Angular Unconformity Research Articles

The technical challenges and outcomes of ground-penetrating radar: A site-specific example from Joggins, Nova Scotia

The Carboniferous Joggins Formation is known for its complete succession of fossil-rich, coal-bearing strata, deposited in a fluvial meanderbelt depositional setting. Hence, the Joggins Formation outcrop is an excellent analogue for studying the 2D geological complexities associated with meanderbelt systems. In this research, a conventional ground-penetrating radar system was tested with the intent of imaging near-surface, dipping, strata of the Joggins Formation (potentially with subsequent repeats as annual erosion provides new visual calibrations). The survey was unsuccessful in its primary goal, and for future reference we document the reasons here. However, the overlying near-surface angular unconformity was successfully imaged enabling mapping of the approximately 8 m of overlying glacial till. A successful outcome would have allowed observations from the 2D outcrop to be extended into 3D space and perhaps lead to an increased understanding of the small (e.g., bedform baffles and barriers) and large (e.g., channel bodies) scale architectural elements, meanderbelt geometry, and aspect ratios. The study comprises a 42-line, 3.46 km ground-penetrating radar survey using a Sensors and Software pulseEKKO Pro SmartCart system. It was combined with a real-time kinematic differential global positioning system for the georeferencing of survey lines. The 50 MHz antenna frequency, with a 1 m separation, was chosen to maximize the depth of penetration, while still maintaining a reasonable resolution. The results show that many of the lines are contaminated with diffraction hyperbolae, possibly caused from buried objects near or under the survey lines or surface objects near the survey lines. A total of thirteen unique radar reflectors are described and interpreted from this work. The thick clay-rich soil overlying the Joggins Formation probably contributed to significant signal attenuation and the nature of the Carboniferous strata (dip of the beds, pinching and swelling of the beds, bed thickness, etc.) also contributed to imaging difficulties.

Late Cretaceous transtensional faulting of the Apulian Platform, Italy

This work focuses on the structural setting of a small area of the Murge Plateau, southern Italy, exposing Turonian bauxites and encompassing Upper Cretaceous carbonates of the Apulian Platform. By combining field geological and structural mapping with mineralogical and petrographic investigations of representative rock samples, we document the control exerted by Late Cretaceous, syn-sedimentary, high-angle faults and dilational fissures striking ca. N105E, N135E, N170E, and N45E. Altogether, these structural elements formed a few km-long, transtensional fault system along which karst-related shafts, dissolution caves, and sinkholes developed. Karst processes first affected the topmost limestone beds of the Valanginian-Cenomanian Bari Fm. Then, during Turonian, in a continental setting, cycles of terrigenous sediment deposition and weathering localized in the karst-related cavities, dilational fissures, and at the top of down-dropped fault blocks. Weathering of the Al–Si rich sediments formed bauxites made up of kaolinite, boehmite, goethite, hematite, and anatase mineral phases. The relative enrichment in kaolinite with respect to boehmite documented for the breccia and conglomerate matrix topping the bauxites is interpreted as due to lower degrees of weathering. Differently, the individual bauxite beds do not show any internal significant variation in terms of their mineral assemblages, but form angular unconformities due to syn-sedimentary faulting. The subsequent marine transgression also occurred under the influence of active tectonics, as displayed by growth folds at the bottom of the Conacian-Early Campanian Altamura Fm. The overall results of this study are in agreement with those previously reported for nearby areas of the Murge Plateau exposing Santonian limestone rocks of the Altamura Fm. Accordingly, we infer that Late Cretaceous transtensional faulting of the Apulian Platform was due to a far field stress state, likely associated to the orogenic processes that involved the northern edge of the Adriatic micro-plate.

Early Devonian tectonic conversion from contraction to extension in the Chinese Western Tianshan: A response to slab rollback

Abstract Extensive angular unconformities that occur across the Tianshan Orogen provide insight into the Paleozoic tectonic evolution of the southwestern Central Asian Orogenic Belt. This study presents new geochronological and geochemical data to unravel the age and origin of a pronounced angular unconformity in the Baluntai domain of the Chinese Western Tianshan. The angular unconformity separates a ductilely deformed metamorphic complex from overlying unmetamorphosed sequences. Detrital zircon age spectra suggest that the sedimentary samples received detritus from both the Precambrian basement and contemporaneous igneous rocks in the Central Tianshan and Yili blocks. The youngest detrital and metamorphic zircons in metasediments from the metamorphic complex reveal that their protoliths were deposited at ca. 419 Ma, and subsequently overprinted by metamorphism and ductile deformation at ca. 409 Ma. Along with ca. 532–407 Ma metavolcanics and foliated intrusions, the metamorphic complex constitutes a diachronous stratigraphic unit deposited during early Cambrian to late Silurian times, rather than a Precambrian basement as previously thought. The youngest detrital zircon age data from siliciclastic samples immediately above the angular unconformity constrain their deposition to ca. 407–397 Ma. In conjunction with a ca. 406 Ma rhyolitic tuff in the lower terrestrial siliciclastic unit and an early Carboniferous paleontological age of carbonates in the upper shallow-marine unit, it is suggested that the overlying unmetamorphosed sequences were accumulated during the early Devonian to the early Carboniferous. Thus, the angular unconformity in the Baluntai domain was formed between ca. 409 and 407 Ma. New and already published geochemical data reveal that the early Paleozoic (ca. 530–410 Ma) and late Paleozoic (ca. 410–320 Ma) igneous rocks are mainly medium- to high-K calc-alkaline I-type granitoids, which exhibit typical subduction-related geochemical signatures despite contrasting structural features. These geochronological and geochemical results are in accordance with those of similar early Devonian angular unconformities and Paleozoic igneous rocks in the southern Yili Block. The early Paleozoic igneous rocks display highly scattered zircon εHf(t) values, while the late Paleozoic rocks show a progressively increasing trend toward more positive values, attributed to slab rollback of the northward subducting South Tianshan Ocean under the Yili and Central Tianshan blocks. Thus, we propose that the formation of the angular unconformity was caused by tectonic conversion from contraction to extension due to slab rollback during the early Devonian. This study highlights the significance of geological and geochronological investigations of angular unconformities in the context of associated episodic magmatism and slab behavior in order to unravel distinct tectonic processes in the long-lived accretionary evolution of the Chinese Western Tianshan.

Back-arc tectonic tempos: Records from Jurassic–Cretaceous basins in the eastern North China Craton

Magmatic and structural tempos have been recognized in continental magmatic arcs, such as Cordilleran and Andean arcs. However, it remains unclear whether similar tempos or episodicity occur in back-arc settings, knowledge of which would be crucial for understanding back-arc geodynamics. The western Liaoning (WL) region in eastern China contains well-preserved basins of Jurassic–Cretaceous age and provides an opportunity to investigate back-arc tectonic processes. We present stratigraphic, structural, and geochronological data from the WL region to constrain tectonic evolution during the Jurassic–Cretaceous. The results show four stages of rifting or extension during 190–168, 167–137, 136–97, and 96–70 Ma, indicating a duration of 20–40 Myr for each extensional stage. Aside from a magmatic lull at 96–70 Ma, volcanism was associated with each of the three earlier extensional stages. Each main period of volcanism had a duration of 10–20 Myr, with the main eruption events occurring on an average cycle of ~25 Myr. The Jurassic–Cretaceous extension and rifting were interrupted by three compressional events at 168–167, 137–136, and 97–96 Ma, as evidenced by angular unconformities, basin inversion, and structural shortening. Each episode of compression lasted for ~1 Myr, on a 30–40 Myr cycle. The results indicate tempos in both back-arc stress state and magmatism. The back-arc tectonic evolution was characterized by frequent alternation of long-lived extensional and short-lived compressional events, and the back-arc magmatism in all cases occurred in an extensional setting. The back-arc tectonic tempos can be explained by a slab-driven model involving control by alternating phases of slab rollback and retreat on back-arc stress states and magmatism.

Tectonic Structures in the Southeastern Flank of the Junction Zone Between the In’yali-Debin Synclinorium and the Omulevka Terrane (Kolyma-Omolon Microcontinent, NE Asia)

The study area is located in the zone of junction of the In’yali-Debin synclinorium and the Omulevka terrane (Kolyma-Omolon microcontinent of the Verkhoyansk-Kolyma fold belt). The main tectonic structure is the Momontai syncline made of Middle Jurassic clastic rocks overlain by Upper Jurassic volcanic and volcaniclastic rocks of the Uyandina-Yasachnaya volcanic arc. The Au and Au-Ag occurrences known here are confined to NE-trending faults and hosted in subvolcanic and volcanogenic rocks, mainly rhyolites and dacites. The studied Middle Jurassic rocks are found to be characteristic of near-shore shelfal environments changing, in certain time intervals, to deltaic conditions of sedimentation. The presence in the conglomerates and sandstones of large poorly rounded quartzite and carbonate fragments and of mudstone and volcanite pebbles indicates a proximal provenance of the clastics. For the first time we established a sharp angular unconformity between the intensely deformed Middle Jurassic and Upper Jurassic rocks in the region. Relations between the Late Jurassic subvolcanic deposits and the host rocks were studied. The carried out structural and tectonophysical investigations showed that folding occurred in two deformation stages. During the first stage, the Middle Jurassic clastic rocks were draped into small recumbent to isoclinal folds, cylindrical and parallel-type, with a NW strike. Cleavage is rare. The structural paragenesis of bedding-plane detachment faults, thrusts, normal faults, and strike slip faults is found to have formed in a single stress field together with the development of folds of the first deformation stage. The intensity of the first-stage folding increases from west to east. Restored are axes of paleostresses responsible for the formation of fold-and-thrust structures of the first deformation stage. The Upper Jurassic volcanogenic-sedimentary strata were deformed into superposed large, simple, open folds of the second stage, which exhibit sublatitudinal orientation. They associate with small-scale thrusts and, rarely, strike-slip faults. It is recognized that in the late Middle Jurassic or the early Late Jurassic the region was affected by intense folding which produced tectonic structures of NW strike. Accumulation of the Late Jurassic volcanogenic rocks and intrusion of subvolcanic deposits occurred on/into the earlier deformed Middle Jurassic rocks.

Aptian Flysch in Central Tibet: Constraints on the Timing of Closure of the Bangong‐Nujiang Tethyan Ocean

AbstractThe timing of the closure of the Bangong‐Nujiang Tethyan Ocean is highly controversial. An important reason for this is that the sedimentological work within the Bangong‐Nujiang suture zone is not sufficient. In this study, based on the U‐Pb zircon dating of turbiditic sandstone and tuff interlayers, we determine the existence of Aptian flysch (ca. 126–113 Ma) in the middle and western segments of the Bangong‐Nujiang suture zone. Further analysis shows that the Aptian flysch was deposited in a trench environment. In space, from the Mabujia Co area in the western segment to the Kama area in the middle segment, the outcrop extent of the Aptian flysch spans nearly 300 km from east to west. These results indicate that the Bangong‐Nujiang Tethyan Ocean had not fully closed by the end of Aptian time, and its oceanic slab was still subducting. Based on this new discovery, and the results of previous studies, we believe that the middle and western segments of the Bangong‐Nujiang Tethyan Ocean closed between 113 and ca. 92 Ma nonmarine deposition of the Jingzhushan Formation, which lies in angular unconformity above the flysch.

Exhumation and structural evolution of the high-elevation Malcante Range, Eastern Cordillera, NW Argentina

As an integral part of the Eastern Cordillera, the fault-bounded Malcante mountain range (up to 5100 m) in the NW Argentine Andes (ca. 25°S) is located in the transition between the arid Puna Plateau to the west and the humid broken foreland to the east. At this latitude, the topographic gradient of the eastern Andean margin forms an efficient orographic barrier that causes pronounced east–west rainfall and surface-process gradients. In this setting, the Malcante Range is an important, yet poorly studied structural high formed during the Cenozoic topographic growth of the Central Andes. In this study, we combine (a) detailed field observations, (b) a two-dimensional structural reconstruction, (c) apatite fission track and (U–Th-Sm)/He thermochronology of bedrock samples from a vertical transect across the western flank of the Malcante Range, and (d) inverse thermal modelling using QTQt software with the aim of deciphering the exhumation history of this mountain range. Field data indicate the presence of an angular unconformity between Cenozoic foreland deposits and older sedimentary strata, suggesting an initial episode of deformation during the middle-late Eocene, while our thermal model constrains the onset of exhumation at ~10 Ma. We suggest that exhumation was related to the unroofing of the easily erodible sedimentary cover, which prevented significant initial surface uplift. This may have changed as more resilient bedrock was exposed at ~5 Ma according to the thermal model, promoting rapid rock uplift. In combination with published data, our thermochronology allows us to speculate on the existence of a zone of deformation concentrated in the area of the present-day Pasha (24.5°S), Malcante (25°S), and Agua de Castilla (25.4°S) mountain ranges by ca. 10 Ma.

Structural style of buried Ediacaran basins in Saudi Arabia on seismic reflection data

Several isolated Ediacaran basins subcrop Phanerozoic strata in Saudi Arabia. The structural styles of these subcropping basins are reviewed here based on interpretation of 2D and 3D seismic reflection data and comparison with Arabian Shield outcrops. The basins are distinguished by layered seismic reflectors that are interpreted as sedimentary and volcanic strata. Due to limited well penetrations these packages cannot be directly dated but a relative chronology is established, anchored by constraints from the Arabian Shield and regional studies. Most of the basins are bound by extensional faults and the basin fills show growth architectures and angular unconformities. The bounding faults trend broadly north–south and are interpreted to be late to post-orogenic reactivations of oceanic terrane margins. Based on their structural characteristics in comparison with sub-basins exposed on the shield, the basin fills are correlated with the Ediacaran Jibalah Group, an equivalent of the Omani Nafun Group. These sub-basins experienced inversion and exhumation prior to ongoing volcanism and unconformable deposition of late Ediacaran to earliest Cambrian Kurayshah Group sediments. The Kurayshah Group is disconformably overlain by the widespread Tayma Group siliciclastics. This disconformity correlates to the Angudan Unconformity in Oman. The Kurayshah Group includes a late Ediacaran stratovolcano over 40 km in diameter. In the eastern basins, evaporitic structural styles indicate the presence of Hormuz / Ara evaporites, with local igneous intrusions, that correlate at least in part to the Kurayshah Group. The Tayma Group infills significant accommodation space variations and was affected by ongoing but declining differential subsidence and reactivation of the underlying basin-bounding faults.

Sedimentology and stratigraphic development of sandy members of Pindiga formation, GONGOLA SUB-BASIN, northern Benue trough, Nigeria: A mixed wave, tide and fluvially influenced coastal system

This paper documents the detailed sedimentology and stratigraphic evolution of the Sandy members of the Pindiga Formation. Good understanding of this succession is relevant to resource exploration and exploitation in the frontier Gongola Sub-basin of the Northern Benue Trough and similar Cretaceous strata in general. Detailed facies analysis based on examination of twelve well exposed outcrops revealed four facies successions. Field relations show that the deposits are stratigraphically partitioned by a disconformity surface into two parts. The lower part consists of regressive wave-storm dominated deltaic and wave-storm dominated offshore to nearshore facies successions, while the upper part comprises of transgressive wave dominated estuary and tide dominated estuary successions. Fourteen facies were identified and organized into nine facies associations. Field observations show that the upper boundary of the Sandy members is an angular unconformity represented by the development of a thick paleosol unit below the Fika Shale. Conversely, the lower boundary is transitional. Contrary to earlier fluvial and coastal to littoral interpretation of the Sandy members, this work demonstrates that marine processes were important for facies development. It is shown that an integration of detailed facies and ichnological analyses is valuable in determining robust paleoenvironmental interpretations of sedimentary successions.

Tectonic setting of Cretaceous porphyry copper deposits of northern Chile (28°-30° S) and its relations with magmatic evolution and metallogeny

Cretaceous porphyry copper deposits of northern Chile (28º-29º30’ S) are genetically related with dacitic to dioritic porphyries and they represent a still poorly-explored target for Cu resources. The porphyries correspond to stocks distributed into two separated discontinuous NS trending belts of different age. The location of these porphyries is generally adjacent to orogen-parallel major fault systems that extend along the studied segment and also have a marked temporal relationship with deformation events registered along these structures. A first episode of Cu-bearing porphyry emplacement took place between 116 and 104 Ma (Mina Unión or Frontera, Cachiyuyo, Punta Colorada, Dos Amigos, Tricolor porphyries). These Early Cretaceous dacite to diorite porphyries are spatially associated with the eastern segments of the Atacama Fault System, which records sinistral transpression that started at 121 Ma producing ground uplift, consequent denudation and exhumation of the Early Cretaceous magmatic arc. This resulted in a change from marine to continental deposition with an angular unconformity in the site of the back-arc basin after of eastward migration of the deformation around 112-110 Ma. At the scale of the continental margin, this deformation is correlated with early stage of the Mochica Orogenic event described in Perú. A second episode of Cu-bearing porphyry emplacement occurred between 92 and 87 Ma (Elisa, Johana, Las Campanas and La Verde deposits), which are spatially and temporally associated with the regional-scale Las Cañas-El Torito reverse fault, active between 89 and 84 Ma, during the Peruvian Orogenic Phase. This fault up thrust to the west part of the Chañarcillo Group rocks (Lower Cretaceous) over the younger upper levels of the Cerrillos Formation (Upper Cretaceous). The integrated geological mapping and geochemical data of the Early to Late Cretaceous volcanic rocks indicates that both Early Cretaceous sinistral transpression and Late Cretaceous east-west compression were not significant in promote changes in magma genesis, except for slight changes in trace element ratios (increase in Th/Ta, Nb/Ta and La/Yb) suggesting that the Late Cretaceous deformation event produced only slightly increase in crustal thickness (>40 km), but far from being comparable to major Cenozoic orogenic phases, at least along the magmatic arc to back-arc domains in the study area. Finally, our study give insights about regional geological parameters that can be used as a first order guide for exploration of Cu resources along Cretaceous magmatic belts of northern Chile, where both Early and Late Cretaceous Cu-bearing porphyry intrusions are restricted to a large structural block bounded to the west and east by Cretaceous fault systems.

Apatite and zircon (U–Th)/He thermochronological evidence for Mesozoic exhumation of the Central Tibetan Mountain Range

The Central Tibetan Mountain Range (CTMR) exposes the oldest strata in the Qiangtang Terrane and may record the most complete exhumation history prior to and post‐collision of India and Asia. This article presents apatite and zircon (U–Th)/He thermochronology data of granites from the CTMR. Zircon (U–Th)/He single grain ages range from 116 to 191 Ma, while apatite (U–Th)/He single grain ages vary from 54 to 94 Ma. Thermal modelling results based on (U–Th)/He ages of apatite and zircon indicate that episodic rapid exhumations occurred at the Middle‐Late Jurassic and the Late Cretaceous, respectively. The Middle‐Late Jurassic exhumation is consistent with the provenance analysis of Jurassic strata in the South (SQT) and North Qiangtang Terrane (NQT) which suggested they were derived from the CTMR. This stage of rapid exhumation might be attributed to the northward ridge subduction of the Bangong‐Nujiang Ocean. The Late Cretaceous relatively rapid exhumation is compatible with the angular unconformity between the Abushan Formation and the underlying marine strata. This stage of exhumation may be caused by the collision between Lhasa and QT. Our results, combined with the crust shortening and adakitic rocks in the SQT during the Late Cretaceous, provide robust evidence for crustal thickening and early uplift of central Tibetan Plateau prior to the India‐Asia collision. The CTMR experienced very low exhumation since the early Eocene, implying that low‐relief topography had been established at high elevation with internal drainage prior to India‐Asia collision.

The Jáchal river cross-section revisited (Andes of Argentina, 30°S): Constraints from the chronology and geometry of neogene synorogenic deposits

In the southern Central Andes, between 27 and 33°S, a flab-slab subduction has been established since the last 10 Ma. This particular subduction geometry has been proposed to control the eastward migration of the deformation, with the Precordillera fold-and-thrust belt development and the uplift of the foreland Sierras Pampeanas basement blocks. In this study, we present a 190 km-long structural section, across the easternmost Cordillera Frontal, the Precordillera and the westernmost sector of the Sierras Pampeanas, and revise both previous kinematic models, and the relationship between the establishment of the flat-slab and deformation in the foreland. For this purpose, we integrate published sedimentological data with a new structural analysis. Our forward kinematic model is fed back by: (i) the geometries of Neogene deformed beds throughout the Precordillera, such as sedimentary wedges and angular unconformities; (ii) flexural subsidence due to the topographic and sedimentary loads for each deformation step, constrained by measured stratigraphic sections; (iii) a revised chronostratigraphy and correlation chart of the Cenozoic sedimentary units; and, (iv) recent constraints on the ages of activity of the faults. This allows us to build a model that considers the timing of deformation for each main structure and its relationship with sedimentation, producing a model with better geometrical, sedimentological and paleogeographical constraints than previous proposals.The results of this modelling are presented in six different evolutionary stages. During the first stage, between 19 and 15 Ma, the eastern Cordillera Frontal is uplifted, associated with subsidence in the Rodeo-Iglesia proximal foreland basin, and low subsidence in the Bermejo distal foreland basin. In the second stage, between 15 and 12 Ma, uplift of the Western Precordillera took place, associated with the creation of a shallow detachment beneath the Rodeo-Iglesia basin. The third stage, between 12 and 8 Ma, was the beginning of the Central Precordillera uplift and the first pulse of uplift in the Valle Fértil range. During the next stage, between 8 and 5 Ma, the Central Precordillera rapidly deformed. Between 5 and 2 Ma, deformation in the Western and Central Precordillera almost ceased, and the focus of contractional deformation shifted to the Eastern Precordillera. The last 2 Ma phase is characterized by strike-slip deformation in the Rodeo-Iglesia basin and contractional deformation in the Eastern Precordillera and the Valle Fértil range.The key results are that the amount of total shortening, 66 km (35%), calculated for the cross-section, is significantly less than previously proposed, and the detachment of the Precordillera fold-and-thrust belt is shallower (~6.5 km vs 16 km) than previous models. This last point allows us to connect the Cordillera Frontal with the Precordillera, with a ramp-plane geometry of the detachment, as previously suggested, but allowing at the same time the subsidence and the generation of the observed geometries in the Rodeo-Iglesia basin.

The first upper Silurian land-derived palynological assemblage from South America: Depositional environment and stratigraphic significance

A thick succession of quartz-rich sandstones cropping out in the middle part of the Villacorta Creek, on the western slope of the Sierra del Famatina (Valle Hermoso, La Rioja Province, northwestern Argentina) was recently recognized as the Villacorta Formation. The sandstone package rests disconformably on greenish sandstones of the Ordovician Suri Formation and is overlain along a marked angular unconformity by rocks of the upper Carboniferous Agua Colorada Formation (Paganzo Group). The Villacorta Formation is divided into four intervals, the lower one is formed by quartz-rich sandstones showing large-scale cross-stratification; the second part is similar but includes some levels of intraformational conglomerates and shows a decrease in both grain-size and the scale of the cross-bedding sets. The third section comprises medium- and coarse-grained sandstone with intercalation of fine-grained sandstones. The upper interval corresponds to two thickening and coarsening upwards successions. This last section was deposited in a deltaic environment where the top of mouth bars and lagoon deposits preserved palynological assemblages and phytodebris. A low-diversity palynological assemblage recovered from these mudstone levels includes abundant nematophyte cuticular-like fragments, cryptospores (monads, dyads, tetrads) and trilete spores (e.g., Scylaspora scripta, Emphanisporites protophanus). The stratigraphic relationships of the succession and the palynological assemblage suggest a late Silurian age for the Villacorta Formation. The exclusive presence of land-derived components in the organic residue allows to capture a snapshot of the terrestrial vegetation and constitutes the first record of this type of palynological association and nematophyte remains in this southern region. This assemblage improves previous paleogeographic reconstruction enlarging the extent of Silurian basins in Argentina. The shallowing successions of the Famatina region pass to marine deposits in the Precordillera area, indicating a westward transition to offshore environments.

Stratigraphy and sedimentology of the Pennsylvanian Grande Anse Formation, Cumberland Basin, eastern Canada: its relationship to salt tectonics and coeval strata of the Joggins World Heritage Site

The Cumberland Basin is one of several sedimentary basins composing the late Paleozoic Maritimes Basin complex of eastern Canada. Pennsylvanian salt tectonics in the Cumberland Basin caused two salt mini-basins to evolve on either side of the Minudie Anticline, a salt wall. South of the wall (Athol Syncline), along the Joggins World Heritage shoreline, an ∼3000 m succession of strata (Little River, Joggins, Springhill Mines, and Ragged Reef formations) accumulated conformably on the Boss Point Formation. North of the wall (Black Point sub-basin), the biostratigraphically equivalent, but mostly unstudied, ∼600 m thick succession of Grande Anse Formation lies in angular unconformity on folded and faulted Boss Point and basal Little River formations. Grande Anse Formation sedimentology indicates four lithofacies associations: floodplain (LA1), braided channel (LA2), sheet flood (LA3), and debris flow deposits (LA4). One possible model has the Black Point sub-basin with its own hydrological system, completely separated from the Athol Syncline. A low subsidence rate combined with the low sedimentation rate produced the ∼600 m thick sand- and mud-prone succession that was contemporaneous with the ∼3 km succession to the south. The second model proposes that north of the salt wall was exposed to erosion during accumulation of Joggins and Springhill Mines formation strata to the south. Subsequently, the sediment of the lithologically similar Ragged Reef and Grande Anse formations either (i) onlapped to the north, unconformably on the folded Boss Point; or (ii) unconformably–disconformably on the underlying strata after a period of time indistinguishable in the biostratigraphic record.

Grenville Foreland Deformation and Sedimentation in Southwest Ohio Indicated by Reprocessed Seismic Reflection Profiles near Middletown, Ohio, USA

The late Mesoproterozoic to early Neoproterozoic Middle Run Formation contains vital information about the crustal evolution of the North American Craton. Four reprocessed seismic reflection lines in the vicinity of the AK Steel facility in Middletown, Ohio, provide new insights into the structural and depositional setting of the Middle Run Formation in this region. A residual statics solution improved the resolution and coherency of reflections in these profiles that underlie the Cambrian Mount Simon Sandstone. Reprocessing revealed gently inclined, west-southwest-dipping reflectors and the occurrence of an angular unconformity between the Middle Run Formation and the overlying Paleozoic strata. The weak and discontinuous seismic reflection character of the Middle Run Formation in these seismic lines overlies a sequence of stronger parallel reflections that are like those observed on the eastward ODNR-1-88 seismic line located near core hole DGS 2627, the stratotype of the Middle Run Formation. This inferred thickness indicates that the basin in which the Middle Run Formation was deposited ranges from at least 670 to 1,128 m (2,200 to 3,700 ft) deep at the AK Steel area and dips gently west-southwest, which is in contrast with the moderate easterly dip observed on the ODNR-1-88 seismic line to the northeast. Correlation of these features across the 10 km (approximately 6 mi) cross-strike gap between the AK Steel lines and the ODNR-1-88 seismic line suggests the presence of a reverse fault with approximately 792 m (2,600 ft) of estimated vertical displacement. A regional cross section—including the WSU 1990 seismic line eastward of the ODNR-1-88 line—exhibits a faulted west-verging asymmetric syncline in near proximity to the Grenville Front. This cross section also shows that deformation of the Middle Run Formation and the underlying layered sequence exhibits a consistent tectonic style of reverse faulting and folding that developed in response to Grenville Front tectonism.

Fusulines of the Hoyo Oscuro section, Ándara massif of Picos de Europa (Cantabrian Zone, N Spain). New constraints about the onset of the Variscan deformation

The Hoyo Oscuro section (Ándara Massif, southeastern part of Picos de Europa) is a comparatively small exposure of Pennsylvanian syntectonic deposits that shown angular unconformity on the fairly extensive pre-tectonic carbonate platform strata of Pennsylvanian age accumulated in the distalmost realms of the Variscan foreland basin of the Cantabrian Zone. Fusuline-bearing strata from this section yielded species belonging to the genera Pseudostaffella, Ozawainella, Fusulinella, Protriticites, Pseudotriticites, Fusulina and Quasifusulinoides; one of these forms, Protriticites schulzei Villa, is described as a new species from the Cantabrian Mountains. Fusuline assemblages allow us to correlate the Hoyo Oscuro strata with the syntectonic successions of the northern part of Picos de Europa (Gamonedo area) and with specific intervals of the Picos de Europa Formation that, according to currently accepted models, were pre-tectonic. The age data obtained for the oldest syntectonic deposits of the studied section are of key importance, since they constitute a new anchor point confirming the onset of the Variscan Orogeny in this part of the Cantabrian Zone.

Comparison of stratigraphic rock and sedimentary environment of Shemshak formation in Central Alborz: sections Glendrood - Lavij – Vaz, Iran

The study area lockated in the central Allborz whch is in accordance with U shape Caspian Sea. In this Research Shemshak Formtion in the Glandrud region has been Studid and compared in three Section A, B, C in therm Litology Effective Tectonice prossesing in the Formation,Sedementary Environment and Squence of Calasses. These Sections are consisting of sedementry Layer of shemshak Formation, the layer bandray (Elika Formtion & older Formtion) and upper bandray(Lar-Dalichai) in the type section desegnation of shemshak 4 litozone the litilogy of this intity is much more diverse. Sedementry rocks in the studied area are based on desert traps including sandeston types such as quartzit conglomerent, laterite, sub liticarenait, shaillean thin layers and Coal which are Generally Paraconformity or angular unconformity with dolomitic – calcrus cross. on the due to the earlier Cimmerian orogeny phse, carbonate sedimentary environment changed to coal depasetis formation.the UPPER Triassic carbonat rocks in the study area are somtime contain oroganic matte and iron oxide hidroxid of shemshak which formed in the sedementry Environment tidal flats or lagoon. In addition the lateritic section at the base of shemshak formation shows the sedementry discontinuity of the earlier cimmirian land tenure phase.In the section A at the base of shemshak formation is on the part of Laterit Hoeizon but at the upper part bordered Dalichai formation. At th section of B on the in the hillside of Sordar the Lower boundray of Shemshak Formation contain Laterit Hoeizon the form of Paraconformity and is located on Elika Formation but the upper boundary in the form of angular unconformity bordered Dalichai formation. At th section of C lower boundary of shemshak formation does not contain bauxite- laterit and is located on the Elika formation and the upper bandray ends in direction of Dalichai Formation. in term sedimentary environment Dolomit–Limeston formed in the Tidal Flats, Sandeston in the shallow coastal or condition open River and Coal has been depasited castal marsh and sowamp. The bauxite – Laterit horizon are of peneplain type.

STRATIGRAPHIC AND STRUCTURAL RELATIONSHIPS THROUGH GEOLOGICAL AND GAMMAESPECTROMETRY ANALYSIS IN THE INTERFACE BETWEEN THE SÃO FRANCISCO CRATON AND THE ARAÇUAÍ OROGEN (SANTA RITA ANTICLINE, MINAS GERAIS, BRAZIL)

Geological mapping (1:25.000 scale), supported by gammaespectrometric analysis, was conducted in the Santa Rita Anticline region, a regional structure located in the contact between the Araçuaí Orogen external belt and the São Francisco Craton. The work aimed to detail the region's structural and stratigraphic relationships between the rocks of Espinhaço and São Francisco supergroups, which contact is not characterized by a thrust front, as it is in a large part of the Espinhaço Meridional Range (EMR). Five units from Espinhaço were mapped: Galho do Miguel Formation and Conselheiro Mata Group, represented by the Santa Rita, Córrego dos Borges, Córrego Bandeira and Córrego Pereira formations. By its turn, three units from the São Francisco Supergroup were mapped: undivided Macaúbas Group and Bambuí Group, represented by the Serra de Santa Helena and Lagoa do Jacaré formations. Restricted to the Espinhaço units, the Santa Rita Anticline consists in a structure with a south dipping axis and inflections that form saddle structures. The analysis of the gammaespectrometric responses provided clues that were confirmed in the field, highlighting an angular unconformity between the Córrego Pereira Formation and the Macaúbas Group and the local presence of isoclinal folds in Serra de Santa Helena rocks, promoting relevant questions regarding possible intermediary deformational events between the Statherian and Tonian tafrogenesis. The study contributes by raising questions about the evolution of the Araçuaí Belt in its contact with the São Francisco Craton and possible implications imposed by the Paramirim
 Keywords: Aerogeophysics, Litho-structural framework, Fold belt and craton transition, Espinhaço Meridional Range

Continental response to mid-Cretaceous global plate reorganization: Evidence from the Tan–Lu Fault Zone, eastern China

Investigation of the ~2400-km-long Tan–Lu Fault Zone (TLFZ) in eastern China is the key to understanding how the Izanagi Plate in the western Pacific Basin and the East Asian continental margin responded to global plate reorganization during the mid-Cretaceous. We present new structural and geochronological data to show that the central segment of the NNE–SSW-striking TLFZ underwent a phase of sinistral transpression after the Early Cretaceous rifting. The resultant strike-slip structures are ductile shear belts in the south of the segment and brittle faults in the north. Quartz c-axis fabrics and other microstructures indicate deformation temperatures of 350–500 °C in different parts of the shear belts. The brittle faults were associated with the formation of NE–SW-trending folds and an angular unconformity between Lower and Upper Cretaceous volcanic or sedimentary rocks. Fault-slip data indicate that sinistral faulting was the result of NS compression. UPb dating constrains the timing of sinistral faulting between 97 and 82 Ma (early Late Cretaceous). Integration of these and existing data demonstrates that the entire TLFZ underwent sinistral displacement at the beginning of the Late Cretaceous, consistent with continental-scale NS compression in eastern China. Such compression in the overriding plate was caused by rapid oblique subduction of the Izanagi Plate and reflected global plate reorganization at this time. Both the changes in the kinematics of the Izanagi Plate and the resultant variation of stress states in the continental margin around the mid-Cretaceous are ascribed to this plate reorganization.

Unfolding impacts of freaky tectonics on sedimentary sequences along passive margins: Pioneer findings from western Indian continental margin (Offshore Indus Basin)

The Western Passive Continental Margin of the Indian Plate (WCMI) serves as an elegant laboratory for understanding the syn-sedimentary rift-drift tectonics preserving a variety of episodic structural deformations and complex sedimentary infill. Here we present a multidisciplinary study on Offshore Indus Basin (OIB) that is less investigated compared to adjacent marginal basins along WCMI. Reflection seismic, gravity, borehole, and biostratigraphic data have been used to reconstruct the tectono-sedimentary history of the Meso-Cenozoic succession in OIB. Seismic based dynamic stratigraphy helped in mapping seven different depositional sequences grounded on morpho-tectonic considerations. The seismic expression of these sequences provided an idea of the depositional styles with different tectonic episodes since rifting in Jurassic to basin inversion in Miocene continued to present time. The OIB initially filled from the north with the sediments rapidly prograding southwards. In general, the basin deepens in the central and northwestern part where the formations achieve maximum depths. The analysis of 3D structural models revealed that the region experienced poly-phase deformation from the Late Cretaceous to recent times that include steeply dipping normal faults, horst, and graben, half-graben, half-graben with growth faulting, flower structures, anticline, syncline, and uplift with an angular unconformity. The most remarkable tectonic activity happened at the Early Miocene and resulted in the reactivation of extensional faults into strike-slip faults giving rise to a spectacular structural inversion due to transform movement between Indian and Arabian Plates that continues to present day. The most predominant faults are oriented in S20°-50°E with azimuth as 120°–160° and the maximum dip angles are >80° in the southwest flank of the basin. The main fault trend is S20°E-N20°W and dip angles ranging between 40° and 80° and above. A thick crust and the Ocean-Continent Transition (OCT) is imaged with massive felsic, mafic, and ultramafic intrusions by the help of forward gravity modeling. An initial onset of syn-rift tectonic subsidence between 90 and 68 Ma with a post-rift general increase between 68 and 54 Ma is comprehended while two uplift events at ~40 Ma and ~18 Ma are documented through backstripping analysis. It is inferred that the region is rapidly under complex structural inversion with growing folding, faulting, and flowering structures. This study could help in explaining the unanswered reasons of structural complexities, depositional styles, and basin inversion along worldwide passive margins.