of cephalic and hyponome retractor muscles two groups can be subdivided: - Depressed, evolute morphotypes with longidome body-chambers show only small ventral hyponome retractor muscles. Lateral cephalic retractors are not developed. These morphotypes are adapted to a demersal mode of life. Without strong cephalic retractor muscles no efficient jet propulsion can be produced. These groups represent vertical migrants with efficient phragmocone properties (multilobate sutures, cameral membranes, narrow septal spacing). - Compressed, involute moiphotypes with brevidome body-chambers show strong cephalic and hyponome retractor muscles and represent a group of active swimmers. These morphotypes were able to live at different depths, in the free water column or/and near the seafloor. They are not confined only to one habitat. Most of the examined genera and species belong to this group. Changes of the attachment structures in the course of ontogeny confirm that juveniles of Amaltheus and Quenstedtoceras lived as passive planche drifters in upper and intermediate parts of the free water column after hatching. At the end of the juvenile stage with a shell diameter of 0,3 - 0,5 cm cephalic retractor muscles developed. With the beginning of an active swimming mode of life (neanic stage) the subadult animals left the free water column and moved into shallow water habitats. Fuciniceras showed no marked changes in the attachment structures during ontogeny. This indicates that there occur no differences in the mode of life between juvenile and adult growth stages. Based on attachment structures and shell morphology of Devonian goniatites their relation to the systematic position permits statements about probable phylogenetic relationships between the Cheiloceratidae and Tornoceratidae. In some cases attachment structures of ammonites permit statements about phylogenetic relationships on family and genus level.

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.

Bryozoan borings in shells of Costa Rican miocene oysters

Borings of bryozoan colonies are rare fossils and hitherto unknown from Central America. Four different types of zoaria, belonging to Spathipora sp., Terebripora sp. A, Terebripora cf. falunica and Iramena sp., were recognized. They are developed on shells of Miocene oysters (Saccostrea sp. and Ostrea sp.) from shell - beds of the Venado-Formation (Northern Limon - San Carlos Basin, Costa Rica). The period of colonization and growth by bryozoans and/or a few other benthic invertebrates was probably a short - term event, followed by suffocation from accumlating sediment.

Age an origin of the "Mexican Onyx" at San Antonio Texcala (Puebla, Mexico)

A great variety of color banded CaC03 is known as „Mexican Onyx“, and is extensively used for ornamental purposes. Within the San Antonio Texcala mining district an area of about 24.000 m2 is covered by a thick travertine crust with a calculated volume of at least 2,8 x 1061. It originates from warm waters that emerge on young fissures and faults. It seems to be likely that the travertine formation is related to the hydrothermal activity of the Transmexican Volcanic Belt and to the seismicity of this zone. The deposit is built up by different travertine varieties. The main lithotypes are: (1) dense crystalline laminated travertine; (2) ray crystal travertine; (3) shrub layer travertine; (4) irregular porous travertine; (5) travertine breccia. Textural variation seems to be related to water temperature/distance from the emergence point, rapid or slow degassing of CO, and bacterial influence. At the moment, a light green banded variety (native sulfur impurities) is mined. It is the facture fill of a morphological prominent fissure-ridge travertine. U/Th data indicate, that the travertine has been deposited since at least 52 + 5 ka.

Teeth of a small durophagous crocodile from the Late Jurassic (Kimmeridgian) of North Germany

An outcrop of Late Jurassic (Kimmeridgian) age in Lower Saxony (NW Germany) has yielded small teeth probably of crocodilian origin. The dental morphology is still unknown among crocodiles and indicates a durophagous habit. The teeth are provisionally referred to as Metasuchia fam., gen. et sp. indet.

Hydrothermale Dolomitisierung im Kauffunger Kalkstein (Paläozoikum - W-Sudeten, Polen

Within the Kauffung Limestone dolomite bodies related to volcanic contacts occure and are interpreted as a post-Variscan, hydrothermal volcanogenic formation. Two genetic dolomite types are discernible: a pervasive replacement saddle dolomite and a cavity filling saddle dolomite cement. Micro texture and oxygen isotopy of both dolomite types refer to heightened temperatures of formation. The ocurrence of the dolomite in contact to cross-cutting rhyolithic dikes points to a close petrogenetic relation. Dolomite bodies and rhyolithic injections in contrast to the rock wall are characterized by a distinctive cavernous texture, so that a prekinematic genesis is excluded. The formation of replacement saddle dolomite and saddle dolomite cement altogether are considered as a concomitant phenomenon of the Permo-Carboniferous volcanism widespread in the Bober-Katzbach Mountains.

Der Kauffunger Kalkstein (Bober-Katzbach Gebirge, Polen): Petrographie, Fossilinventar, Stratigraphie

In the Western Sudetes (Mts.) in SW Poland carbonate rocks occur which are well known in the older German literature as ’’Kauffung Limestone” or ’’Wojcieszow Limestone” in recent publications, respectively. They are intercalated in sedimentary (shales) and volcanic (greenstone) successions and are, presumed - due to the lack of index fossils - to be Cambrian in age. These deposits occur in a variety of isolated massifs in the Bober-Katzbach Mts. where they have been mined in many quarries in the past. In a single location (Polom quarry near Wojcieszow) they are exploited up until today. The predominantly calcitic rocks display a wide variety of different lithologies and are, consequently, subdivided into the following lithological units which differ in textural characteristics, mineral constituents, and different grades of diagenetic and metamorphic alteration: 1. Calcite Marble: massive, calcitic, chiefly metamorphic recrystallized. 2. Zebra Limestone: dolomitic-calcitic, certain content of metasomatic silica, fine bedding as a result of microbial calcite precipitation or of diagenetic to metamorphic separation of carbonate and silica constituents. 3. Massive matrix Dolomite: compact, of diagenetic to metamorphic origin. 4. Dolomite Marble: metamorphic. 5. Hydrothermal Dolomite: hydrothermal alteration of limestone, postdating the tectonic deformation. The recent appearance of ’’Kauffung Limestone” is mainly a result of regional metamorphosis at low temperature up to about 300°C and locally high pressure. The typical textural features are stress induced, mostly protomylonitic calcite recrystallisation and generally slowly or not infected dolomite crystals. The different reactions of the two carbonate phases are attributed to their mineral properties. Rhyolitic and dacitic dykes penetrating the carbonate rocks are interpreted as a result of post- orogenic, probably Carboniferous or Permian volcanism. Microprobe investigation on the carbonates revealed a stochiometric composition of dolomite and calcite. The stable isotope content (8 c 0,8* ^C) reflects increased crystallisation temperature of the carbonate minerals (8 O von -7,75 bis -15,78). A variety of fossil remains have been extracted from bulk samples, consisting of sponge needles, floral components, foramini- fera, and vertebrate remains the latter two of which indicate a depositional age younger than Ordovician. Due to the stratigraphic re-attribution of the Kauffung Limestone, the hypothesis of a Cambrian/Ordovician rifting in the Western Sudetes should be abandoned.

Beurteilung der geomechanischen Stabilität und Integrität von Endlagerbergwerken im Salzgebirge auf der Grundlage geologischer und ingenieurgeologischer Untersuchungen

Any safety assessment of a permanent repository for radioactive waste has to include an analysis of the geomechanical stability of the repository and integrity of the geological barrier. Such an analysis is based on geological and engineering geological studies of the site, on laboratory and in-situ experiments, and on numerical calculations. Central part of the safety analysis is the geomechanical modelling of the host rock. The model should simulate as closely as possible the conditions at the site and the behaviour of the rock (e.g., geology, repository geometry, initial rock stress, and constitutive models). On the basis of the geomechanical model numerical calculations are carried out using the finite-element method and an appropriate discretization of the repository and the host rock. The assessment of the repository stability and the barrier integrity is based on calculated stress and deformation and on the behaviour of the host rock measured and observed in situ. An example of the geomechanical analysis of the stability and integrity of the Bartensieben mine, a former salt mine, is presented. This mine is actually used as a repository for low level radioactive waste. The example includes all necessary steps of geological, engineering geological, and geotechnical investigations.

Zur Biostratigraphie und Fazies der Unterkreide-Serien (Hauterivium - Aptium) im Eisenerz-Tagebau "Morgenstern" N-Goslar (SE-Niedersachsen)

Im aufgelassenen Eisenerz-Tagebau "Morgenstern" wurde zwischen liegendem Erz und hangendem "Gaultkonglomerat" ein ca. 58 m mächtiger Schichtkomplex lithologisch und biostratigraphisch bearbeitet. Die Schichtglieder konnten anhand der begleitenden Megafauna (Belemniten, Ammoniten) und in Verbindung mit der Mikrofauna (Foraminiferen) stratigraphisch eingestuft werden. Die Foraminiferenfauna aus 93 Mikroproben wurde bearbeitet und im Sinne von MICHAEL (1974) palökologisch analysiert. Die aufgeschlossenen Schichtglieder gehören dem höchsten Mittel- Barremium (Zone des "Crioceras" sparsicosta), dem Ober-Barre- mium sowie dem Aptium an. Das Ober-Barremium konnte in die Zone des Simancyloceras stolleyi und die Zone des Parancyloceras bidentatum & P. scalare gegliedert werden. Innerhalb des Aptium konnten die beiden Unterstufen gegeneinander abgegrenzt werden; eine Ausgliederung der Zonen war hier jedoch nur teilweise und unter Vorbehalt möglich. Der aufgeschlossene Teil der Erzfazies bleibt auf das oberste Mittel-Barremium (Dachbereich des "Hauptlagers") und die stolleyi- Zone des Ober-Barremium ("Hangendes Lager" und "Zwischenlager") beschränkt; die Lager sind somit jünger als bisher von älteren Autoren (z.B. KOLBE 1962, 1970; NEUMANN 1964) angenommen wurde.

Die Feldspatgehalte quartärzeitlicher Sande Niedersachsens

The feldspar contents of 373 samples from quaternary sands of Lower Saxony (West Germany) were determined. The samples were taken in all parts of Lower Saxony and represent a selec- tion of quaternary Sediments of different age and genetic origin. 7 different methods of investigation were tested to determine the content of feldspar both qualitative and quantitative. Polarizing mioroscopy, x-ray diffractometry, Chemical analysis and staining fit these aims best. The most important results of these investigations are: - The quarternary Lower Saxonian sands have an average content of 4.4 weight-% potassium feldspars and 0.8 weight-% plagio- clase. - All tested samples have a similar qualitative feldspar compo- sition. There are monocline, tricline and - more rare - per- thitic potassium feldspars with a rather high (greater 80 %) KAlSi3O8 content. From the plagioclase feldspars only albite, oligoclase and little andesine were indicated. - The potassium feldspar content is higher in each sample than the plagioclase content. - The feldspar content depends on age and genetic origin of each sand. Generally spoken the feldspar content lessens with increasing age. Glaciofluviatile and basin sands usually have a higher feldspar content than fluvial or aeolian sands of the same age. - The feldspar content is highly influenced by grain size com- position. A minimum of feldspar content lies between 0.4 and 1 .0 mm grain size. Fine sands usually have a higher feldspar content than coarse sands. The reason for this phenomenon is weathering. - There are no regional differences in the amount of feldspar content. - The feldspar content is not high enough for commercial mining.