Abstract The Paleocene Siri Canyon extends for more than 120 km from the Stavanger Platform to the Tail End Graben along the Danish-Norwegian North Sea boundary. Initial formation of the canyon system took place in the Early Paleocene (Danian) and was related to major, submarine sliding in the uppermost chalk section caused by uplift of the Scandinavian hinterlands. The trend of the canyon partly follows salt structures along the southern edge of the Norwegian-Danish Basin (part of the Northern Zechstein Basin). The canyon fill consists of deep-marine, highly glauconitic sandstones interbedded with hemipelagic and turbidite marls and mudstones. As for many Paleocene deep-marine sandstones in the North Sea, the sandstones of the Siri Canyon are massive and blocky. Frequent occurrence of injected sandstone sills/dykes, injection breccias, as well as erosion and associated rip-down clasts along the upper boundaries of in situ sandstones, indicate thorough, post-depositional modification. Fluidization is, thus, likely to be the main reason for the general scarcity of primary sedimentary structures and massive appearance of the sandstones. All sandstones are basically free of detrital clays and most likely formed from non-cohesive, concentrated density flows probably developed as turbidity currents. The sand flows were confined by the canyon and the depositional pattern indicates a complex interaction of turbidity currents, salt-induced seafloor topography and differential compaction. Release of sandy flows was probably caused by seismic shocks resulting in a collapse of unstable shelf sands concentrated on the Stavanger Platform. Transport distances of the sands were up to 120 km and thereby contrast with many Paleocene submarine sandstones in the North Sea. The deep-marine play in the Siri Canyon relies on long distance migration of hydrocarbons, up to 75 km from mature Jurassic source rocks in the Central Graben. This was facilitated by the elongate and confined geometry of the sandstones forming a well-connected system for updip migration.

Abstract Seismic reflection data from the Danish North Sea are interpreted to map the structure of the Palaeozoic basement in the area of the MONA LISA deep seismic lines. Based on a characteristic near-basement reflection, the upper crystalline crust of Baltica of offshore Denmark is traced to the south into the southern Horn-Graben, and to the west to the eastern shoulder of the Central Graben. A two-way-traveltime map of the near-basement horizon and several interpreted seismic sections reveal that three main tectonic events influenced the topography of the basement: (1) a compressional event which could be Caledonian in age; (2) a Palaeozoic extensional event postdating the compressional deformation and expressed in a system of WSW-ESE to W-E striking Palaeozoic half-grabens; and (3) the Permo-Triassic rifting that led to the formation of NNW-SSE to NNE-SSW trending Mesozoic faults of the Horn Graben and the Central Graben which are oriented sub-perpendicular to the Palaeozoic system. Compressive deformation is localized in a narrow zone around and south of the hitherto interpreted Caledonian Deformation Front and foreland deformation on Baltica is suggested as its origin. The seismic image of the Palaeozoic halfgrabens indicates that the East North Sea High is an inverted Palaeozoic rift which subsequently was cut by younger Late Palaeozoic to Mesozoic rifts of the Horn and Central Grabens. The timing of the first extensional phase remains speculative, but it predates the Rotliegend unconformity. Some of the older Palaeozoic normal faults may have been reactivated as transfer zones between the different graben segments during the Permo-Mesozoic extension.

Abstract Since the original MacLeod and Keller (1991a, b) graphic correlation study of Cretaceous/Tertiary (K/T) boundary sections and cores, new biostratigraphic data have become available for lowermost Danian successions in high latitudes (Nye Kj0v, ODP sites 690 and 738) and from sequences proximal to the proposed Chicxulub impact structure (Millers Ferry, Mimbral). Graphic analysis of these data provides an opportunity lo test the prediction that rising eustatic sea level during the tians-K/T interval played a major role in Controlling pattems of sediment accumulation in neritic and bathyal settings. In addition, restricling the empirical basis for development of a lowermost Danian Composite Standard (LD-CS) from all available biostratigraphic data (used in the previous study) to only datums from widely-accepled Danian and K/T survivor laxa enables determination of the extent to which previous results were biased by inclusion of data from controversial “Cretaceous” survivor taxa. Results indicate that sequences from neritic and upper bathyal settings (Nye Kİ0V, Mimbral) are temporally complete within their lowermost Danian intervals while sections/cores from very shallow inner neritic settings (Millers Ferry) and the deep sea (ODP Site 690, ODP Site 738) contain incomplete lower Danian stratigraphic records. These findings are consistent wilh results of traditional zone-based biostratigraphic analyses and with predictions of the sequence stratigraphic model. Moreover, this revised LD-CS is essentially identical to the previous K/T-CS (MacLeod and Keller, 1991b) based on total biotic data. Data from a large number of organismal groups now confirm that biotic, sedimentologic, and geochemical studies based solely on deep-sea and very shallow neritic successions are biased toward catastrophic paneras of change as a result of missing section (= time). Biotic patterns from inner neritic through upper bathyal settings have the best chance of preserving temporally complete sequences of lower Danian events. The faunal record from these sequences reveals the lower Danian succession to be characterized by progressive rather than instantaneous turnover in biotic, sedimentologic, and geochemical variables occurring over at least 500,000 years.

Abstract A review is given of recently published and new data on Avalonia east of the Midlands Microcraton. The three megasequences from Cambrian to mid Devonian described in Wales and Welsh Borderland are also present east of the Midlands Microcraton (Brabant Massif, Condroz, Ardennes, Remscheid and Ebbe inliers, Krefeld high). The three megasequences are caused by a tectonic driving mechanism and are explained by three different geodynamic contexts: an earlier phase with extensional basins or rifting and rather thick sequences, when Avalonia was still attached to Gondwana; a second phase with a shelf basin with moderately thin sequences when Avalonia was a separate continent and a later phase with a shelf or foreland basin development and thick sequences. Deformation of the megasequences 1 and 2 or 1 to 3 varies between areas. In Wales and the Lake District the Acadian phase is long-lived and active from early to mid Devonian. In the Ardennes inliers a deformation is active between the late Ordovician and the Silurian (Ardennian Phase), with a similar intensity as the core of the Brabant Massif, when present erosion levels are compared. The Brabant Massif is partly deformed by the long-lived Brabantian Phase from late Silurian till early mid Devonian. Both the Ardennes inliers and the Brabant Massif are not classic orogenic belts, only slate belts where no more than the epizone is reached at present erosion levels. Areas supposedly close to the microcraton or basement are nearly undeformed (SW Brabant Massif and central Condroz). A model of anticlockwise rotation of Avalonia of about 55° from Caradoc to Emsian is proposed to explain the deposition setting of megasequence 3 and the subsequent Acadian and Brabantian deformation. Immediately after the Avalonian microcontinent touched Baltica in Caradoc times it created a short-lived subduction magmatic event from The Wash to the Brabant Massif and soon after the magmatism ended a foreland basin developed. Possibly during and after that development a long-lived and slow compressional event occurred, leading to the deformation of the Anglo-Brabant Deformation Belt. In the early Devonian, contemporaneous with the shortening of the Anglo-Brabant Deformation Belt, extension occurred in the Rheno-Hercynian Zone, possibly caused by the same slow rotation of Avalonia. More evidence emerges that Avalonia east of the Midlands Microcraton comprises not one but probably two terranes: the remnant of the palaeocontinent Avalonia, and what is called the palaeocontinent Far Eastern Avalonia; the latter is only occasionally observed in the few deep boreholes into the Heligoland-Pomerania Deformation Belt, in southern Denmark, NE Germany and NW Poland, with scant available indirect data in between indicating only Proterozoic basement and no Caledonian deformation. For Far Eastern Avalonia a similar palaeogeographical history is postulated as Avalonia, with rifting from Gondwana in Arenig or earlier times, collision with Baltica before the mid-Ashgill and deformation between the late Ordovician and latest Silurian. The Avalonia concept might need to be expanded to an ‘Avalonian Terrane Assemblage’ with cratonic cores and small short-lived oceans as in the Armorican Terrane Assemblage.

Most of the sulfide produced in surface marine sediments is eventually oxidized back to sulfate via sulfur compounds of intermediate oxidation state in a complex web of competing chemical and biological reactions. Improved handling, derivatization, and chromatographic techniques allowed us to more closely examine the occurrence and fate of the sulfur intermediates elemental sulfur (S 0), thiosulfate (S 2 O 3 2−), tetrathionate (S 4 O 6 2−), and sulfite (SO 3 2−) in Black Sea and North Sea sediments. Elemental sulfur was the most abundant sulfur intermediate with concentrations ∼3 orders of magnitude higher than the dissolved species, which were typically in the low micromolar range or below. Turnover times of the intermediate sulfur compounds were inversely correlated with concentration and followed the order: SO 3 2− ≈ S 4 O 6 2− > S 2 O 3 2− > S 0 . Experiments with anoxic but non-sulfidic surface sediments from the Black Sea revealed that added sulfide and sulfite disappeared most rapidly, followed by thiosulfate. Competing chemical reactions, including the reaction of sulfite with sedimentary S 0 that led to temporarily increased thiosulfate concentrations, resulted in the rapid disappearance of SO 3 2− . Conversely, low thiosulfate concentrations in the Black Sea sediments (<3µM) were attributed to the activity of thiosulfate-consuming bacteria. Experiments with anoxic but non-sulfidic sediments revealed that 1 mol of tetrathionate was rapidly converted to 2 moles of thiosulfate. This tetrathionate reduction was bacterially mediated and occurred generally much faster than thiosulfate consumption. The rapid reduction of tetrathionate back to thiosulfate creates a cul-de-sac in the sulfur cycle, with thiosulfate acting as a bottleneck for the oxidation pathways between sulfide and sulfate.