The northern coast of the Ottnangian (middle Burdigalian, early Miocene) Molasse Sea in Germany: sediments, foraminiferal assemblages and biostratigraphy (original) (raw)
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Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 2010
The geology of the lower Miocene Upper Marine Molasse (OMM) of the North Alpine Foreland Basin (Molasse Basin) has been studied intensively. However, one problem that remains concerns the different informal names that have been assigned to the OMM units by local workers. Moreover, there is still no general consensus with regard to the precise lithostratigraphic content of these units. In this study, three outcrops in the Lake Constance area (SW Germany) displaying OMM sediments are investigated with regard to lithofacies, sedimentology and microfossils (benthic foraminiferal assemblages). The Kalkofen Formation is introduced as a formal lithostratigraphic name for the so-called Sandschiefer, which represents a mud-dominated succession of an inner to middle neritic environment. The overlying newly defi ned Baltringen Formation includes the former Bodmansande or Baltringer Schichten, which are sand-dominated deposits indicating a subtidal environment with strong tidal currents. The lower boundary of the Baltringen Fm is marked by a basal erosion surface and a pebbly basal layer (Baltringer Horizont). The Steinhöfe Formation is introduced as a formal lithostratigraphic term for the so-called Deckschichten or Feinsandserie. It overlies the Baltringen Fm and is marked by an unconformity at base. The Steinhöfe Fm comprises fi ner-grained sand/silt alternations indicative of a less high-energetic but still tidally infl uenced marginal marine setting. The abrupt shift between the mud-dominated Kalkofen Fm and sand-dominated Baltringen Fm is a result of the wellknown shallowing-upward event that separates the two classical OMM sedimentation cycles (sensu Lemcke et al. 1953). The unconformity at base of the Steinhöfe Fm adds support to the hypothesis of a third sedimentation cycle. Kurzfassung: Die Geologie der untermiozänen Oberen Meeresmolasse (OMM) im nordalpinen Vorlandbecken (Molassebecken) ist grundsätzlich gut bekannt. Allerdings gibt es für den süddeutschen Anteil des Molassebeckens noch keine lithostratigrafi sche Gliederung der OMM. Stattdessen existieren eine Reihe von informellen Schichtnamen für lokale oder regionale Faziesentwicklungen, deren stratigrafi scher Inhalt nicht immer einheitlich gehandhabt wird. In der hier vorliegenden Arbeit werden drei OMM-Aufschlüsse im Gebiet des Bodensees (SW-Deutschland) hinsichtlich ihrer Lithofazies, Sedimentologie und Mikrofossilien (benthonische Foraminiferen) vorgestellt. Die Kalkofen-Formation wird als lithostratigrafi scher Name für die bisher als Sandschiefer bezeichneten Schichten eingeführt; sie repräsentiert eine überwiegend tonigsiltige Abfolge des inneren bis mittleren Neritikums. Die darüber folgende neu defi nierte Baltringen-Formation umfasst die früher als Bodmansande oder Baltringer Schichten bezeichneten Sedimente; es handelt sich um Sand-dominierte Ablagerungen des subtidalen Bereichs mit starken Gezeitenströmungen. Die Untergrenze der Baltringen-Formation ist durch eine Erosionsdiskordanz und eine basale Gerölllage (Baltringer Horizont) charakterisiert. Für die über der Baltringen-Formation folgenden feinkörnigeren Sedimente, die bisher als Deckschichten oder Feinsandserie bezeichnet wurden, wird der Name Steinhöfe-Formation eingeführt. Die Steinhöfe-Formation zeigt an ihrer Basis ebenfalls eine Diskordanz. Sie besteht überwiegend aus Feinsand/Silt-Wechsellagerungen, die in einem weniger hochenergetischen, aber immer noch Gezeiten-beeinfl ussten Milieu abgelagert wurden. Der sehr deutliche Wechsel zwischen der Ton-Silt-dominierten Kalkofen-Formation und der Sand-dominierten Baltringen-Formation belegt die schon von Lemcke et al. (1953) festgestellte Verfl achung des Beckens, die zur Untergliederung der OMM in zwei Sedimentationszyklen geführt hat. Die Diskordanz an der Basis der Steinhöfe-Formation unterstützt die Annahme eines dritten OMM-Sedimentationszyklus.
Palaeontology, 2004
Six charophyte, 13 mollusc, four ostracod and nine ®sh otolith taxa are taxonomically described, and one fruit, one seed and two foraminiferal taxa are brie¯y noted from the Lower Cyrena Beds and the Lower Coloured Molasse of the Sindelsdorf section near Penzberg (approximately 50 km south of Munich). Our palaeoecological and lithological data from the Lower Cyrena Beds suggest a delta plain with lagoons, estuaries, slowly¯owing rivers, lakes and swamps. Faunal and¯oral elements of the Lower Coloured Molasse indicate lacustrine environments. The gastropod Tympanotonos and the tropical to subtropical ®sh fauna (Eleotridae, Ambassidae and Cyprinodontidae) suggest a warm, at least subtropical climate. Furthermore, Tympanotonos suggests comparisons with Recent molluscan faunas of the mangrove swamps of the West African coast, and thus hints at mangrove vegetation bordering the coasts of the Upper Bavarian Molasse Sea. A biostratigraphical classi®cation for the Oligocene Molasse deposits of the Penzberg Syncline is established for the ®rst time based on otoliths and charophytes. The Lower Cyrena Beds are attributed to the newly de®ned otolith zone OT-O1/2 and probably correspond to the oldest part of the Chara microcera Zone. The lowermost part of the Lower Coloured Molasse can be correlated both with otolith zone OT-O2 and the Chara microcera Zone. The Sindelsdorf section lies within the Rupelian±Chattian transition zone and thus the chronostratigraphic age is approximately 29±28 Ma.
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen, 2009
Evidence for tidal influences in the Upper Marine Molasse (OMM) of the Allgäu area (Southwest German part of the Molasse Basin) is presented. The studied sections in the "Ellhofer Tobel" ravine reveal an approximately 140 m thick succession of marine sediments. Four different facies types are distinguished in this succession: 1) a Glauconitic Sandstone Facies, 2) a Heterolithic Facies, 3) a Cross-Stratified Sandstone Facies and 4) a Conglomeratic Facies. These lithofacies represent different near coastal and shallow marine environments. A tidal influence is indicated by the presence of the Heterolithic Facies which contains associated epsilon cross-stratification and megaripples (or subaquatic dunes). A general current direction from south to north is consistent documented by subaquatic dune foresets and the orientation of ripple foresets. If the coastal environment near the southern coast of the Molasse Sea had a rather simple tidal current regime this dominant northerly current direction could be interpreted as ebb currents.
Fossil Record
Albian to Turonian carbonate deposits at three different locations of the Lower Saxony Cretaceous and thereby of the European mid-Cretaceous epeiric shelf sea were investigated for their fossil agglutinated foraminiferal fauna. In this study, 71 samples from two quarries and three drill cores were treated with formic acid, which enabled the study of agglutinated foraminiferal assemblages even in highly lithified limestones. In total, 114 species were determined and classified as belonging to nine morphogroups. In general, four agglutinated foraminiferal assemblages are distinguished: (1) an uppermost Albian-lowermost Cenomanian assemblage from the Wunstorf drill cores, with the dominant taxa Bathysiphon spp., Nothia spp., Psammosphaera fusca, Reophax subfusiformis, Bulbobaculites problematicus, Tritaxia tricarinata, Flourensina intermedia, Vialovella frankei, Arenobulimina truncata, and Voloshinoides advenus; (2) a Cenomanian assemblage from the Baddeckenstedt quarry and Wunstorf drill cores, with Ammolagena clavata, Tritaxia tricarinata, Vialovella frankei, Arenobulimina truncata, and Voloshinoides advenus; (3) an assemblage related to the Cenomanian-Turonian Boundary Event in Wunstorf and Söhlde dominated by Bulbobaculites problematicus; and (4) a Turonian assemblage in the Wunstorf and Söhlde sections with high numbers of Ammolagena contorta, Repmanina charoides, Bulbobaculites problematicus, Gerochammina stanislawi, and Spiroplectammina navarroana. The latest Albian-earliest Cenomanian assemblage consists of tubular, globular, and elongate foraminiferal mor-phogroups which are typical for the low-to mid-latitude slope biofacies. All other assemblages are composed of elongate foraminiferal morphogroups with additionally globular forms in the proximal settings of Baddeckenstedt and Söhlde or flattened planispiral and streptospiral forms in more distal settings of Wunstorf. For these assemblages, a new agglutinated foraminiferal biofacies named "mid-latitude shelf biofacies" is proposed herein. Changes in the relative abundance of different morphogroups can often be referred to single features of depositional sequences. Furthermore, classical macro-bioevents, which are often depositional-related, of the Lower Saxony Cretaceous seem to have a micro-bioevent or acme equivalent of the agglutinated foraminiferal fauna.
Late Albian benthic foraminiferal biofacies and paleogeography of Northeast Germany
Neues Jahrbuch Fur …, 1999
Well preserved upper Albian to lower Cenomanian benthic foraminiferal assemblages from 153 samples of five cored wells in eastern Germany contain 119 species. Multivariate statistics (cluster analysis and principal components analysis) allow to discriminate four distinct biofacies: "Textularia-biofacies", "Laevidentalina-biofacies", "Glomospira-biofacies" and "Saccammina-biofacies". The paleogeographic distribution of these four biofacies reflects the change from highly terrigenous influenced environments in the south to more open marine conditions towards the north. A trend is observed from higher terrigenous flux and resulting substrate disturbance in the early late Albian towards open pelagic conditions with increased primary productivity in the latest Albian and early Cenomanian. This trend is reflecting transgressive cycles, which are superimposed by Milankovitch-frequency fluctuations in benthic diversity and biofacies. This temporal and spatial distribution of the benthic foraminiferal biofacies was probably controlled by fluctuating primary productivity and changes in terrigenous flux.
Austrian Journal of Earth Sciences
Abstract The northern Tethyan margin is a key region for determining environmental changes associated with the collision of continental and oceanic tectonic plates and Alpine orogeny. Herein we investigated Middle to Late Eocene neritic to bathyal sediments depo- sited during an interval of unstable climatic conditions. In order to quantify paleoenvironmental changes, we developed a detailed age model based on biozonations of planktic foraminifera, calcareous nannoplankton, and larger benthic foraminifera. The section at Adelholzen covers the almost complete Lutetian Stage (calcareous nannoplankton zones NP15a-16, planktic foraminifera zones E8-11, shallow benthic (foraminifera) zones SBZ13-15) and large parts of the Priabonian Stage (NP18-20, E14/15), while the inter- mediate Bartonian Stage (NP17) is completely missing. Foraminiferal, calcareous nannoplankton, and macrofossil assemblages were analyzed for changes in paleo-water depth, mixing and stratification, paleo-primary produ...
Newsletters on Stratigraphy
For Oligocene and Miocene sediments of the Central Paratethys realm, regional chronostratigraphic stages have been defined on the basis of characteristic faunal assemblages, often containing abundant endemic elements. Although considerable progress has been made in correlating Paratethyan stages with the Global Time Scale (GTS), the task remains incomplete, especially for the Early Miocene period. The present study focuses on Lower Miocene deposits of the Central Paratethys in southeastern Germany, i. e. the Upper Marine Molasse (OMM) and Upper Brackish Molasse (OBM) of the North Alpine Foreland Basin (NAFB, Molasse Basin). The sediments concerned are assigned to the regional Ottnangian stage of the Central Paratethys, which corresponds to the middle Burdigalian in the GTS. We present a formal lithostratigraphic definition of the Untersimbach and Neuhofen Formations (both OMM), combined with litho-, bio-and magnetostratigraphic investigations, which together provide an improved chronology for the middle Burdigalian interval in the NAFB. The base of the Ottnangian stage is shown to correlate with polarity chron C5En, and we consider an absolute age of around 18.2 Ma to be most plausible. As the OMM in the southeast German part of the NAFB represents a single transgressive-regressive sequence, our new data suggest that the Ottnangian transgression began during chron C5En (~18.2 Ma), whereas the onset of the regressive phase lies within chron C5Dr.2r (~18 Ma). The uppermost marine deposits (top OMM/"Glaukonitsande & Blättermergel") and the lowermost brackish sediments (OBM/Oncophora Formation) are correlated with polarity chron C5Dn (~17.4 Ma). Moreover, our results clearly demonstrate that the lower Oncophora Formation (normal polarity) is not time-equivalent to the OBM/Kirchberg Formation in the southwest German sector of the NAFB (largely reverse polarity) as has hitherto been assumed. The lower Oncophora Formation is most probably contemporaneous with the lowermost OBM sediments (Grimmelfingen Formation) in the southwest German Molasse Basin.
Palaeontologia Electronica, 2023
The Early Miocene Upper Marine Molasse (OMM) in southwestern Germany contains a diverse fossil ecosystem in which elasmobranch teeth are especially abundant. However, the scarcity of outcrops and sometimes poor preservation of fossils resulted in scant recent literature about the OMM. Here, we focus on the elasmobranch fauna to determine the trophic relationships within the OMM, using fossil teeth as proxies for diet and trophic levels based on functional morphology and an actualistic species-or genus-level approach. Herein we present a fresh and comprehensive palaeoecological reconstruction of the OMM ecosystem in Baden-Württemberg. All five outcrop areas available for the present analysis (Baltringen, Meßkirch-Rengetsweiler, Meßkirch-Walbertsweiler, Ulm-Ermingen, and Ursendorf) exhibit a similar faunal composition, with the apex predator being Otodus (Megaselachus) sp. Among the other elasmobranchs, there are mostly piscivorous and malacophagous species; taxa that feed on a variety of other invertebrates or amniotes (including marine mammals) are also present. The OMM sediments deposited in shallow-water settings, but there are fossils of more oceanic species that might, at times, have approached the shore. With a soft bottom, partly covered by sea grass, the OMM environment would have been like the present-day warm-waters settings of the Mediterranean.