Dirk Munsterman

Sodium polytungstate, a new non-toxic alternative to bromoform in heavy liquid separation

Abstract Bromoform, one of the most commonly used heavy liquids in palynological preparation, is highly toxic. The alternatives currently in use all have drawbacks. In this study a new non-toxic alternative, sodium polytungstate, has been compared to bromoform. 36 core samples of sandy clay or clayey sand were analysed from boreholes in the eastern Netherlands. Both marine and terrestrial settings are represented. The results show similar sporomorph recovery using both heavy liquids provided that specific gravity 2.1 is used, while surprisingly, dinocyst recovery shows a marked improvement with sodium polytungstate. In particular the variation in dinocysts present in low frequencies increases. When both liquids were tested at a specific gravity of 2.4, the number of sporomorphs decreased while the concentration of other organic matter increased.

Integrated chronostratigraphy of the Pliocene-Pleistocene interval and its relation to the regional stratigraphical stages in the southern North Sea region

Time-stratigraphic interpretations of Late Pliocene to Early Pleistocene sediments from onshore locations and from marginal marine settings of the North Sea Basin often refer to the subdivision of the Dutch and British ‘Quaternary’ regional stratigraphic stages. Since age control for these stages and their stage boundaries are based on relative dating methods, in this study pollen, dinoflagellate cysts and foraminiferal assemblages were investigated to correlate the regional stratigraphic stages independently to the global chronostratigraphy and the paleomagnetic timescale. The data were obtained from eight boreholes located in the depocentre setting of the Late Pliocene North Sea Basin comprising a 1000 m thick sedimentary succession. The British Gedgravian and Waltonian stages, the Dutch Reuverian to Brunssumian as well as published foraminiferal zones (NSB 14, FB and the lower part of the FA2 zone) fall within the Zanclean and Piacenzian. The lower boundaries of the Pre-Ludhamian and Pretiglian stages and of the NSB 14 to 15 zones are close to the paleomagnetic Gauss-Matuyama boundary. The Pre-Ludhamian, Ludhamian, Thurnian and the Pretiglian, Tiglian A and Tiglian B stages presumably cover the marine isotope stages 103 to 95. It is proposed that the Ludhamian, Thurnian and the Tiglian A were short lasting, warm, periods during which sea level highstand facilitated sedimentary deposition at the marginal areas of the North Sea Basin. The lower boundary of the paleomagnetic Olduvai subchron is situated in the Tiglian C1-4b stage while the TC4c stage is found within the Olduvai subchron. Foraminiferal NSB 15 and NSB 16 zone as well as the upper part of the FA2 and FA1 zone fall within the Gelasian and cover the Matuyama chron as well as the lower part of the Olduvai subchron. Comparison with formerly dated North Sea sediments shows a good agreement between foraminiferal zonations on a broader scale but significant differences in absolute ages occur. Strontium isotope values indicate approximately 1 Ma younger ages as expected from our chronostratigraphic model. This discrepancy is explained by the dominance of freshwater from river discharge contributing high amounts of eroded material to the basin, leading to an increase of the 87 Sr/ 86 Sr ratio in the shelf-sea water.

Revision and update of the Callovian-Ryazanian Stratigraphic Nomenclature in the northern Dutch offshore, i.e. Central Graben Subgroup and Scruff Group

Exploration in a mature basin requires a detailed classification and standardisation of rock stratigraphy to adequately comprehend the depositional history and prospect architecture. The pre-Quaternary Stratigraphic Nomenclature of the Netherlands compiled by Van Adrichem Boogaert &Kouwe in 1993 provided a consistent framework for use by the Dutch geological community. Over the past twenty years, new biostratigraphic techniques and continued exploration in the Netherlands have provided additional stratigraphic information. Based on this information the Late Jurassic lithostratigraphy in particular, shows significant inaccuracies. The Callovian-Ryazanian strata from the northern offshore of the Netherlands’ territorial waters, termed the Central Graben Subgroup and Scruff Group, reveal a complex sedimentary history. The combination of non-marine to shallow marine lateral facies changes, repetitive log and facies characteristics in time, sea-level and climate change, salt tectonics and structural compartmentalisation hamper straightforward seismic interpretation and log correlation. Recognition of three genetic sequences by Abbink et al. in 2006 enabled an improved reconstruction of the geological history. Further improvements in refinement and reliability of the stratigraphy together with new information on the facies and ages of the successions and about the subsequent tectonostratigraphic development of the northern Dutch offshore area form the basis of the present revision. As a result, earlier lithostratigraphic models have been changed and new lithostratigraphic relationships and names are introduced in this paper.

Late Cenozoic shelf delta development and Mass Transport Deposits in the Dutch offshore area - results of 3D seismic interpretation

In this study, seismic stratigraphic criteria have been used to characterise the evolution of the Southern North Sea (SNS) shelf-delta system that progressively filled the Southern North Sea basin during Plio-Pleistocene times. Based on the prograding and down-stepping architecture of the shelf-delta sequence it is inferred that deposition occurred during a time of high sediment supply and overall sea-level lowering. During this time the delta slopes failed several times, creating at least 30 internally coherent Mass Transport Deposits (MTDs) mainly grouped in common areas, affecting the same clinoform set and partially sharing the basal shear surface (groups of MTDs). The most important features of the studied MTDs are 1) the dominance of brittle deformation; 2) the small amount of material removal from the headwall domain (lack of completely depleted areas above the basal shear surface); and 3) the lack of an emergent toe domain above the un-failed sediment located basinward, although proper confining geometries for the MTD are not detected. Therefore, the studied MTDs can neither be classified as frontally confined nor as frontally emergent but they are a new intermediate type of submarine landslides which has not been described before. These characteristics suggest that the mass movement ceased relatively soon after initiation of failure. Incisions on top of the MTDs suggest the presence of erosive flows. These flows were probably generated due to a concentration of the drainage in the negative morphology the failure event left behind in the upper sector of the slope. The stronger progradational character of the reflections on top of MTDs confirms a concentration of drainage after the erosional phase too. The interplay between high sediment supply and constant or even decreasing accommodation space (caused by constant or decreasing sealevel) is supposed to be the main precondition for slope instability for most of the MTDs in this study area. Slope failures themselves can also be considered a preconditioning factor by the creation of local very high sedimentation rates (see groups of MTDs). Salt-induced seismicity and storm waves’ effect superimposed on high frequency sea level fall are considered the most important triggering factors.

Dinoflagellate cyst biostratigraphy of Miocene strata in the Adana Basin, Eastern Mediterreanean, Turkey

abstract The Adana Basin is one of the major Neogene basins situated in SW Turkey with sedimentary successions providing good records of the paleoenvironmental changes that affected the Mediterranean area. Since a detailed biochronostratigraphic framework has not been properly established in the Adana Basin yet, this study will be the first multidisciplinary approach carried out in this region. In addition, a detailed biozonation based on marine palynomorphs was the first ever documented from the Köpekli Formation deposited during the Miocene (from late Burdigalian to Langhian) and the established biozones were correlated with those of planktonic foraminifera and calcareous nannofossils. According to the first occurrences (FOs) and the last occurrences (LOs) of selected taxa, five biozones (P-1, P-2, P-3, P-4 and P-5) based on dinoflagellate cysts; five biozones (M4a, M4b, M5a, M5b and M6) based on planktonic foraminifera; and two biozones (NN4 and NN5) based on calcareous nannofossils were established in the Miocene Köpekli Formation. In order to achieve a worldwide biostratigraphic perspective based on dinoflagellate cysts, the present biozones were compared with those described from NW Europe (Denmark, Germany, the Netherlands), the East Coast of the US and Egypt. After calibration to the established Turkish foraminifera and nannofossils standard, the palynological analysis shows that the recorded dinoflagellate cysts events (e.g. FO of Labyrinthodinium truncatum, Cerebrocysta poulsenii and Unipontidinium aquaeductus and LO of Palaeocystodinium ventricosum) occurred chronostratigraphically earlier in SE Turkey than in NW Europe and on the East Coast of the US.

Late Jurassic Rifting in the Southern Central Graben - A Complex Story Simplified

In order to be able to predict the distribution of reservoir sands and of grainsize and porosity trends in a hydrocarbon province, it is essential to understand the basin evolution in detail. In this study, an attempt is made to reconstruct the complex basin evolution of the southern Central Graben area by careful correlation of sedimentary successions from the different structural elements. The Late Jurassic rift phase is complex: a change in tectonic regime occurs, subsidence varies dramatically through time and space and former depocenters may become sources for erosion. In this paper a break down is proposed for the basin evolution in three discrete steps, each of which is closely related to changes in the tectonic regime. The basin fill of the southern Central Graben area is displayed in Wheeler type of diagrams, showing the facies relationships between the various parts of the basin.