Explore the vast range of titles available.

The Durness Group of NW Scotland records deposition on the Laurentian margin from the basal Miaolingian (Cambrian, 509 Ma) to the Dapingian–Darriwilian boundary interval (Middle Ordovician, 470.3–468.9 Ma). The 930 m thick succession of peritidal and subtidal carbonates was deposited on the Scottish promontory, a nearly 120° deflection in the Palaeozoic continental margin between the Appalachian and Greenland sectors. These sediments were deposited as part of the Great American Carbonate Bank, a non-uniformitarian, continent-scale carbonate platform developed on the peneplaned craton. Measurement and description of a bed-by-bed composite section through the Durness Group provide a high-resolution reference framework that integrates conodont biostratigraphy, chemostratigraphy and sequence stratigraphy, including correlation with the Sauk megasequence and its subdivisions. The Sauk II–Sauk III sequence boundary marks the base of the group. The top of the group is faulted against rocks of the Moine thrust zone, generated by the Scandian orogeny, but sedimentation was probably terminated by the earlier Grampian arc–continent collision at 470–469 Ma. The highly mature quartz arenites of the underlying Ardvreck Group (Cambrian Series 2) indicate that there was no source-to-sink depositional continuity from the Hebridean foreland to the Dalradian Supergroup, which has coeval clastic sedimentary rocks of contrasting composition.

The sandstone layer connectivity in coal measure strata is one of the key factors in CBM escape in underlying coal seams, which lacks systematic research currently. This study aimed to explore sandstone layer connectivity and its control on CBM accumulation, taking the Lower Shihezi Formation in Qinan Coal Mine, Xuzhou–Suzhou Region, China, as a case study; to do so, we studied the No. 7 coal CBM unit, the pore-rich sandstone layers, and their connectivity modes by performing sequence stratigraphic analysis on the borehole cores, the logging data, and the theory of sequence stratigraphy and sedimentology, combined with the accumulation characteristics of the No. 7 coal seam CBM. This study shows the following: (1) The sequence stratigraphic framework of the Lower Shihezi Formation in the research region consists of two third-class sequences and six system tracts. (2) The No. 7 coal seam CBM unit includes the CBM formation layer, the connectivity layer, and the stable capping layer. (3) There are 10 types of parasequences in the No. 7 coal connectivity layer, and the pore-rich sandstone layers are all located in the connectivity layer and connected in three modes (vertical connectivity, lateral connectivity, and non-connectivity). (4) The connectivity modes and the thickness of pore-rich sandstone layers control the CBM accumulation in the region. Where the pore-rich sandstone layers are thickest and display vertical connectivity, the strong CBM desorption and escape lead to low CBM; where the pore-rich sandstone layers are thinnest and unconnected, the weak to no CBM desorption and escape result in high CBM. (5) Three models for sandstone layer connectivity and its control on CBM accumulation include the CBM weak accumulation model with a strong source supply, large basin subsidence, and undercompensation deposition; the CBM moderate accumulation model with a moderate source supply, moderate basin subsidence, and overcompensation to isostatic compensation deposition; and the CBM strong accumulation model with a weak source supply, small basin subsidence, and undercompensation deposition.

Globally Cenozoic interval witnessed recurrent climatic change of warming and cooling episodes of various magnitudes. The geological archives of the western part of the Kutch Basin are bestowed with spectacular igneous structures formed during the Deccan Trap volcanism. Overlying, Cenozoic successions of the Kutch Basin also get affected by the global climatic perturbations, which get registered in their impressive stratigraphic successions. Sedimentation in the basin was primarily controlled by the rate of relative sea-level fluctuations vs. background siliciclastic supply. Combined effect of climatic perturbations and relative sea-level fluctuation along passive-margin setting resulted in the occurence of variety of fossils, lithology and sedimentary structures, available all over the Cenozoic outcrops. To conserve and protect endangered geological features, geoscientists around the world have recognized several geosites, which can serve as standard reference section for further research and sustainable development for generations. In this study, we identify some spectacular outcrops from the western parts of the Kutch Basin (Cenozoic outcrops and Deccan Trap exposures) and document their properties to be recognized as potential geosites. These sites preserve exclusive geological features and provide template to understand the geological processes, however, needs conservation and protection. We propose the following assorted geosites viz. (1) Entablature geosite, (2) Pillow lava geosite, (3) Taphonomy geosite, (4) Fossil crab geosite, (5) Trace fossil geosite and (6) Soft sediment deformation (SSD) geosite. These sites may serve as exclusive locations for students field excursion, field-training for diverse professionals, social outreach activities and future reference section; indeed helps to achieve the implementation of some of the geoheritage goals. Diverse and unique geological features can be easily approached by thoroughly connected rail network and metalled roads.

Detailed sedimentological investigations of the Lower Cretaceous succession of southernmost Spitsbergen indicate deposition during a long-term fall and rise in relative sea level. The Rurikfjellet Formation shows an overall regressive development and consists of offshore deposits grading upwards into progradationally stacked shoreface parasequences. The overlying Helvetiafjellet Formation shows a two-fold division reflecting an overall transgressive development. The lower Festningen Member represents a lateral extensive sandstone sheet that was deposited in a braid plain setting with sediment dispersal to the south-east. The unit also includes a lower Barremian subaerial unconformity at its base, demonstrating that uplift and shelf erosion also took place in southern Spitsbergen. Clinoforms observed in seismic data from, amongst others, the Lower Cretaceous in the western Bjarmeland Platform suggest a potential link between the onshore unconformity and the offshore clinoforms. The Festningen Member is capped by a coaly shale unit that represents an expansion surface which marks a change into a high-accommodation distributary fluvial system of the overlying and heterolithic Glitrefjellet Member. The overall transgressive development recorded in the Helvetiafjellet Formation eventually resulted in a marine flooding that eroded and drowned the delta plain depositing an offshore mudstone unit, 5-10 m in thickness, that marks the re-establishment of open marine shelf conditions in the basal part of the Carolinefjellet Formation. The succeeding sand-rich part of the Carolinefjellet Formation contain abundant hummocky cross-stratified sandstones deposited in an inner shelf setting, and therefore represents renewed shoreline progradation onto the shallow subaqueous shelf.

An integration of lithostratigraphy and general sedimentary facies character for non-marine rocks can be a powerful tool in understanding the sequence stratigraphic architecture of the subsurface latest Silurian to Early Devonian Winduck Interval in the Blantyre and western Neckarboo sub-basins, central Darling Basin. This study integrates wireline logs (gamma ray and resistivity), cores and cuttings data to determine the sequence stratigraphic subdivision of the study area. The lithostratigraphy of the Winduck Interval could be subdivided into three units (A, B and C, in ascending order) in the four available wells (Mount Emu 1, Kewell East 1, Booligal Creek 1 and Booligal Creek 2). Closer study of the sequence stratigraphy in the approximately 850-m-thick Winduck Interval revealed ten parasequences (A–J) in progradational to retrogradational parasequence sets and three main Winduck sequences, WKS1, WKS2 and WKS3. Use of the suggested sequence stratigraphic model of the Winduck Interval has the potential to refine existing lithostratigraphic schemes and, given the higher resolution and more detailed correlation, may significantly improve subsurface stratigraphic reconstructions and aid in prediction of hydrocarbon-bearing reservoirs.

The Sylhet trough located on the north-eastern margin of present Bengal basin, contains ∼22 km of Tertiary sediments and well known as a hydrocarbon producing province. A detailed facies characterization of the subsurface Miocene Surma Group sediments (especial emphasis on reservoirs sandstones) from Jalalabad gas field within the Sylhet trough has been done using core log analysis and wireline log (gamma ray) interpretation. Texture and sedimentary structures of the cores suggests that the nine individual lithofacies types which can be grouped together into three facies associations, namely, fine-grained facies associations (FFA), medium-grained facies association (MFA) and coarse-grained facies associations (CFA). Major changes in gamma ray log motifs and various bounding discontinuities indicate six para-sequence sets (basin wide) and twenty eight para-sequences (local environmental changes) within the depth range from 2200-2800 m. Detailed facies analysis of the cores and wireline log reveals that the interbedding facies within the associations in the Surma Group commonly develop small-scale fining-upward (FU) cycles, coarsening-upward (CU) and random intercalations (RD). The sediments of the Surma Group of the Jalalabad field have been interpreted as deposits of the shallow marine to tide-dominated deltaic depositional setting. The cyclic nature of sedimentation pattern of the Surma Group probably records an almost continuous existence of this prograding deltaic regime and a tectonic setting characterized by a mixture of prolonged basin subsidence and regional transgression coupled with sporadic regressive phases.

Shale parasequence analysis is an important part of sequence stratigraphy sudies. This paper proposed a systematic research method for analyzing shale parasequences including their delineation, division, characteristics and origins. The division method is established on the basis of lithofacies. Multi-method analysis and mutual verification were implemented by using auxiliary indicators (such as mineral compositions, geochemical indicators and wavelet values). A typical shale parasequence comprises a lower interval of deepening water-depth and an upper interval of shallowing water-depth (e.g., a shale parasequence including a high-total organic carbon (TOC) shale-low-TOC limy shale). Abrupt increases in pyrite content, TOC value, relative hydrocarbon generation potential ((S1+S2)/TOC), and wavelet values are indicative of parasequence boundaries. The proposed research method was applied to study the upper fourth member of the Shahejie Formation in the Dongying depression, Bohai Bay Basin. Results show that there were seven types of parasequences developed. A singular and a dual structured parasequences were identified. Three factors controlling the development of the shale parasequences were identified including relative lake level change, terrestrial input and transgression. The development of high-TOC (>2%) shale parasequences was mainly controlled by biological and chemical sedimentation. The low-TOC (<2%) shale parasequences were mainly deposited by chemical sedimentation. The diversities of shale parasequences were caused by four major controlling factors including climate, relative lake level change, terrestrial input and emergency (e.g., transgression).

During the Late Carboniferous, a spacious warm-water carbonate platform developed across the eastern part of the present Arctic archipelago of Svalbard. The platform initiated in the Moscovian on an uplifted fault block (Ny Friesland High) and progradated during the Late Moscovian to Early Kasimovian into the adjacent Campbellryggen Basin (central Spitsbergen). The fossiliferous platform strata are characterized by a pronounced cyclicity formed by stacked parasequences, which consist of defined, subtidal to supratidal facies-set successions reflecting a general shallowing of the depositional area. Up to 17 of these shallowing-upward cycles, bounded by distinct discontinuity (marine flooding) surfaces due to the recurrent emersion and subsequent flooding of the platform surface, have been recognized within the platform strata. The stacked cycles are the result of global, glacio-eustatic, high-frequent and high-amplitudinal sea-level fluctuations with eccentricity periodicities caused by ice volume changes during the Gondwana Land glaciation. Based on systematic changes of the cycles (thickness and internal facies composition), the upper part of the platform strata is interpreted as a progradational parasequence set of a late highstand system tract.

An attempt is made to work out the sequence stratigraphic frame work of Infra and Intertrappean beds exposed in Soma quarry section, near Gowripatnam, Rajahmundry area to understand the mode of depositional process in the basin by integrating litho and biostratigraphic data. The study documents the field data to recognize some of sequence parameters in the field. The sequence stratigraphic study shows the Sequence Boundary, Transgressive Systems Tract (TST), three shallowing upward sequence, Maximum Flooding Surface (MFS) and Highstand Systems Tract (HST) deposits got exposed as a result of basinal rise and fall.

The sea-cliffs of Ogmore-by-Sea in Glamorgan, South Wales, expose a succession of Early Jurassic nearshore carbonates that drape rocky palaeoplatforms. A sequence-stratigraphic interpretation allows the recognition of four retrogradationally stacked parasequences, the internal facies architecture of each of which is controlled by the bathymetry and geometry of the underlying shore platforms. Preserved facies are interpreted as representative of foreshore, shoreface and offshore environments. Supratidal facies are absent, but representative storm-terrace clast assemblages are preserved in all lithofacies as a result of the cannibalization of the backshore during periods of shoreline retreat driven by sea-level rise. Biostratigraphical calibration allows the reconstruction of sea-level history and the correlation of regionally important flooding surfaces in the Rhaetian-Sinemurian of Southern Britain with the position of the contemporary shoreline. This suggests that platform incision in South Wales occurred several million years before the onset of major deposition; superseding deposits above ancient rock shore platforms may therefore not be representative of the environment in which coastal incision took place. As one of the best examples of its kind, the rockshore at Ogmore acts as a deposystem model for ancient rocky shores worldwide.