The spatial and temporal distribution of diagenetic alterations in siliciclastic sequences is controlled by a complex array of interrelated parameters that prevail during eodiagenesis, mesodiagenesis and telodiagenesis. The spatial distribution of near-su

Spatial and temporal distribution of diagenetic alterations in siliciclastic rocks: implications for mass transfer in sedimentary basins

Palaeoecology and evolution of marine hard substrate communities

Carbon cycling at ancient methane-seeps

Large igneous provinces (LIPs) are intraplate magmatic events, involving volumes of mainly mafic magma upwards of 100,000 km3, and often above 1 million km3. They are linked to continental break-up, global environmental catastrophes, regional uplift and a variety of ore deposit types. In this up-to-date, fascinating book, leading expert Richard E. Ernst explores all aspects of LIPs, beginning by introducing their definition and essential characteristics. Topics covered include continental and oceanic LIPs; their origins, structures, and geochemistry; geological and environmental effects; association with silicic, carbonatite and kimberlite magmatism; and analogues of LIPs in the Archean, and on other planets. The book concludes with an assessment of LIPs' influence on natural resources such as mineral deposits, petroleum and aquifers. This is a one-stop resource for researchers and graduate students in a wide range of disciplines, including tectonics, igneous petrology, geochemistry, geophysics, Earth history, and planetary geology, and for mining industry professionals.

Large Igneous Provinces

Hydrocarbon seep and hydrothermal vent paleoenvironments and paleontology: Past developments and future research directions

Some pockmarks on the Norwegian continental shelf contain patches of cemented sediment that can provide hardgrounds attractive to a variety of benthonic organisms. Detailed examination of a sandstone sample from a pockmark in Norwegian Block 25/7 in the North Sea has revealed the presence of Mg calcite and aragonite cements, some of the latter forming botryoids. All cement types are characterized by extremely light carbon isotopic compositions, with a mean 13C value of -56.1 PDB, which shows that the cements contain carbonate produced by oxidation of biogenic methane. Oxidation occurred in both the oxic and anoxic diagenetic zones. Trace amounts of interstitial methane (mean 13C = -40.8%) and higher hydrocarbon gases (up to C5) with a C1/Cn ratio of 0.855-0.874 in the pockmark sediments indicate that some thermogenic methane may be mixed with the biogenic gas.

Methane-related carbonate cements in pockmarks of the North Sea

The Oslo Rift is the northernmost part of the Rotliegendes basin system in Europe. The rift was formed by lithospheric stretching north of the Tornquist fault system and is related tectonically and in time to the last phase of the Variscan orogeny. The main graben forming period in the Oslo Region began in Late Carboniferous, culminating some 20-30 Ma later with extensive volcanism and rifting, and later with uplift and emplacement of major batholiths. It ended with a final termination of intrusions in the Early Triassic, some 65 Ma after the tectonic and magmatic onset. We divide the geological development of the rift into six stages. Sediments, even with marine incursions occur exclusively during the forerunner to rifting. The magmatic products in the Oslo Rift vary in composition and are unevenly distributed through the six stages along the length of the structure.

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The Permo-Carboniferous Oslo Rift through Six Stages and 65 Million Years

The Permo-Carboniferous Oslo Rift, an en echelon graben system, was created by east-west extension partly caused by dextral movement along the Sorgenfrei-Tornquist-Teissure Zone. This zone was most likely activated by a late compressional event in the Variscan segment of the Hercynian Orogenic cycle. The Oslo Rift is thus an example of local suturation during the creation of the Pangea super-continent. The north-south trending Oslo Rift system consists of the onshore Oslo Graben and the offshore Skagerrak Graben. The basin-fill of the onshore Oslo Graben is characterised by large volumes of volcanics and only minor sedimentary rocks, for which a six phase development model from pre-rift to the termination phase has been derived. The pre-rift and initial rift phases (Late Carboniferous) coincided with the late Variscan stage of the Hercynian Orogeny. The basin fill which accumulated prior to the rift basin formation, the pre-rift phase, consists of a thin alluvial and deltaic succession with a marine limestone of (?) Moscovian age. The initial rift phase is recorded in the Vestfold Graben with more than 1500 m of alkali basalt lavas, while in the north, close to the transfer zone in the initial Oslo Graben, the basin fill comprises Gzelian lacustrine delta and volcaniclastic alluvial fan deposits capped by a single tholeiitic basalt. The synrift phase (Early Permian) is divided into two sub-phases that were characterized by plateau lavas, fissure eruption and normal faulting as well as formation of central volcanos and caldera collapse. The basin fill in the syn-rift phase, besides volcanics and thin but widespread continental deposits that are intercalated with the plateau lavas, developed as thick alluvial fan deposits along the master fault or locally inside the rift valley along escarpments bounding a volcanic accommodation zone, and as thick eolian and wadi deposits in the northern part of the Oslo Graben. The two last recorded phases (late Early and Late Permian) of graben development were the emplacement of young syenitic and granitic batholiths. The highly volcanic Oslo Rift is comparable with the Kenya Rift of the East African rifts and has some similarities to the Rio Grande Rift. In many periods the high production rate of extrusives in the Oslo Graben was enough to fill the relief created by extension, thus explaining the small amount of syn-rift sediments. Although only known from seismic and geophysical data, the basin-fill development of the offshore Skagerrak Graben is similar to the Oslo Graben, but probably with less volcanism. A post-rift sedimentary cover as a response to thermal cooling has probably been developed in the offshore Skagerrak Graben. A previous existence of post-rift basin fill in the onshore Oslo Graben is unclear. Post-rift sediments may also have been developed there, but at different scale and time in comparison to the Skagerrak Graben due to variations in duration and activity of the magmatism. The assumed post-rift infill is dated as Late Permian (offshore graben) and Triassic/ Early Jurassic (onshore graben) by onshore age determination and by seismic/well correlation between neighbouring basins. Subsequent uplift and erosion of the Oslo Rift and surrounding areas are suggested to have occurred in Early Triassic and “mid” Jurassic, with stripping of the post-rift basin fill in the offshore Skagerrak Graben taking place in Early Triassic, whereas “mid” Jurassic uplift removed the possible post-rift basin fill and much of the syn-rift basin fill of the onshore Oslo Graben. Potential source rocks are burned out in the Oslo Graben. However the Skagerrak Graben may yet prove to be hydrocarbon bearing.

The Upper Carboniferous-Permian Oslo Rift; Basin Fill in Relation to Tectonic Development

The small island of Bjørnøya (\"Bear Island\"), situated in the Barents Sea almost midway between northern Norway and Spitsbergen, displays a Precambrian to Triassic succession in a continuous series of spectacular cliff exposures. These exposures provide a key not only to the evolution of the Stappen High (on which Bjørnøya rests) but also to the development of analogous structures along the major lineaments that subsequently contributed to the formation of both the Norwegian-Greenland Sea and the Arctic Ocean. Precambrian to Ordovician dolomites, limestones, quartzites and shales form the basement on which the Upper Palaeozoic succession of Bjørnøya was deposited. In latest Devonian and early Carboniferous times the area subsided asymmetrically, probably in response to NE-SW extension; a southwestwards downtilted half-graben developed over the present-day island, with the basinal axis dipping gently NNW. Some 600 m of sandstones, coals and shales are preserved in two upward coarsening sequences. These represent the repeated progradations of sandy fan systems over floodplains with lakes and northward meandering river channels. Mid-Carboniferous (Serpukhovian) uplift was followed by renewed rifting and the same western hinterland again shed debris over its faulted eastern margins. A shift from humid to a semi-arid climate is reflected by the predominantly red colouration of the resultant 200 m thick succession of conglomerates, sandstones and shales, with caliche horizons. Penecontemporaneous regional sea level rise resulted in the gradual replacement of the alluvial floodbasin deposits by shallow marine siliciclastics and carbonates of shoreline, tidal flat and shallow shelf origin. Continued transgression through the Moscovian, perhaps also with decreasing subsidence rates and only intermittent tectonism, is indicated by the gradual change to a marine carbonate-dominated succession, with cherty biomicrites reflecting the establishment of an open carbonate shelf over the entire area. A marked rejuvenation of tectonic activity in the late Moscovian established a different depositional mosaic faulting affected exposures on the present island along N-S to NE-SW lineaments, with differential subsidence down to the west. This produced erosion of earlier deposits over the eastern part of Bjørnøya and deposition of conglomerates, sandstones, shales and dolomites in alluvial gully, coastal and shallow shelf environments to the west. A 200 m thick succession is preserved in western areas and eroded remnants are also preserved as outliers elsewhere on the island. Conglomerate clasts indicate derivation by successive stripping and redeposition of mid-Carboniferous to uppermost Devonian and then basement strata. By the latest Carboniferous the region had again stabilized and platform carbonate deposition resumed, with the development of paleoaplysinid carbonate build-ups. Early Permian flexuring, uplift and peneplanation followed, probably with some transpressive movements. The highly condensed midto Upper Permian marine succession of mixed siliciclastics and carbonates oversteps all older strata. The StapNORWEGIAN JOURNAL OF GEOLOGY The geological evolution of Bjørnøya 195

The geological evolution of Bjørnøya, Arctic Norway: Implications for the Barents Shelf

Cores from five wells within the eastern part of Troms I contain mineralogically and texturally mature sandstones (generally classified as quartz arenites) deposited on a stable platform during the Middle and Lower Jurassic. Deposition took place under an overall transgressive regime. The delicate balance between sediment input and basin subsidence is exemplified by the development of a very thick tidal flat sequence, the occurrence of phosphate, glauconite and chamosite, and the supermaturity of the sandstones and the lateral extension of the facies. Two different facies associations are distinguished: (1) a coastal plain/tidal flat facies association (Nordmela Fm); (2) a near shore and inner shelf facies association (Sto Fm, which overlies 1). The main reservoir sand bodies are found within the latter association.

Snorre Olaussen

Papers

Methane-related carbonate cements in pockmarks of the North Sea

The Permo-Carboniferous Oslo Rift through Six Stages and 65 Million Years

The Upper Carboniferous-Permian Oslo Rift; Basin Fill in Relation to Tectonic Development

The geological evolution of Bjørnøya, Arctic Norway: Implications for the Barents Shelf

Depositional environment and diagenesis of Jurassic reservoir sandstones in the eastern part of Troms I area