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Morphological change of Late Permian Radiolaria as seen in pelagic chert sequences
Published in Wang Naiwen, J. Remane, Stratigraphy, 2020
The Permian paleogeography is characterized by the presence of supercontinent Pangea, Panthalassa and Tethys Seas [e.g. 7, 13]. Barron and Fawcett [1] reviewed the climate simulations of the Permian, and the surface circulations of the oceans were also predicted as similar to the present-day Pacific. It was characterized the easterly currents at the lower latitudes. Under such situations, the bedded chert in the Mino Belt were formed successively in the pelagic condition in the Panthalassa. Paleomagnetic study of Triassic bedded chert at the Inuyama area shows that the chert sequences were formed in low latitudes [14]. The paleolatitude of Upper Permian chert also may indicate low latitudes. In Permian time, some seamounts were scattered in the ocean where bedded chert was deposited in the Mino belt. According to Sano [e.g. 12], limestone breccia as talus deposit is distributed around shallow marine sediments on the seamounts. The current system around the seamount might be complicated, producing large, regional differences in environment. There are some intercalations of siliceous claystone, dolomitic chert, and hematite nodules and lenses in the Upper Permian bedded chert in the Mino Belt. Their occurrences are variable in the stratigraphic horizons, suggesting regional differences in depositional environment.
Seismic and geological characteristics of Devonian and Carboniferous deposits in the southwest of the Tomsk region
Published in Vladimir Litvinenko, Topical Issues of Rational Use of Natural Resources 2019, 2019
In early Devonian, a carbonate platform was formed in the study area This is evidenced by shallow marine limestone and biomorphic dolomite, exposed at the North-Ostanin area. The oil pool discovered by the wells #3, #5, #7 is confined to these deposits. The reservoir is of a fractured cavernous-pore type. As notice the lithologists (Yezhova, 2007) void space is provided by caverns. According to the core description, the dolomitization degree of rocks decreases from well #3 to well #5. In the well #14 deposites are represented by another rock type - clay limestone, which is likely to have been formed in deeper marine conditions. The North-Ostanin pool (wells #3, #5, #7) is confined to the anticline slope, which is not intensively fractured and the dolomites are cropped out the erosion surface. In dry wells (2, 8, 9, 12) the limestone is covered with thick breccia.
Sediments and Sedimentary Rocks
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
When marine animals or plants die, their constituent soft tissues rapidly decompose and disappear. Waves, flowing water, or scavenging animals then break hard parts such as shells or bones into small pieces, producing clastic material composed of hard remnants of once-living organisms. These sediments are biochemical sediments that may become biochemical rocks. Biochemical limestone, for example, which forms in shallow marine environments, is produced from skeletal parts and shells made of calcite (calcium carbonate). Such limestones may contain easily seen fossils, but sometimes mechanical weathering breaks shells and other organic debris into such fine material that fossils are unrecognizable. Additionally, recrystallization during lithification may cause fossil material to combine and become part of larger mineral grains, thus removing the fossils altogether.
Lituitid cephalopods from the upper Darriwilian and basal Sandbian (Middle–Upper Ordovician) of Estonia
Published in GFF, 2020
Martina Aubrechtová, Tõnu Meidla
The Ordovician limestone succession in Estonia and adjacent areas begins with Dapingian cool-water carbonates deposited on a shallow, marine, sediment-starving ramp (Meidla et al. 2014). Most of the fossil cephalopods studied herein come from the strata of the Darriwilian age (Fig. 3) which comprise three depositional sequences as detailed by Ainsaar et al. (2007). Throughout the Middle and Late Ordovician, gradual changes in the type of sedimentation and biofacies led to the appearance of tropical carbonates in the early Katian. The changes are ascribed to the gradual climatic change resulting from the northward drift of the Baltica Palaeocontinent from the temperate climatic zone to the (sub-)tropical realm (Nestor & Einasto 1997; see also Fig. 2 herein). Although some increase of sedimentation rates through the Middle Ordovician suggests increasing carbonate production rates, the formation of the earliest Late Ordovician strata still took place in a relatively cool-water marine basin located at intermediate southern latitudes. The Middle and lowermost Upper Ordovician succession in northern Estonia is composed of limestones containing some intercalations of kukersite oil shale that are mainly confined to the Kukruse Regional Stage, basal Upper Ordovician.
Tectonic cycles of the New England Orogen, eastern Australia: A Review
Published in Australian Journal of Earth Sciences, 2019
K. Jessop, N. R. Daczko, S. Piazolo
The forearc basin was largely marine in the early Carboniferous but became progressively continental as the arc developed until, from about 315 Ma, it was entirely continental (e.g. Roberts et al.,2006). Facies in the Tamworth Belt of the SNEO range from marginal continental in the west to shallow and deeper marine to the east (Champion, 2016). McPhie (1987) documented continental conglomerate layers interbedded with silicic ignimbrite layers along the western margin of the belt. To the east, limestone, and shallow marine sedimentary rocks and tuffs derived from the arc occur. Similar shallow marine to continental facies are recorded in the forearc basin rocks of the Yarrol Province in the NNEO, with oolitic limestones commonly found in the lower to mid Carboniferous Rockhampton Group and terrestrial conditions prevailing during late Carboniferous deposition of the Youlambie Conglomerate (Blake & Withnall, 2013).
Hydrothermal alteration, lithogeochemical marker units and vectors towards mineralisation at the Svärdsjö Zn-Pb-Cu deposit, Bergslagen, Sweden
Published in GFF, 2022
Anton Fahlvik, Tobias C. Kampmann, Nils F. Jansson
Metasedimentary units dominated by metaturbidite, metagreywacke and quartzite constitute the lowermost stratigraphic unit of the BLU and mark the early stage of the Svecokarelian orogeny (Stephens et al. 2009). The metasedimentary rocks stratigraphically underlie a 1–8 km thick, felsic metavolcanic unit of predominantly rhyolitic composition. Facies analysis has shown that this metavolcanic unit is dominated by volcaniclastic deposits including massive pumice breccia, normal-graded pumice-lithic breccia, crystal-rich volcanic sandstone and ash-rich volcanic siltstone. These have been attributed to a predominately shallow marine volcanic environment in the BLU at c. 1.91–1.89 Ga, in which intense volcanism was related to a system of nested calderas (Allen et al. 1996). Proximal to volcanic centres, commonly porphyritic subvolcanic intrusions of mainly felsic composition were emplaced into the volcaniclastic succession (Allen et al. 1996). The shallow marine setting of the sequence has been inferred through the identification of stromatolitic textures in marble interbeds, and evidence of reworking (e.g., cross-bedding) in metamorphosed volcaniclastic deposits. Subsidence during the waning stages of volcanism facilitated sedimentation of finely bedded volcaniclastic silt- and sandstones with abundant stromatolitic limestone interbeds in moderately shallow, below storm wave base waters distal to active volcanic centres (Allen et al. 1996). This more fine-grained upper part of the volcanic succession forms the host to the majority of iron oxide and polymetallic sulphide deposits in the BLU (Stephens et al. 2009; Stephens & Jansson 2020).