scholarly journals Middle Jurassic – Early Cretaceous rifting of the Danish Central Graben

2003 ◽  
Vol 1 ◽  
pp. 247-264 ◽  
Author(s):  
Jens J. Møller ◽  
Erik S. Rasmussen
Keyword(s):  
Early Cretaceous ◽  
Middle Jurassic ◽  
Upper Jurassic ◽  
Sea Level Changes ◽  
Tectonic Event ◽  
Boundary Fault ◽  
The Third ◽  
Structural Framework ◽  
Reservoir Sandstones ◽  
Sandstone Formation

During the Jurassic – Early Cretaceous, the Danish Central Graben developed as a N–S- to NNW– SSE-trending graben bounded by the Ringkøbing–Fyn High towards the east and the Mid North Sea High towards the west. The graben consists of a system of half-grabens and evolved by faultcontrolled subsidence; three main rift pulses have been recognised. The first pulse ranged from the Callovian to the Early Oxfordian, the second pulse was initiated in the latest Late Kimmeridgian and lasted for most of the Early Volgian, and the third and final pulse occurred within the Ryazanian in the Early Cretaceous. The first pulse was characterised by subsidence along N–S-trending faults. The most pronounced fault-controlled subsidence occurred in the east, especially along N–S-striking segments of the boundary fault to the Ringkøbing–Fyn High. During this period, minor salt movements occurred with the development of salt pillows. The activity along the N–S-trending faults ceased during the Oxfordian. During the second pulse, in Early Volgian times, subsidence was concentrated along new NNW–SSE-trending faults and the main depocentre shifted westward, being most marked within the Tail End Graben, the Arne–Elin Graben, and the Feda Graben. This tectonic event was accompanied by the accumulation of a relatively thick sediment load resulting in the development of salt diapirs, especially within the Salt Dome Province. The third tectonic pulse was essentially a reactivation of the NNW–SSE-trending structures and there is clear evidence of subsidence controlled by faulting and salt movements. Despite the overall extensional tectonic regime, local compressional tectonics resulted in thrusting. For instance, the Gert Ridge is interpreted to have formed by readjustment at the boundary fault between two subsiding blocks. The structural framework during graben evolution controlled, to some degree, the distribution of reservoir sandstones. Reservoir sandstones associated with periods of rotational tilt include Middle Jurassic deposits referred to the Bryne and Lulu Formations, and Upper Jurassic sandstones referred informally to the ‘Fife Sandstone Formation’. Sands deposited during tectonic relaxation are represented by the Heno Formation and Upper Jurassic turbidites interbedded in the Farsund Formation. Sea-level changes were probably most important during periods of tectonic relaxation, particularly with respect to the deposition of lowstand sandstones in basinal areas.

Glendonites from Mesozoic succession of eastern Barents sea: distribution, genesis and paleoclimatic implications

2020 ◽  
Author(s):  
Kseniya Mikhailova ◽  
Victoria Ershova ◽  
Mikhail Rogov ◽  
Boris Pokrovsky ◽  
Oleg Vereshchagin
Keyword(s):  
Organic Matter ◽  
Calcium Carbonate ◽  
Sulfate Reduction ◽  
Early Cretaceous ◽  
Lower Cretaceous ◽  
Middle Jurassic ◽  
Barents Sea ◽  
Upper Jurassic ◽  
Anaerobic Oxidation Of Methane ◽  
Oxidation Of Methane

<p>Glendonites often used as paleoclimate indicator of cold near-bottom temperature, as these are calcite pseudomorphs of ikaite, a metastable calcium carbonate hexahydrate, precipitates mostly under low temperature (mainly from 0-4<sup>o</sup>C) and may be stabilized by high phosphate concentrations that occurs due to anaerobic oxidation of methane and/or organic matter; dissolved organic carbon, sulfates and amino acid may contribute ikaite formation as well.  Therefore, glendonites-bearing host rocks frequently include glacial deposits that make them useful as a paleoclimate indicator of near-freezing temperature.</p><p>Our study is based on material collected from five wells drilled in eastern Barents Sea: Severo-Murmanskaya, Ledovaya – 1,2; Ludlovskaya – 1,2. The studied glendonites, mainly represented by relatively small rhombohedral pseudomorphs (0,5-2 cm) and rarely by stellate aggregates, collected from Middle Jurassic to Lower Cretaceous shallow marine clastic deposits. They scattered distributed throughout succession. Totally 18 samples of glendonites were studied. The age of host-bearing rocks were defined by fossils: bivalves or ammonites, microfossils or dinoflagellate. Bajocian-Bathonian glendonites were collected from Ledovaya – 1 and Ludlovskaya – 1 and 2 wells; in addition to these occurrences Middle Jurassic glendonites are known also in boreholes drilled at Shtockmanovskoe field. Numerous ‘jarrowite-like’ glendonites of the Middle Volgian (~ latest early Tithonian) age were sampled from Severo-Murmanskaya well. Unique Late Barremian glendonites were found in Ledovaya – 2 well.</p><p>δ<sup>18</sup>O values of Middle Jurassic glendonite concretions range from – 5.4 to –1.7 ‰ Vienna Pee Dee Belemnite (VPDB); for Upper Jurassic – Lower Cretaceous δ<sup>18</sup>O values range from – 4.3 to –1.6 ‰ VPDB; for Lower Cretaceous - δ<sup>18</sup>O values range from – 4.5 to –3.4 ‰ VPDB. Carbon isotope composition for Middle Jurassic glendonite concretions δ<sup>13</sup>C values range from – 33.3 to –22.6 ‰ VPDB; for Upper Jurassic – Lower Cretaceous δ<sup>13</sup>C values range from – 25.1 to –18.4 ‰ VPDB; for Lower Cretaceous - δ<sup>13</sup>C values range from – 30.1 to –25.6 ‰ VPDB.</p><p>Based on δ<sup>18</sup>O data we supposed that seawater had a strong influence on ikaite-derived calcite precipitation. Received data coincide with δ<sup>18</sup>O values reported from other Mesozoic glendonites and Quaternary glendonites formed in cold environments. Values of δ<sup>13</sup>C of glendonites are close to bacterial sulfate reduction and/or anaerobic oxidation of methane or organic matter. Glendonites consist of carbonates forming a number of phases which different in phosphorus and magnesium content. Mg-bearing calcium carbonate and dolomite both include framboidal pyrite, which can indicate (1) lack of strong rock transformations activity and (2) presence of sulfate-reduction bacteria in sediments.</p><p>To conclude, Mesozoic climate was generally warm and studied concretions indicate cold climate excursion in Middle Jurassic, Upper Jurassic-Early Cretaceous and Early Cretaceous.</p><p> </p><p>The study was supported by RFBR, project number 20-35-70012.</p>

scholarly journals Warm Middle Jurassic–Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean

2012 ◽  
Vol 8 (1) ◽  
pp. 215-226 ◽  
Author(s):  
H. C. Jenkyns ◽  
L. Schouten-Huibers ◽  
S. Schouten ◽  
J. S. Sinninghe Damsté
Keyword(s):  
Southern Ocean ◽  
Early Cretaceous ◽  
Middle Jurassic ◽  
Warming Trend ◽  
Upper Jurassic ◽  
Climatic Conditions ◽  
Sea Surface ◽  
Polar Regions ◽  
Sea Surface Temperatures ◽  
Surface Temperatures

Abstract. Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed during the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of isotopic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEX86 back to the Middle Jurassic indicates that relatively warm sea-surface conditions (26–30 °C) existed from this interval (∼160 Ma) to the Early Cretaceous (∼115 Ma) in the Southern Ocean, with a general warming trend through the Late Jurassic followed by a general cooling trend through the Early Cretaceous. The lowest sea-surface temperatures are recorded from around the Callovian–Oxfordian boundary, an interval identified in Europe as relatively cool, but do not fall below 25 °C. The early Aptian Oceanic Anoxic Event, identified on the basis of published biostratigraphy, total organic carbon and carbon-isotope stratigraphy, records an interval with the lowest, albeit fluctuating Early Cretaceous palaeotemperatures (∼26 °C), recalling similar phenomena recorded from Europe and the tropical Pacific Ocean. Extant belemnite δ18O data, assuming an isotopic composition of waters inhabited by these fossils of −1‰ SMOW, give palaeotemperatures throughout the Upper Jurassic–Lower Cretaceous interval that are consistently lower by ∼14 °C than does TEX86 and the molluscs likely record conditions below the thermocline. The long-term, warm climatic conditions indicated by the TEX86 data would only be compatible with the existence of continental ice if appreciable areas of high altitude existed on Antarctica, and/or in other polar regions, during the Mesozoic Era.

scholarly journals THE LATE EARLY CRETACEOUS TRANSGRESSION ON THE LATERITES IN VOURINOS AND VERMION MASSIFS (WESTERN MACEDONIA, GREECE)

2018 ◽  
Vol 40 (1) ◽  
pp. 182 ◽  
Author(s):  
A. Photiades ◽  
N. Carras ◽  
V. Bortolotti ◽  
M. Fazzuoli ◽  
G. Principi
Keyword(s):  
Early Cretaceous ◽  
Lower Cretaceous ◽  
Upper Cretaceous ◽  
Carbonate Platform ◽  
Upper Jurassic ◽  
Ophiolite Complex ◽  
Marine Transgression ◽  
The Third ◽  
Normal Salinity

Three stratigraphical sections from eastern Vourinos (Rhodiani area) to eastern Vermion massifs revealed the same age of the latérite events affecting the serpentinized ophiolite complex after its emplacement on the Pelagonian domain. All of them consist from their base upwards of serpentinized harzburgite slivers with lateritic unconformities on the top, followed by transgressive upper Lower Cretaceous neritic limestones. At Kteni locality (Rhodiani area), a laterite horizon, lying on top of serpentinites, is covered by transgressive neritic limestones with Salpingoporella urladanasi, assigning a Barremian - Albian age, followed by Orbitolinidae limestones. At Tsimodia locality (NNW to the previous), the latente horizon, lying on karstified Upper Jurassic reef limestones (which are the top member of a carbonate platform body tectonically lying on the ophiolites), is trans gres s ively overlain by iron-rich pisolith levels and Aptian limestones of the wackes tone-muds tone type, also containing Salpingoporella urladanasi, followed by Cenomanian Orbitolina limestones. Finally, the third examined locality, further north-eastward to the previous, is situated at the eastern slopes of Vermion massif and more precisely at the NWpart of Koumaria village. There, it can again be observed that the lateritized serpentinite slivers are overlain transgress ively by neritic limestones with Salpingoporella urladanasi, passing upwards into Upper Cretaceous recrystallized limestones with Orbitolinidae and rudist fragments and, finally, toflysch deposition. These features allow to recognize that the emersion and the consecutive lateritization of the thrust-emplaced ophiolites in Vourinos and Vermion massifs in the northern Pelagonian domain, starting from the Latest Jurassic, was followed by a marine transgression beginning from the Barremian - Albian, firstly under restricted and brackish carbonate platform conditions, marked by the presence of the dasycladalean alga Salpingoporella urladanasi, followed by normal salinity carbonate platform conditions. The neritic sedimentation was stable until the Early Cenomanian. Subsequently, a deepening, earlier at Vourinos and later at Vermion, resulted in deposition of pelagic and turbiditic carbonates and then offlysch.

scholarly journals Diagenetic impact on reservoir sandstones of the Heno Formation in the Ravn-3 well, Danish Central Graben

2018 ◽  
pp. 9-12
Author(s):  
Simone Pedersen ◽  
Rikke Weibel ◽  
Peter N. Johannessen ◽  
Niels H. Schovsbo
Keyword(s):  
North Sea ◽  
Middle Jurassic ◽  
Oil And Gas ◽  
Mineralogical Composition ◽  
Upper Jurassic ◽  
Gas Production ◽  
Oil And Gas Production ◽  
Carbonate Cement ◽  
Porosity And Permeability ◽  
Reservoir Sandstones

Oil and gas production from siliciclastic reservoirs has hitherto been in the Danish Central Graben mostly from Palaeogene and Middle Jurassic sandstone. The Ravn field was the first Upper Jurassic field to start operation. The reservoir is composed of sandstone of the Heno Formation. Production takes place at a depth of 4000 m, which makes Ravn the deepest producing field in the Danish North Sea. The Heno Formation mainly consists of marine shoreface deposits, where foreshore, middle and lower shoreface sandstones constitute the primary reservoir. The results of this study of the diagenetic impact on the mineralogical composition, porosity and permeability are presented here. Microcrystalline quartz has preserved porosity in the sandstone, whereas illite, quartz overgrowth and carbonate cement have reduced both porosity and permeability.

Sequence stratigraphy of source and reservoir rocks in the Upper Permian and Jurassic of Jameson Land, East Greenland

1998 ◽  
pp. 43-54 ◽  
Author(s):  
Lars Stemmerik ◽  
Gregers Dam ◽  
Nanna Noe-Nygaard ◽  
Stefan Piasecki ◽  
Finn Surlyk
Keyword(s):  
Sequence Stratigraphy ◽  
Middle Jurassic ◽  
Sedimentary Basins ◽  
Upper Jurassic ◽  
Oil Field ◽  
Source Rocks ◽  
Upper Permian ◽  
Shallow Marine ◽  
East Greenland ◽  
Reservoir Rocks

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Stemmerik, L., Dam, G., Noe-Nygaard, N., Piasecki, S., & Surlyk, F. (1998). Sequence stratigraphy of source and reservoir rocks in the Upper Permian and Jurassic of Jameson Land, East Greenland. Geology of Greenland Survey Bulletin, 180, 43-54. https://doi.org/10.34194/ggub.v180.5085 _______________ Approximately half of the hydrocarbons discovered in the North Atlantic petroleum provinces are found in sandstones of latest Triassic – Jurassic age with the Middle Jurassic Brent Group, and its correlatives, being the economically most important reservoir unit accounting for approximately 25% of the reserves. Hydrocarbons in these reservoirs are generated mainly from the Upper Jurassic Kimmeridge Clay and its correlatives with additional contributions from Middle Jurassic coal, Lower Jurassic marine shales and Devonian lacustrine shales. Equivalents to these deeply buried rocks crop out in the well-exposed sedimentary basins of East Greenland where more detailed studies are possible and these basins are frequently used for analogue studies (Fig. 1). Investigations in East Greenland have documented four major organic-rich shale units which are potential source rocks for hydrocarbons. They include marine shales of the Upper Permian Ravnefjeld Formation (Fig. 2), the Middle Jurassic Sortehat Formation and the Upper Jurassic Hareelv Formation (Fig. 4) and lacustrine shales of the uppermost Triassic – lowermost Jurassic Kap Stewart Group (Fig. 3; Surlyk et al. 1986b; Dam & Christiansen 1990; Christiansen et al. 1992, 1993; Dam et al. 1995; Krabbe 1996). Potential reservoir units include Upper Permian shallow marine platform and build-up carbonates of the Wegener Halvø Formation, lacustrine sandstones of the Rhaetian–Sinemurian Kap Stewart Group and marine sandstones of the Pliensbachian–Aalenian Neill Klinter Group, the Upper Bajocian – Callovian Pelion Formation and Upper Oxfordian – Kimmeridgian Hareelv Formation (Figs 2–4; Christiansen et al. 1992). The Jurassic sandstones of Jameson Land are well known as excellent analogues for hydrocarbon reservoirs in the northern North Sea and offshore mid-Norway. The best documented examples are the turbidite sands of the Hareelv Formation as an analogue for the Magnus oil field and the many Paleogene oil and gas fields, the shallow marine Pelion Formation as an analogue for the Brent Group in the Viking Graben and correlative Garn Group of the Norwegian Shelf, the Neill Klinter Group as an analogue for the Tilje, Ror, Ile and Not Formations and the Kap Stewart Group for the Åre Formation (Surlyk 1987, 1991; Dam & Surlyk 1995; Dam et al. 1995; Surlyk & Noe-Nygaard 1995; Engkilde & Surlyk in press). The presence of pre-Late Jurassic source rocks in Jameson Land suggests the presence of correlative source rocks offshore mid-Norway where the Upper Jurassic source rocks are not sufficiently deeply buried to generate hydrocarbons. The Upper Permian Ravnefjeld Formation in particular provides a useful source rock analogue both there and in more distant areas such as the Barents Sea. The present paper is a summary of a research project supported by the Danish Ministry of Environment and Energy (Piasecki et al. 1994). The aim of the project is to improve our understanding of the distribution of source and reservoir rocks by the application of sequence stratigraphy to the basin analysis. We have focused on the Upper Permian and uppermost Triassic– Jurassic successions where the presence of source and reservoir rocks are well documented from previous studies. Field work during the summer of 1993 included biostratigraphic, sedimentological and sequence stratigraphic studies of selected time slices and was supplemented by drilling of 11 shallow cores (Piasecki et al. 1994). The results so far arising from this work are collected in Piasecki et al. (1997), and the present summary highlights the petroleum-related implications.

scholarly journals Jaws of a large belemnite and an ammonite from the Aalenian (Middle Jurassic) of Switzerland

2020 ◽  
Vol 139 (1) ◽  
Author(s):  
Christian Klug ◽  
Walter Etter ◽  
René Hoffmann ◽  
Dirk Fuchs ◽  
Kenneth De Baets
Keyword(s):  
Middle Jurassic ◽  
Opalinus Clay ◽  
Northern Switzerland ◽  
The Third ◽  
Large Size ◽  
Upper Jaw ◽  
Rule Out

AbstractAlthough belemnite rostra can be quite abundant in Jurassic and Cretaceous strata, the record of belemnite jaws was limited to a few specimens from Germany and Russia. Here, we describe and figure three cephalopod jaws from the Middle Jurassic Opalinus Clay of northern Switzerland. Although flattened, the carbonaceous fossils display enough morphological information to rule out an ammonoid, nautiloid or octobrachian origin of the two larger jaws. Their similarities to belemnite jaws from Germany and Russia conforms with our interpretation of these specimens as belemnite jaws. Based on their rather large size, we tentatively assign these two jaws to the megateuthidid Acrocoelites conoideus. The third jaw is a rather small upper jaw of an ammonoid. Since Leioceras opalinum is by far the most common ammonite in this unit in northern Switzerland, we tentatively suggest that the upper jaw belongs to this species.

Modes of extinction, pseudo-extinction and distribution in Middle Jurassic ammonites: terminology

2001 ◽  
Vol 38 (2) ◽  
pp. 187-195
Author(s):  
Gerd EG Westermann
Keyword(s):  
New Species ◽  
Sea Level ◽  
Middle Jurassic ◽  
Small Populations ◽  
Sea Level Changes ◽  
Range Contraction ◽  
Extreme Form ◽  
Phylogenetic Lineage

Mid-Jurassic Ammonitina (Cephalopoda, Mollusca) provide good examples of true and apparent "extinctions" (i.e., taxon or clade disappearances) at the local, regional, and global scales. A terminology is presented. Extinction is the termination of a phylogenetic lineage or entire clade (not of local demes or regional populations). Extinction was often preceded by progressive range contraction that resulted in diachronous regional disappearance ("extirpation") and occurred with the elimination of the last refuge. Other range contractions, however, were not terminal, but were followed by renewed expansions, resulting in temporary absence of the lineage over part of its known range only, due to pseudo-extinction. Some lineages, called Lazarus taxa, apparently disappeared entirely for short or extended periods by pseudotermination (causing a "phylogenetic hiatus"). This is an extreme form of pseudo-extinction with unknown refuge due to small size and (or) unsuitable facies and location. Lineage or clade reappearance may be in the form of new species, whose relationship to ancestral taxa has been problematic. Some disappearances can be explained with displacive competition, where the replacement taxon is either of endemic origin or an immigrant. Recent research in previously underexplored field areas has closed some of the gaps of documentation by finding the refuges. Range contractions and expansions, together with their regional disappearances and pseudo-extinctions, including pseudotermination, were often causally related to sea-level changes, especially eustasy. Most true extinctions, however, cannot be identified precisely, because they occurred in small populations and (or) refuges. Extinctions presumably did not coincide with global geoevents.

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