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Holocene evolutionary history of the Banni Plain in the Great Rann of the Kachchh Basin is reconstructed from a subsurface sediment core of ca 50 m. Detailed data on textural and lithofacies variations, grain‐size analysis, environmental magnetism and accelerator mass spectrometry 14C dates on seven samples were generated on the sediment core retrieved from the Banni Plain near Berada. A high‐resolution record extending back to 10 ka has been reconstructed from the top ca 40 m of the core section comprising shallow marine sediments. The core is divisible into five depositional units. The basal part is a fluvial depositional unit followed upward by estuarine, sub‐tidal, intertidal and supra‐tidal environments. The sediment accumulation rate is highest in the sub‐tidal to intertidal facies (1.9 cm year−1) and decreases towards the supra‐tidal facies to 0.09 cm year−1. Environmental magnetic analysis, χlf coupled with the S‐ratio, indicates high magnetic mineral concentrations during the Early Holocene, suggesting a wet period accompanied by high monsoon precipitation. This is followed by the onset of semi‐arid conditions in the Great Rann of the Kachchh Basin as indicated by the low values of the χlf and S‐ratios. A westward and northward shift in the shoreline towards the deeper part of the basin is suggested during the Late Holocene, which is coupled with aridity and reduced monsoonal conditions. The change in depositional pattern from the retrogradational deposit of fluvial (Unit 1) to estuarine sediment (Unit 2), progressing to sub‐tidal (Unit 3), is attributed to sea‐level transgression followed by regressive intertidal (Unit 4) to supra‐tidal deposition (Unit 5), culminating in complete withdrawal of the sea, aided by tectonic uplift, during the Late Holocene. The results reveal that the sediment accumulation rates and depositional environments changed over time in response to changes in sea level from minima to maxima and then eventually to the present level. [ABSTRACT FROM AUTHOR]

Lithofacies and palynofacies studies was conducted on the Late Cenomanian to Early Turonian sediments of Dukul Formation from the Yola Sub-basin, Northern Benue Trough, northeastern Nigeria. This is with the aim to determine the paleodepositional environment of the studied sediments. Based on lithofacies analysis, three (3) facies were identified; shale, mudstone and limestone lithofacies. The sediments were inferred to have been deposited in shallow marine (shelf) environment below the mean fair-weather wave base (FWWB). Palynofacies analysis also suggest a distal oxic-dysoxic to relatively anoxic shelf environmentthat was responsible for the deposition of the sediments. This is in agreement with the shallow marine depositional environment as shown from lithofacies. The distal dysoxic condition could have been due to the sea-level drop of the continental shelf. [ABSTRACT FROM AUTHOR]

Carboniferous units in southern Mexico consist of mixed carbonate-volcaniclastic facies representing shallow marine environments, from the middle ramp to shallow subtidal environments in the inner ramp. The Tournaisian-Visean Santiago Formation is characterized by the dominance of mixed clastic and bioclastic sediments in a mid-ramp setting without a supply of volcanic material within the basin. Instead, the newly reported locality of the Mississippian-Pennsylvanian Ixtaltepec Formation is a mixed succession of volcaniclastic and carbonated sediments deposited under a tidal influence in the middle to the inner ramp. The age is determined to be late Visean and early Serpukhovian (∼333-325 Ma) based on the presence of Actinoconchus lamellosus , Syringothyris sp., and Punctospirifer sp. and corroborated by geochronological data. This study provides new evidence of Carboniferous volcanism in the sediment-sources area in southern Mexico. Volcanic activity in the area is linked to the subduction of the oceanic crust of the Rheic Ocean, which resulted in the formation of magmatic arcs on the Gondwanan realm and the assembly of Pangea. During the Early Mississippian to early Permian, extensive areas of the northwest of South America and southwest of North America were covered by epicontinental seas. Sedimentation in the area was mainly characterized by shallow clastic-carbonate-dominated environments and deep marine settings, where basins within the peri-Gondwana Terranes received volcanic detritus from the North Gondwana and western Pangea arcs. • Carboniferous successions in southern Mexico comprise mixed carbonate–siliciclastic sediments that represent environments from the middle ramp to inner ramp. • The Mississippian-Pennsylvanian Ixtaltepec Formation is characterized by a mixing of volcaniclastic sediment with carbonate-siliciclastic sediment. • The Ixtaltepec Formation was deposited under a tidal influence. • Volcanogenic sediments are interpreted as pyroclastic surges and airfall deposits. • Volcanic activity is linked to the subduction of the oceanic crust of the Rheic Ocean and subsequent closure, which resulted in the formation of magmatic arcs on the Gondwanan realm. [ABSTRACT FROM AUTHOR]

Synaeresis cracks are observed at different stratigraphic levels in shallow marine mixed siliciclastic-carbonate sediments of the Middle Jurassic rocks of the Patcham Island, Kachchh, Western India. Cracks are preserved as cast or grooves in micritic sandstone of the Kuar bet member of Kaladongar Formation and sandy allochem limestone of the Raimalro Limestone member of Goradongar Formation. It bear distinct morphology of simple, straight to gently curved, spindle-shaped, irregular, unbranched to branched at acute angle; interconnected curlicue forms of non-orthogonal pattern. The X-radiography shows sharp margin and tapering twigs which support to nullify the possible biogenic origin. These cracks are developed at sediment-water interface and sediment-sediment interface in aqueous conditions, where partial dewatering of sediments causes reduction of sediment volume and loss of plasticity. Formation of cracks are also post-depositional phenomenon operated during initial phase of diagenesis where induced stress is generated due to compaction of sediments and neomorphism/recrystallisation of the susceptible carbonate grains. [ABSTRACT FROM AUTHOR]

The Middle Jurassic rocks of the Kaladongar Formation well exposed in the Kaladongar Hill range of the Patcham Island and Kuar Bet of the Northern Kachchh comprises of ∼450 m thick sequence of mixed siliciclasticcarbonate sediments intercalated with shales. These Mixed siliciclastic-carbonate sediments show wide variation in textural and mineralogical composition and represent genetically related six rock types: micritic sandstone, allochemic sandstone, sandy allochemic limestone, micrtic mudrock, sandy micrite and muddy micrite; which are highly bioturbated and show behaviourally diverse groups of trace fossils. Total 34 ichnogenera are identified, which includes, Arenicolites, Asterosoma, Beaconites, Bergaueria, Chondrites, Cochlichnus, Dactylophycus, Daedalus, Didymaulichnus, Diplocraterion, Gordia, Gyrochorte, Gyrolithes, Ichnocumulus, Laevicyclus, Lockeia, Margaritichnus, Monocraterion, Nereites, Ophiomorpha, Palaeophycus, Phoebichnus, Phycodes, Pilichnus, Planolites, Plug Shaped Form, Protovirgularia, Rhizocorallium, Scolicia, Skolithos, Taenidium, Teichichnus, Thalassinoides and Walcottia. These trace fossils are classified into six morphological groups namely, circular and elliptical structures; simple structures; branched structures; rosette structures; spreiten structures; and winding and meandering structures. These trace fossils are further group into eight assemblages which occurred together into mixed siliciclastic-carbonate sediments, include, Asterosoma assemblage, Gyrochorte assemblage, Rhizocorallium assemblage, Thalassinoides assemblage, Planolites-Palaeophycus assemblage, Phycodes assemblage, Ophiomorpha assemblage and Skolithos assemblage. The recurring pattern of these assemblages through the sequence displays the development of Skolithos and Cruziana ichnofacie s and at places the mixed Skolithos-Cruziana ichnofacies which suggest a low wave and current energy conditions with intervening period of high wave and current energy conditions and an intermediate period of stressful environments, respectively. Sedimentological and ichnological data suggest that the deposition of the mixed siliciclastic-carbonate sediments of the Kaladongar Formation took place in the foreshore to offshore environment under fluctuating wave and current energy condition. [ABSTRACT FROM AUTHOR]

Abstract: The northern Wanganui Basin, New Zealand, is one of the key global sites for understanding marine cyclic sedimentation during the Quaternary. This paper presents the first evidence of marine cyclic sedimentation from its central-southern parts. Sedimentological, micropalaeontological and palynological analyses on a 280-m-deep borehole encountered units dating back to MIS 10. The sequence includes four marine cycles spanning MIS 9–5, which are overlain by terrestrial fluvial aggradation surfaces dating from MIS 4–2. Each marine unit represents a progressively shallowing depositional environment from the mid-shelf to coastal plain. This is overlain by a terrestrial sequence of lowstand fluvial terraces. Localized fault movements appear to have influenced the sedimentary character of the sequence during MIS 7a and 5e producing basement highs which provided protection to the shoreline. The cyclothems described in this paper now extend the already extensive, previously described record from MIS 17–10 to produce a combined eustatic record of Quaternary sea level change within the basin to MIS 5. They also provide an excellent example of the sedimentary response of a coastal basin to a progressive loss of sedimentation accommodation space. [Copyright &y& Elsevier]

A series of wave-tunnel experiments was conducted to investigate the conditions under which hummocky and swaley cross-stratification form. Isotropic 3-dimensional (3-D) hummocky bed forms were generated under long wave periods (~8-10 s) and moderate oscillatory velocities (Uo ~50-90 cm/s) with very weak (< 5 cm/s) to no unidirectional flow. Hummocks became anisotropic with the addition of only a small unidirectional current (5-10 cm/s), and began to resemble unidirectional dunes when the unidirectional current was increased above 10 cm/s. Synthetic aggradation of the hummocky bed forms at high (4.2 mm/mm) and low (1 mm/mm) rates generated stratification resembling hummocky and swaley cross-stratification, respectively. Based on these findings, we suggest that hummocky cross-stratification optimally forms above (but near) storm wave base where aggradation rates during storms are high enough to preserve hummocks but unidirectional current speeds are sufficiently low to generate low-angle, isotropic cross-stratification. Swaley cross-stratification is also hypothesized to be deposited by an aggrading hummocky bed between fair-weather and storm wave base, but in shallower water where aggradation rates are low enough to cause preferential preservation of swales. [ABSTRACT FROM AUTHOR]

The article presents several studies that examine the Jurassic sedimentary succession in North-East Greenland. These studies deal with stratigraphic and depositional aspects of the Middle-Upper Jurassic sediments from isolated and popular localities outside the main outcrop areas. In one study, the stratigraphic development of the Jurassic succession in south-east Traill Ø comprising the E-tilted Bjørnedal Block bounded to the west by the Vælddal Fault is explored. Another study examined the formation of the Bristol Elv Formation.