Depositional environments within Middle Jurassic oyster-dominated lagoons: an integrated litho-, bio- and palynofacies study of the Duntulm Formation (Great Estuarine Group, Inner Hebrides)

1990 ◽  
Vol 81 (1) ◽  
pp. 1-22 ◽  
Author(s):  
Julian E. Andrews ◽  
William Walton
Keyword(s):  
Middle Jurassic ◽  
Depositional Environments ◽  
Thickness Variation ◽  
Freshwater Molluscs ◽  
Planktonic Alga ◽  
Pollen And Spores ◽  
Sandstone Formation ◽  
Strong Control ◽  
Structural High

ABSTRACTThe Duntulm Formation of the Bathonian (Middle Jurassic) Great Estuarine Group represents a marine-brackish lagoonal complex which was transgressively established on the drowned delta of the underlying Valtos Sandstone Formation. Duntulm Formation sediments accumulated in adjacent basins, the Sea of the Hebrides-and Inner Hebrides-basins. Litho-, bio-, and palynofacies analysis of these rocks show that the most distinctive lithologies, monotypic shell banks of the oyster Praeexogyra hebridica (Lithofacies 1), accumulated under variable, but distinctly marine conditions. Argillaceous carbonate muds (Lithofacies 2), probably accumulated in the lee of the oyster banks under variably marine-freshwater conditions, while the supralittoral lagoon shores were fringed by algal marshes (Lithofacies 3). The palynology of Lithofacies 3 shows that some marshes accumulated close to the lagoon (dominated by marine dinocysts), while others formed further inland (dominated by terrestrial pollen and spores). In the N of the Sea of the Hebrides Basin, small deltas continued to prograde into the lagoons (Lithofacies 4), and toward the end of Duntulm Formation times, muds and sands colonised by freshwater molluscs (Unio and Neomiodon), the planktonic alga Botryococcus, and dominated by terrestrial pollen and spores (Lithofacies 5), accumulated in this area, representing a basin-wide change from marine to freshwater conditions. The structural high which divided the basins exerted a strong control on lithofacies evolution, effectively preventing any material coarser than silt grade entering the Inner Hebrides Basin. Thickness variation in the Formation is similarly structurally/facies linked, with thick sequences accumulating where sandstones (Lithofacies 4) predominate, and thin sequences occurring close to the structural high.

scholarly journals New data on Callovian (Middle Jurassic) belemnites and palynomorphs from the Northern Caucasus, southwest Russia

Geologos ◽  
2016 ◽  
Vol 22 (1) ◽  
pp. 49-59 ◽  
Author(s):  
Oksana S. Dzyuba ◽  
Anna A. Goryacheva ◽  
Dmitry A. Ruban ◽  
Victoria V. Gnezdilova ◽  
Pavel P. Zayats
Keyword(s):  
Middle Jurassic ◽  
Large Scale ◽  
Field Studies ◽  
Northern Caucasus ◽  
The Caucasus ◽  
Stratotype Section ◽  
Pollen And Spores ◽  
Degree Of Condensation ◽  
Northern Tethyan Margin ◽  
The Town

Abstract Palaeontological data on the Caucasus are highly important for large-scale stratigraphical and palaeobiogeographical assessment of the northern Tethyan margin, but this information is often scarce and not available in English. Field studies in the Northern Caucasus have now permitted to amass some new data. Two belemnite species are described from the stratotype section of the Kamennomostskaja Formation (Callovian, Middle Jurassic) near the town of Kamennomostskij in Adygeja (Northern Caucasus). These are Belemnopsis subhastata (von Zieten, 1831) and Rhopaloteuthis ominosa Gustomesov, 1968. The latter is a rare species, and the present find allows new insights into its taxonomy. A palyno-logical analysis of the belemnite-bearing sample was carried out, and a diverse assemblage of dinocysts, acritarchs and prasinophytes, plus pollen and spores recognised. The most abundant palynomorphs are Micrhystridium and Classopollis. Data on belemnites coupled with those on palynomorphs indicate the early Callovian age of the sample level. This interpretation differs slightly from previous conclusions based on ammonites and dinocysts. If this age is correct, the degree of condensation of Callovian deposits in the section studied was lesser than previously assumed.

scholarly journals Study on the Strata Movement Rule of the Ultrathick and Weak Cementation Overburden in Deep Mining by Similar Material Simulation: A Case Study in China

2020 ◽  
Vol 2020 ◽  
pp. 1-21 ◽  
Author(s):  
Guojian Zhang ◽  
Guangli Guo ◽  
Yi’nan Lv ◽  
Yaqiang Gong
Keyword(s):  
Material Model ◽  
Failure Pattern ◽  
Central China ◽  
Western China ◽  
Scale Transformation ◽  
Similar Material ◽  
Deep Mining ◽  
Mining Areas ◽  
Sandstone Formation ◽  
Strong Control

In the deep mining areas of western China, there exist ultrathick and weak cementation strata in the overburdens above the Jurassic coal seams, and the overburden lithology is generally moderately a little weaker than the medium-hard strata. Yet, the practical measurement indicates that the surface movement rule in this area displays the specialty that is apparently inconsistent with its lithology, which increases the uncertainty of safe production in coal mines. In this study, the similar material and numerical simulations were conducted to investigate the movement rule and failure pattern of the ultrathick and weak cementation overburden. In addition, the photographing scale transformation-time baseline parallax (PST-TBP) method was used to monitor the similar material model to makeup for the lacks of Xi'an Jiaotong University Digital Close-range Industrial Photogrammetry System (XJTUDP) software. The findings of this study can be summarized as follows. (1) To some extent, the PST-TBP method can makeup for the deficiency of the XJTUDP software because the measurement accuracy of the PST-TBP method is 0.47 mm. (2) The height of the caving zone is approximately 66 m, and the height of the water suture zone is about 112 m, which is obviously larger than that of the medium-hard and soft overburden in eastern-central China. (3) The first breaking span of the immediate roof reaches 120 m, the cyclic fracturing length is about 60 m, and the separation occurred at 43 m and 66 m above the coal seam. (4) The failure pattern of the ultrathick and weak cementation overburden is “beam-arch shell,” and the failure boundary is arch. (5) The Zhidan group sandstone and Jurassic sandstone formations have strong control effects. The Zhidan group sandstone is the main control stratum and the Jurassic sandstone formation is the secondary-control stratum. The research results provide an insight into guiding the safe mining of deep coal in the ultrathick and weak cementation overburden.

Compositions, sources and depositional environments of organic matter from the Middle Jurassic clays of Poland

2007 ◽  
Vol 22 (11) ◽  
pp. 2456-2485 ◽  
Author(s):  
Leszek Marynowski ◽  
Michał Zatoń ◽  
Bernd R.T. Simoneit ◽  
Angelika Otto ◽  
Mariusz O. Jędrysek ◽  
...  
Keyword(s):  
Organic Matter ◽  
Middle Jurassic ◽  
Depositional Environments

scholarly journals First dinosaur from the Isle of Eigg (Valtos Sandstone Formation, Middle Jurassic), Scotland

2020 ◽  
pp. 1-16
Author(s):  
Elsa PANCIROLI ◽  
Gregory F. FUNSTON ◽  
Femke HOLWERDA ◽  
Susannah C. R. MAIDMENT ◽  
Davide FOFFA ◽  
...  
Keyword(s):  
Middle Jurassic ◽  
Diagnostic Features ◽  
Cross Sectional ◽  
Limb Bones ◽  
Fossil Material ◽  
Sandstone Formation ◽  
Dinosaur Fossil ◽  
High Degree ◽  
Body Fossil ◽  
Isle Of Skye

ABSTRACT Dinosaur body fossil material is rare in Scotland, previously known almost exclusively from the Great Estuarine Group on the Isle of Skye. We report the first unequivocal dinosaur fossil from the Isle of Eigg, belonging to a Bathonian (Middle Jurassic) taxon of uncertain affinity. The limb bone NMS G.2020.10.1 is incomplete, but through a combination of anatomical comparison and osteohistology, we determine it most likely represents a stegosaur fibula. The overall proportions and cross-sectional geometry are similar to the fibulae of thyreophorans. Examination of the bone microstructure reveals a high degree of remodelling and randomly distributed longitudinal canals in the remaining primary cortical bone. This contrasts with the histological signal expected of theropod or sauropod limb bones, but is consistent with previous studies of thyreophorans, specifically stegosaurs. Previous dinosaur material from Skye and broadly contemporaneous sites in England belongs to this group, including Loricatosaurus and Sarcolestes and a number of indeterminate stegosaur specimens. Theropods such as Megalosaurus and sauropods such as Cetiosaurus are also known from these localities. Although we find strong evidence for a stegosaur affinity, diagnostic features are not observed on NMS G.2020.10.1, preventing us from referring it to any known genera. The presence of this large-bodied stegosaur on Eigg adds a significant new datapoint for dinosaur distribution in the Middle Jurassic of Scotland.

Depositional environments of a Middle Jurassic terrestrial vertebrate assemblage, Huizachal Canyon, Mexico

1995 ◽  
Vol 15 (3) ◽  
pp. 561-575 ◽  
Author(s):  
D. E. Fastovsky ◽  
J. M. Clark ◽  
N. H. Strater ◽  
M. Montellano ◽  
R. Hernandez R. ◽  
...  
Keyword(s):  
Middle Jurassic ◽  
Depositional Environments ◽  
Terrestrial Vertebrate ◽  
Vertebrate Assemblage

scholarly journals Sedimentology and depositional environments of Murihiku Supergroup sediments exposed in the Southland Syncline, New Zealand: Implications for reservoir potential in the Great South Basin

2021 ◽  
Author(s):  
◽  
Angus David Howden
Keyword(s):  
New Zealand ◽  
Middle Jurassic ◽  
Petroleum Industry ◽  
Depositional Environments ◽  
Seismic Facies ◽  
Late Triassic ◽  
Petrographic Composition ◽  
South Basin ◽  
Porosity And Permeability ◽  
Reservoir Potential

<p>A considerable amount is known about the biostratigraphy and organic geochemistry of the Murihiku Supergroup sediments exposed in coastal outcrops of the Southland Syncline, New Zealand. Much less work has been undertaken on the sedimentology of these strata, or understanding their depositional environments and depositional trends through time. What these implications are for reservoir prospectivity in the adjacent Great South Basin, has also had little study focused on it.  This thesis addresses these issues by undertaking outcrop-based sedimentological and facies interpretations of these rocks, thin-section based petrographic composition and provenance analysis, augmented by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM), as well as porosity and permeability measurements from outcrop core plugs. Petroleum industry seismic data has additionally enabled seismic facies mapping of Murihiku rocks in the offshore Great South Basin.  Outcrop observations point to a progressive change in depositional setting, from shelf / upper slope settings during the Late Triassic, to base of slope turbidite deposition in the Early Jurassic. This transgression is followed by regression into fluvial settings in the youngest outcropping Murihiku rocks in the study of Middle Jurassic age. Petrographically the sandstones are feldspathic and lithic arenites and feldspathic and lithic wackes. Provenance suggests derivation from an evolving, intermediate arc that was becoming more siliceous through Late Triassic and Middle Jurassic time. Diagenesis is characterised by early calcite and chlorite precipitation which have almost completely destroyed any primary porosity. Any secondary micro porosity has subsequently been infilled through dissolution of framework grains and zeolitization. SEM and core plug porosity and permeability measurements corroborate the diagenetic changes observed petrographically, with only fluvial facies of Middle Jurassic (Upper Temaikan) age showing any measureable porosity or permeability.  As a result, reservoir potential for the Late Triassic to Middle Jurassic, Murihiku Supergroup rocks analysed in this study is low. Younger Murihiku sandstones which are postulated to occur offshore in the Great South Basin are likely to be less influenced by burial diagenesis. As shown from North Island occurrences, these younger successions hold some potential.The reservoir potential for these youngest portions of the Murihiku succession therefore remains positive, both in the Great South Basin, as well as other frontier areas of Zealandia, and continue to provide an exploration target for the petroleum industry.</p>

scholarly journals The Jurassic of East Greenland: a sedimentary record of thermal subsidence, onset and culmination of rifting

2003 ◽  
Vol 1 ◽  
pp. 657-722 ◽  
Author(s):  
Finn Surlyk
Keyword(s):  
North Sea ◽  
Middle Jurassic ◽  
Sedimentary Facies ◽  
Lower Triassic ◽  
Depositional Environments ◽  
The Arctic ◽  
Time Interval ◽  
East Greenland ◽  
Thermal Subsidence

The Late Palaeozoic – Mesozoic extensional basin complex of East Greenland contains a record of deposition during a period of Rhaetian – Early Bajocian thermal subsidence, the onset of rifting in the Late Bajocian, its growth during the Bathonian–Kimmeridgian, culmination of rifting in the Volgian – Early Ryazanian, and waning in the Late Ryazanian – Hauterivian. The area was centred over a palaeolatitude of about 45°N in the Rhaetian and drifted northwards to about 50°N in the Hauterivian. A major climate change from arid to humid subtropical conditions took place at the Norian–Rhaetian transition. Deposition was in addition governed by a long-term sea-level rise with highstands in the Toarcian–Aalenian, latest Callovian and Kimmeridgian, and lowstands in the latest Bajocian – earliest Bathonian, Middle Oxfordian and Volgian. The Rhaetian – Lower Bajocian succession is considered the upper part of a megasequence, termed J1, with its base in the upper Lower Triassic, whereas the Upper Bajocian – Hauterivian succession forms a complete, syn-rift megasequence, termed J2. The southern part of the basin complex in Jameson Land contains a relatively complete Rhaetian–Ryazanian succession and underwent only minor tilting during Middle Jurassic – earliest Cretaceous rifting. Rhaetian – Lower Jurassic deposits are absent north of Jameson Land and this region was fragmented into strongly tilted fault blocks during the protracted rift event. The syn-rift successions of the two areas accordingly show different long-term trends in sedimentary facies. In the southern area, the J2 syn-rift megasequence forms a symmetrical regressive–transgressive–regressive cycle, whereas the J2 megasequence in the northern area shows an asymmetrical, stepwise deepening trend. A total of eight tectonostratigraphic sequences are recognised in the Rhaetian–Hauterivian interval. They reflect major changes in basin configuration, drainage systems, sediment transport and distribution patterns, and in facies and depositional environments. The sequences are bounded by regional unconformities or flooding surfaces and have average durations in the order of 10 Ma. They are subdivided into conventional unconformity-bounded depositional sequences with durations ranging from tens of thousands of years, in the Milankovitch frequency band, up to several million years. Deposition was alluvial and lacustrine in the Rhaetian–Sinemurian, but almost exclusively marine during the Pliensbachian–Hauterivian time interval when a marine strait, up to 500 km wide and more than 2000 km long, developed between Greenland and Norway, connecting the Arctic Sea and the North Sea. Coal-bearing fluvial and paralic deposits occur, however, at the base of the onlapping Middle Jurassic succession in the central and northern part of the basin complex. The sedimentary development is similar to that in the Northern North Sea and on the Norwegian shelf, and East Greenland offers important onshore analogues for virtually all of the types of deeply buried Jurassic depositional systems of these areas and especially their hydrocarbon reservoirs.

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