Late Cretaceous Paleogene Research Articles

НОВЫЕ ДАННЫЕ О МИНЕРАЛОГИИ, ГЕОХИМИИ И ГЕНЕТИЧЕСКИХ ОСОБЕННОСТЯХ БЕЛОГОРСКОГО МАГНЕТИТОВОГО МЕСТОРОЖДЕНИЯ (СИХОТЭ-АЛИНЬ)

New data are in favor of the view previously substantiated by geological, geochemical and isotopic data that orebodies of the Belogorskoe deposit are metamorphosed and partially regenerated in the Late Cretaceous-Paleogene products of erosion (in the Triassic) of laterite weathering crust of gabbroids. The source for the formation of the Belogorskoe deposit was shown to be products of exogenous destruction of rocks, which by their isotopic and geochemical characteristics are close to the Cambrian gabbroids of the Vladimiro-Alexandrovsky massif (the southern part of the Okrainsko-Sergeevsky terrane). It has been found that the Belogorskoe deposit is composed of rocks and ores, the primary (magmatic) distribution of REE in which was changed to varying degrees as a result of interaction between sediments (protoliths) and seawater (presumably during the Late Jurassic-Early Cretaceous accretion), as well as their metamorphosed analogues and hydrothermal solutions (in the Late Cretaceous-Paleogene). The influence of gabbroids (as a source of matter) on the chemical and mineral composition of the Belogorskoe deposit is consistent with the data reported in the article concerning the enrichment of orebodies in such elements as Fe and Mn that are characteristic of ultrabasic rocks and the presence of Au-Ag-Pd-Pt, Ni-Co and Bi mineralization in them. The orebodies of the Belogorskoe deposit contain accessory minerals and mineral varieties that are rarity in nature and little-studied. These include an unusually rich Th variety of zircon, baddeleyite, gudmundite, a large group of bismuth compounds, including Bi2Te, (Ag,Pb)BiS2, as well as coloradoite, lafossaite, sanbornite, perovskite, and the compound InPO4. There is also a large group of rare and unusual compounds of noble metals: copper gold, platinum gold, jonassonite, disordered solid solutions of Cu, Ag and Au (Au-based), Pt-Pd, Pt-Ag intermetallics, and other rare minerals and mineral varieties.

Geological structure and Mesozoic-Cenozoic tectonic evolution of the Nenya-Chumysh basin (Southern Salair, southern Western Siberia)

Research subject. The Nenya-Chumysh basin is a long-term Mesozoic intracontinental sedimentary basin confined to the zone of a regional fault separating the Salair from the structures of Gorny Altai, Gornaya Shoria, and the Kuznetsk basin. Aim. To establish the geological and structural-kinematic characteristics of impulses of intracontinental orogeny that took place during the Mesozoic and Cenozoic in the territory of the northwestern part of the Altai-Sayan Folded Area. Materials and Methods. Geological maps of the area, geophysical data on the position of the base of the Paleozoic basement, satellite images and digital elevation models were used. The sedimentary filling of the basin is considered as a chronicle of tectonic movements in the NW part of the Altai-Sayan Folded Area at the intracontinental stage of development. Results. The Early Jurassic, Early Cretaceous, Late Cretaceous-Paleogene, and Neogene-Quaternary tectonic stages of the development of the Nenya-Chumysh basin were distinguished. In the Early Jurassic, the Nenya-Chumysh basin was a pull-apart basin in a left-hand strike-slip zone. This stage is associated with the accumulation of coal-bearing deposits of the Glushinskaya Formation, the thickness of which in the Nenya-Chumysh basin reaches about 1900 m. In the Early Cretaceous, as a result of changes in the stress field, the Nenya-Chumysh basin was transformed into a thrust basin, composed of terrigenous deposits of the Ilek Formation, forming a wedge-shaped sedimentary basin characteristic of foreland troughs. The neotectonic structure of the Nenya-Chumysh basin, formed in the stress field of the Indo-Eurasian collision, inherits an older structural plan in general terms, although differing in details. A non-inherited structure is the transverse neotectonic uplift of the Sary-Chumysh swell. Conclusions. The Early Jurassic stage is related with the closure of the Paleo-Tethys and the collision of a series of Cimmerian terranes with the southern margin of Eurasia, Early Cretaceous stage is caused with Mongol-Okhotsk collision, and the Cenozoic stage proceeds with the ongoing Indo-Eurasian collision. The geological evolution of continental sedimentary basins controlled by regional faults can be used as a source of information about the intensity and kinematic pattern of impulses of intracontinental orogeny in the geological past.

Neotethyan Ankara Melange, central Turkey: Formation by accretion of seamounts and supra-subduction zone ophiolites in an oceanic fore-arc setting

The Neotethyan Ankara Melange is a global reference for oceanic accretionary processes preserved in a collisional orogen. Here we show, based on eight representative outcrops around Ankara, that the melange encompasses stratigraphically coherent volcanic-sedimentary successions of mainly Late Jurassic-Early Cretaceous age. Our results indicate that the melange has a relatively organised tectonostratigraphy, in contrast to previous interpretations that emphasised its chaotic nature. Coherent volcanic-sedimentary successions of Late Jurassic-Early Cretaceous age are interpreted as flank facies of a large oceanic seamount (probably plume related) and its capping carbonate platform (atoll), including reef-and back-reef facies. Remnants of other seamounts are dated as Late Triassic-Early Jurassic and Late Cretaceous. Variably dismembered supra-subduction zone ophiolites of latest Early Jurassic-Middle Jurassic age, including boninites, formed in an oceanic fore-arc setting, similar to that of the Cenozoic Izu-Bonin fore arc, NW Pacific. The melange in the Ankara region partly accreted during the Early Cretaceous (pre-Albian) in response to collision of the inferred large seamount with the oceanic (ophiolitic) fore arc. During the collision which involved subduction-erosion slices of proximal–distal seamount flank lithologies accreted sequentially, whereas the seamount core subducted. Also during the collision, the distal outer edge of the ophiolitic fore arc, mainly mantle harzburgite, detached from the over-riding lithosphere and was incorporated into the melange. Structural evidence emphasises the importance of tectonic processes (rather than olistostromes) in the melange accretion. The accretionary prism in the outcrops studied was covered by arc-related sediments and volcanics during the Late Cretaceous and deformed by collision-related processes during latest Cretaceous-Paleogene.

Cretaceous–Paleogene tectonic reconstructions of the South Scotia Ridge and implications for the initiation of subduction in the Scotia Sea

The Cenozoic development of the Scotia Sea and the opening of Drake Passage led to the dispersal of crustal blocks of the North and South Scotia ridges, which today have a strong influence on the pathway of the Antarctic circumpolar current. The pre-translation positions of the crustal fragments of the Scotia ridges are uncertain, with correlations to both the Antarctic and South American plates. We present direct geochronology results ( 40 Ar/ 39 Ar) from the Bruce and Jane banks of the South Scotia Ridge that yield Late Cretaceous–Paleogene ages, indicating a pre-translation magmatic history. The basaltic magmatism from Bruce Bank is calc-alkaline, akin to the Cenozoic magmatism of the South Orkney microcontinent and the South Shetland Islands, and agrees with pre-translation tectonic models that place the crustal blocks of the South Scotia Ridge adjacent to the northern Antarctic Peninsula arc. The intra-oceanic arc magmatism at Jane Bank is Late Cretaceous in age (97.2 ± 1.1 Ma) and is therefore inconsistent with models suggesting a Miocene origin as part of the ancestral South Sandwich arc. The development of westwards-directed subduction adjacent to Jane Bank is predicted in some tectonic models as a consequence of Late Cretaceous plate dynamics that developed prior to the Oligocene–Miocene ancestral arc. Supplementary material: Full 40 Ar/ 39 Ar datasets and GPlates reconstruction files are available at https://doi.org/10.6084/m9.figshare.c.6639909

Implications of multiple fluids in the deposition of Pb-Zn-Ba deposits in the Alvand Mountain, Golpayegan, Iran: Evidence from fluid inclusions and O, C, S isotopes

Middle Cretaceous sedimentary carbonates of Alvand Mountain host Pb-Zn-Ba veins. This mineralization occurs mainly as veins, breccia fillings, and to a lesser extent disseminated and host rock replacements. Ore mineralogy is simple and consists of sphalerite, galena, and barite, with minor pyrite, rare chalcopyrite, and tetrahedrite. Host rock dolomitization and hydrothermal silicification are typically associated with ore. Two types of primary liquid–vapor fluid inclusions were distinguished in sphalerite, quartz, and barite. Type I (salinity, 17–23 wt% NaCl; Th, 130 ± 30 °C) is dominant in sphalerite, whereas type II (salinity, 4.5–10 wt% NaCl, Th, 190 ± 40 °C) is dominant in quartz and barite; these fluids have characteristics of basinal brines and show a negative mixing trend in an evolving process of sulfide and gangue saturation. The δ18O and δ13C values for host rock and altered minerals range from 22.0 to 12.9 ‰ and 3.8 to −3.2 ‰, respectively, which suggest the influence of increased temperature fluids, presence of organic carbon, and fluid mixing. The δ34S values of sulfides and barite varies from 2 to 17 ‰ and 23 to 24 ‰, respectively, suggesting that reduced sulfur could be derived by thermochemical reduction of Paleogene seawater sulfate in the presence of organic matter; however, the wide ranges of δ34S sulfide values (15 ‰) exhibits that reduction of sulfur probably originated by different sulfur reduction processes. The data present in this study suggest that during increased tectonic activity in the late Cretaceous-Paleogene, mixing of basinal brines and water–rock interaction resulted in Pb-Zn-Ba deposition in carbonate host rocks. Therefore, it may represent low-temperature mineralization, possibly analogous to MVT depositional systems.

Late Cretaceous–Paleogene terrestrial sequence in the northern Kitakami Mountains, Northeast Japan: Depositional ages, clay mineral contents, and vitrinite reflectance

AbstractForearc basin deposits on continental margins contain important information that can be used to reconstruct the tectonic setting, volcanism, and climate at the time of their deposition. Coal‐bearing terrestrial to shallow marine strata in Northeast Japan were deposited in a forearc basin along the Eurasian continental margin during the Cretaceous–Paleogene. The rocks exposed in the Kado district, Iwate Prefecture, in the northern Kitakami Mountains include the Upper Cretaceous Yokomichi Formation and the Paleogene Kogawa Group; the latter is known for high‐quality refractory clay (kaolin clay). However, their stratigraphy and sedimentological characteristics are not yet fully understood. To reconstruct the formation and filling of the basin, we investigated field observations, U–Pb dating of tuff samples, XRD analysis of tuff and mudstone samples, and vitrinite reflectance of coal samples in this sequence. The U–Pb ages of the Yokomichi Formation and the Kogawa Group are ∼86 Ma and 58–52 Ma, respectively. The U–Pb age of the kaolin‐dominated tuffaceous rock (“red rocks”) is 56.1 ± 0.2 Ma. The mean random vitrinite reflectance (VRr) ranges from 0.37% to 0.53% through the sequence. We propose the following sequence for the formation and filling of the basin. (1) The basin initially formed during the Coniacian–Santonian (Late Cretaceous) and was filled by fluvial–lacustrine sediment. (2) These sediments kept the shallow burial depths during a ∼28 Myr and made a hiatus (86–58 Ma). (3) The basin was reactivated and covered by tuffs during the Thanetian, and the tuffs were altered to kaolin clay during the Paleocene–Eocene Thermal Maximum. (4) The basin was filled rapidly by alluvial fan deposits and subsided <2300 m (assuming a geothermal gradient of >30 K/km). (5) The basin was uplifted and exhumed at a rate of >50 m/Myr faster than the mean exhumation rate of the Kitakami Mountains since the Paleogene.

Structural inheritance and style within the Getic Depression, South Carpathians, Romania

The Carpathians are part of the Alpine orogen, and the Getic Depression (or Getic fold belt) is located to the south of the South Carpathian. Underthrust beneath the fold belt is the Moesian Platform lower plate. This foreland depocenter can reach a depth of up to 10 km and evolved in an oblique convergent setting from latest Cretaceous-Paleogene and was shortened during the Badenian-middle Sarmatian (middle to late Miocene, 16–8 Ma) and Pliocene to recent. Thus far, in previous publications, the role of the structural grain of the lower plate was poorly constrained. For the fold belt, contrasting interpretations implied a range of shortening magnitudes and contrasting fault pattern. This contribution shows seven balanced cross sections that rely on seismic reflection and well data. One section, just outside and to the south of the fold belt, gives insights into the fault network of the Moesian Platform. In that section we see 35 km of north westward directed normal sense extension that creates a set of rotated fault blocks. Growth strata within the half grabens attest to Permo-Lower Triassic extension age. The individual normal faults merge at depth into a common detachment that rises monotonously towards the east and forms a domal-shaped, arched detachment. This is the structural grain that we project down plunge towards the north beneath the fold belt. The interpreted six sections that lie in the tectonic transport direction show that structures in the western part of the Getic fold belt are compatible with the inversion on the underlying Permo-Lower Triassic extensional fault. Ubiquitous truncation of Oligocene strata by overlying units suggest inversion started during late Oligocene (intra-Burdigalian). The Badenian-Sarmatian shortening further deforms the pre-existing contractional features and the shortening increases from 5 km on the west to at least 17 km on the east. NW-SE oriented transfer zones with normal faults separate the fold belt domains with diverging displacement vectors and eastward increasing shortening. Two main salt levels within the fold belts’ sediment pile are laterally discontinuous hence they only have local significance in the deformation. The frontal part of the fold belt consists predominantly of Badenian-Sarmatian synkinematic units as the fold belt propagated into the foredeep units, this interpretation requires less shortening in the frontal structures compared to earlier solutions. Due to the lack of characteristic features on the studied sections, we infer that the Getic fold belt did not evolve as a transtensional depocenter during the lower Miocene as suggested by earlier publications.

Laramide crustal detachment in the Rockies: Cordilleran shortening of fluid-weakened foreland crust

ABSTRACTWhat causes previously stable continental crust in the forelands of Cordilleran orogenic systems to shorten during low-angle subduction? The National Science Foundation/EarthScope Bighorn Project combined seismic imaging of the crust and Moho with kinematic modeling of Laramide (Late Cretaceous–Paleogene) basement-involved deformation to address this question. In north-central Wyoming, asymmetrical ENE-verging upper-crustal folds are highly discordant with broader, N-trending warps in the Moho, indicating crustal detachment. Restorable cross sections of ENE-directed detachment at a depth of ~30 km, combined a smaller component of NNW–SSE shortening due to the east-narrowing shape of the crustal allochthon, can explain the anastomosing network of Laramide basement-cored arches without major deformation of the underlying mantle lithosphere.Thrust-related fold geometries and west-to-east initiation of deformation in the Laramide and Sevier thrust belts point to Cordilleran end-loading from the west. Differences between Laramide (~N65E) and plate (~N25E) convergence directions, along with the fanning of Laramide shortening directions from nearly E–W to the south to NE–SW to the north, indicate slip partitioning during end-loading west of the Rockies.Sub-horizontal detachment with a near-zero critical taper within cratonic crust suggests an extremely weak Laramide detachment zone during deformation. Analogous lower-crustal deformation in subduction forearcs is associated with slow earthquakes and slab dehydration. We hypothesize that low-angle subduction of the Farallon Plate suppressed fluid-consuming melting and corner-flow processes that characterize higher-angle subduction. This allowed subduction-generated fluids to escape upward into the overlying continental lithosphere, causing retrograde metamorphism and increased fluid pressure that facilitated crustal detachment. This hydration-based hypothesis predicts that crustal detachment will accompany major earthquakes in active analog orogens.

First-Order Stratigraphic Boundaries of the Late Cretaceous–Paleogene Retroarc Foreland Basin in Colombia

The present-day Magdalena Valley, Eastern Cordillera, and Llanos Basin were part of a regional multiphase basin that started as an extensional basin in the Jurassic. Then, it was transformed into a retroarc foreland basin in the Late Cretaceous and subsequently separated into a hinterland and a foreland basin during the late Eocene. We incorporated new data from the Llanos Basin and Eastern Cordillera and chronostratigraphically correlated it with the adjacent basins. Their correlation contributed to establishing the stratigraphic boundaries formed during the first-order changes that marked the beginning and the end of the lifespan of the retroarc foreland basin. In the initial stage, the lateral extent along the dip of the significant depocenter that extended from the Magdalena Valley to the westernmost Llanos Basin was approximately 300–470 km. At the same time, the western flank of the Eastern Cordillera and most of the Llanos Basin were uplifting. The contact between the retrograding marine facies of the Upper Lidita, Buscavidas, Umir, Guadalupe, and Palmichal units marks a late Campanian maximum regressive surface formed during the initial exhumation of the orogen, the Central Cordillera. Therefore, it represents a first-order stratigraphic surface. This surface does not extend across the whole basin. In the uplifting areas, subaerial unconformities truncate the middle Campanian rocks. Their combination represents the lower first-order boundary of the sequence, and their diachroneity is the product of the northward migration of the orogen. The Teruel, Hoyon, Bogota, Cacho, Socha, Barco, and Cuervos formations are truncated by a regional subaerial unconformity. It was formed during orogenic unloading that marks the termination of the foreland basin in the Eocene. As it marks another first-order change, it is the upper boundary of the first-order sequence.

Insights on the late Cretaceous-Eocene event in the Tunisian eastern foreland using subsurface data

Tunisia is characterized by a specific structural location in the northern African margin, related to the geodynamic evolution of the Mediterranean basin. In fact, the Tunisian geological history strongly depends on the relative kinematics of the African-Eurasiatic plates, response to the successive opening of the Tethys and the Mesogea oceans which occurred, respectively, during the late Triassic-Jurassic and the Cretaceous periods. These extensional phases were followed, in the late Cretaceous by a compressive event subject to many controversies among many authors. In order to elucidate this event, a study based on both analysis and interpretation of seismic profiles was achieved in the eastern Tunisian foreland (Sahel and pelagian blocks). It indicates that the late Cretaceous-Eocene compressive event is characterized by NNE-SSW shortening axis and seems to be diachronous. This diachronism results from the resumption of local halokinetic structures throughout the late Cretaceous-Paleogene. The latter were active since the Jurassic-lower Cretaceous then reactivated later through the Senonian extension.

Post-Cretaceous structural reconstruction of the west Central Iranian micro-plate: Insights from structural and magnetic fabrics (AMS) constraints

The Central Iranian Micro-plate (CIM) is a dismembered piece of northern Gondwana. The aim of this study is to reconstruct the post-Early Cretaceous structural evolution of the western edge of CIM in the light of the integration of regional to the micro-scale structural data with minor Anisotropy of Magnetic Susceptibility (AMS) analyses. Our original field measurements on the structural architecture of the study area show main NW-SE and E-W structural trends that are accompanied by structural evidence for superposition. However, paleostresses obtained from fault and fold analysis (stress inversion method on faults and statistically π-plane and β-axis solution on folds), statistical Fry center-to-center analysis on the oriented thin-sections integrated with AMS results suggest that the study area has experienced a NE-SW-directed compressional regime since Paleocene time followed by a post-Early Miocene, roughly N–S-directed, regional compressional regime. Furthermore, the results of this work confirm the consistency between regional-micro structural analysis and AMS analysis. The most of samples show composite (sedimentary + tectonic) magnetic fabric and intermediate arrangement in the orientation of the magnetic fabric. Reconciling our results with published structural and AMS data suggests the changes in the regional stress regime in the western CIM has been occurred in response to the long-term stress transition from the infant Late Cretaceous–Paleogene subduction of the Neo-Tethys Ocean to the mature Cenozoic stages of the Zagros collision and the consequent Neogene tectonic reorganization in the hinterland domains of the southern Eurasian plate.

Progressive Development of a Distributed Ductile Shear Zone beneath the Patagonian Retroarc Fold-Thrust Belt, Chile

Abstract The southern Patagonian Andes record Late Cretaceous–Paleogene compressional inversion of the Rocas Verdes backarc basin (RVB) and development of the Patagonian fold-thrust belt (FTB). A ductile décollement formed in the middle crust and accommodated underthrusting, thickening, and tectonic burial of the continental margin (Cordillera Darwin Metamorphic Complex (CDMC)) beneath the RVB. We present new geologic mapping, quartz microstructure, and crystallographic preferred orientation (CPO) fabric analyses to document the kinematic evolution and deformation conditions of the décollement. Within the CDMC, the décollement is defined by a quartz/chlorite composite schistose foliation (S1-2) that is progressively refolded by two generations of noncylindrical, tight, and isoclinal folds (F3–F4). Strain intensifies near the top of the CDMC, forming a >5 km thick shear zone that is defined by a penetrative L-S tectonite (S2/L2) and progressive noncylindrical folding (F3). Younger kink folds and steeply inclined tight folds (F4) with both north- and south-­dipping axial planes (S4) overprint D2 and D3 structures. Quartz textures from D2 fabrics show subgrain rotation and grain boundary migration recrystallization equivalent to regime 3, and quartz CPO patterns indicate mixed prism <a> and [c] slip systems with c-axis opening angles indicative of deformation temperatures between ~500° and >650°C. Approximately 40 km toward the foreland, the shear zone thins (~1 km thick) and is defined by the L-S tectonite (S2/L2) and tightening of recumbent isoclinal folds (F3). Quartz textures and CPO patterns indicate subgrain rotation recrystallization typical of regime 2 and dominantly basal <a> slip, and c-axis opening angles are consistent with deformation temperatures between ~375° and 575°C. Deformation occurred under greenschist and amphibolite facies conditions in the foreland and hinterland, respectively, indicating that the shear zone dipped shallowly toward the hinterland. The Magallanes décollement is an example of a regional ductile shear zone that accommodated distributed middle to lower crustal thickening below a retroarc FTB.

Metallogenic Evolution of Northeast Asia Related to the Cretaceous Turn of Geological Evolution

This study tests the hypothesis of Cretaceous Turn of Geological Evolution (CTGE). It uses the large dataset on mineral deposits of NE Asia compiled by the US Geological Survey in collaboration with Russian, Mongolian, Korean, and Japanese geological institutions. As predicted, the Triassic–Early Jurassic and Late Cretaceous–Paleogene geodynamic activities in NE Asia were simple, producing a relatively small amount of mineral deposits (94 and 132, respectively). In contrast, the greatly increased geodynamic activity around CTGE produced a huge amount of mineral deposits (288). The Jurassic–Early Cretaceous superplume-related melts were injected into accretionary wedges that formed along the Pacific–Eurasian margins, whereas adakitic and granitic magmas derived from the shallow slab and lower crust were intruded into the huge intracontinental region. The characteristic mineral deposits are represented by the unique Jurassic–Early Cretaceous plume-related Ti-Fe-V (+P + Cr-PGE + Au + diamond) ores. Other CTGE representatives are the porphyry Cu-Mo and Au (+Ag)-vein deposits, which formation, however, continued into the Late Cretaceous–Paleogene epoch. These deposits were generated by the slab- and crust-derived adakitic and granitic melts formed under influence of the expiring superplume and intensifying subduction. The Late Cretaceous–Paleogene epoch is indicated by a decreasing metallogenic activity in general, and an increasing role of subduction-related deposits in particular.

Together but separate: decoupled Variscan (late Carboniferous) and Alpine (Late Cretaceous–Paleogene) inversion tectonics in NW Poland

Abstract. In Europe, formation of the Palaeozoic Variscan orogenic belt, and the Mesozoic–Cenozoic Alpine–Carpathian orogenic belt led to a widespread inversion events within forelands of both orogenic domains. We used legacy 2-D seismic data together with the newly acquired 3-D seismic data that, for the first time, precisely imaged sub-Zechstein (i.e. sub-evaporitic) upper Palaeozoic successions in NW Poland in order to develop a quantitative, balanced 2-D model of the late Palaeozoic–recent evolution of this area, characterised by a complex pattern of repeated extension and inversion. Four main tectonic phases have been determined: (1) Late Devonian–early Carboniferous extension and subsidence possibly related to extensional reactivation of Caledonian thrusts, (2) late Carboniferous inversion caused by the Variscan orogeny, (3) Permo-Mesozoic subsidence related to the development of the Polish Basin and (4) its Late Cretaceous–Paleogene inversion. Variscan and Alpine structures form a superimposed multilayer inversion system, mechanically decoupled by the Zechstein evaporites.

Detrital zircon provenance of the Cretaceous–Neogene East Coast Basin reveals changing tectonic conditions and drainage reorganization along the Pacific margin of Zealandia

Abstract The Upper Cretaceous–Pliocene strata of New Zealand record ~100 m.y. of Zealandia's evolution, including development of the Hikurangi convergent margin and Alpine transform plate boundary. A comprehensive, new detrital zircon U-Pb data set (8315 analyses from 61 samples) was generated along a ~700 km transect of the East Coast Basin of New Zealand. Age distributions were analyzed and interpreted in terms of published data available for Cambrian–Cretaceous igneous and metasedimentary source terranes using a Monte Carlo mixture modeling approach. Results indicate a widespread Early Cretaceous transition in sediment source from the Gondwana interior to the Median Batholith magmatic arc prior to Late Cretaceous rifting from Antarctica. Submergence of Zealandia during a Late Cretaceous–Paleogene drift phase led to major drainage reorganization and the influx of Eastern Province sediment to the East Coast Basin. A long-lived sediment conduit that transported extraregional Western Province detritus to the south-central East Coast Basin may have developed along a structural precursor to the Alpine Fault. Marked Neogene increase of Upper Jurassic–Lower Cretaceous Torlesse Composite Terrane sediment to the central East Coast Basin resulted from exhumation of the Axial Ranges, convergence along the Hikurangi subduction margin, and concurrent development of the Alpine Fault. Concurrent influx of contemporaneous Neogene zircon in the northern East Coast Basin indicated the onset of subduction-related volcanism of the Northland–Coromandel Volcanic Arc. Middle Miocene–Pliocene exhumation and dextral translation of the Nelson region along the Alpine Fault resulted in the eastward routing of Western Province sediment to the central East Coast Basin. Finally, topography developed across the plate boundary and ultimately partitioned continental drainage of Zealandia, such that sediment from the Murihiku, Caples, and Rakaia Terranes in the Otago region was routed to the southern extent of the East Coast Basin. These results illuminate the evolution of the Zealandia continental drainage divide in response to the initiation of the Pacific-Australian plate boundary and demonstrate the power of mixture modeling and large data sets for deciphering sediment routing in dynamic tectonic environments.

Upper Campanian bentonite layers in the Scaglia-type limestone of the northern Dinarides (SE Slovenia)

The research area is located in south-eastern Slovenia and belongs to the eastern extensions of the Slovenian Basin adjacent to the Adriatic Carbonate Platform. The studied section is 25 m thick and consists of grey, brownish and reddish pelagic limestones and calciturbidites, and two bentonite layers 110 and 10 cm thick. Both volcanoclastic horizons consist of greenish, fine-grained muddy material. To date, no other bentonites of similar age are known in the wider Southern Alpine and Dinaridic region. The late Campanian to Campanian/Maastrichtian age of the succession was determined from planktonic foraminifera and calcareous nanoplankton assemblages. XRD analysis revealed the presence of calcite, quartz, muscovite/illite and smectite, which prevails in the clay fraction and is indicative of bentonite clays. We interpret these bentonite horizons as resulting from direct deposition of volcanic ash in a marine environment with a concomitant admixture of detrital material (quartz, muscovite) and later diagenetic carbonatization. The geochemical composition suggests a felsic volcanic origin. The most likely source is the Late Cretaceous–Paleogene bimodal rhyolitic/basaltic volcanism documented along the Sava Suture Zone in present-day Croatia, Bosnia and Herzegovina, Serbia, and North Macedonia. In the Central Apennines three locations with bentonites have been documented. Further spatial and temporal analysis of similar volcanogenic horizons could yield important data on the paleogeographic and tectonic evolution of the Adria/Apulia continental margin.

Mesozoic Intracontinental Orogeny in the Tectonic History of the Kolyvan’– Tomsk Folded Zone (Southern Siberia): a Synthesis of Geological Data and results of Apatite Fission Track Analysis

Abstract —The Kolyvan’–Tomsk folded zone (KTFZ) is a late Permian collisional orogen in the northwestern section of the Central Asian Orogenic Belt. The Mesozoic history of the KTFZ area includes Late Triassic–Early Jurassic and Late Jurassic–Early Cretaceous orogenic events. The earlier event produced narrow deep half-ramp basins filled with Early–Middle Jurassic molasse south of the KTFZ, and the later activity rejuvenated the Tomsk thrust fault, whereby the KTFZ Paleozoic rocks were thrust over the Early–Middle Jurassic basin sediments. The Mesozoic orogenic events induced erosion and the ensuing exposure of granitoids (Barlak complex) that were emplaced in a within-plate context after the Permian collisional orogeny. Both events were most likely associated with ocean closure, i.e., the Paleothetys Ocean in the Late Triassic–Early Jurassic and the Mongol–Okhotsk Ocean in the Late Jurassic–Early Cretaceous. The apatite fission track (AFT) ages of granitoids from the Ob’ complex in the KTFZ range between ~120 and 100 Ma (the Aptian and the Albian). The rocks with Early Cretaceous AFT ages were exhumed as a result of denudation and peneplanation of the Early Cretaceous orogeny, which produced a vast Late Cretaceous–Paleogene planation surface. The tectonic pattern of the two orogenic events, although being different in details, generally inherited the late Paleozoic primary collisional structure of the Kolyvan’–Tomsk zone.

Geodynamics of the Active Margin of Northeast Asia in the Late Cretaceous–Paleogene

Geodynamics of the Active Margin of Northeast Asia in the Late Cretaceous–Paleogene

Tromsø–Bjørnøya Composite Tectono-Sedimentary Element, Barents Sea

Abstract The Tromsø–Bjørnøya Composite Tectono-Sedimentary Element (CTSE) in the southwestern Barents Sea comprises strata of Late Paleozoic–Paleocene age. Since the Paleozoic Caledonian Orogeny, the structural evolution of the CTSE is mainly related to extension, culminating in Late Jurassic–Early Cretaceous hyperextension. Some compressive deformation observed during Late Cretaceous–Paleogene times may relate to activity in the North Atlantic prior to the Early Eocene onset of seafloor spreading between Norway and Greenland. The sedimentary succession may be up to 14 km thick. It comprises Late Paleozoic continental facies, followed by carbonates, evaporites, and eventually cherts and marine clastic material. The overlying Triassic–Paleocene succession is entirely siliciclastic, reflecting Triassic–Middle Jurassic deltaic and shallow-marine conditions followed by deeper-marine conditions during Late Jurassic–Paleocene times. Primary reservoirs are encountered in the latest Triassic–Middle Jurassic succession, with secondary reservoirs found in the Late Jurassic–Early Cretaceous synrift succession, and in Paleocene strata. The primary source rock for petroleum is of Late Jurassic–Early Cretaceous age. Other source rocks include strata of Triassic and Barremian age, and a recently observed unit of Cenomanian–Early Turonian age.

Eagle Foreland Basin Tectono-Sedimentary Element, Yukon Territory, Northwest Canada

Abstract The Eagle Foreland Basin Tectono-Sedimentary Element (TSE) comprises two separate parts: a larger rectilinear sub-basin of Cretaceous age (Eagle Plain) and a smaller fault-bounded mid-Cretaceous–Paleogene sub-basin (Bonnet Plume) in the SE, separated from the Eagle Plain by an inlier of the Ogilvie Platform TSE. Faulted remnants of older Mesozoic clastic strata are locally preserved beneath northern parts of the Eagle Plain Sub-basin. The Eagle Foreland Basin initiated as a Cordilleran foredeep and was incorporated into the orogen during Late Cretaceous–Paleogene deformation. It preserves dominantly marine clastic strata >2500 m thick, with thickest preservation in the NW. Thermal maturity data suggest that 2000–3000 m of deposits were removed by Paleogene erosion. Petroleum potential exists, with principal active sources lying within subjacent successions. The Eagle Plain Sub-basin is an early mature to mature basin, oil and gas prone in the deeper basin, and gas prone in younger units. The Bonnet Plume Sub-basin, known for its coal-bearing strata, is largely unexplored. It contains non-marine to marginal-marine clastic strata, and is considered to be a marginally mature to mature gas-prone basin. The total mean in-place potential in the Eagle Foreland Basin TSE is suggested to be on the order of 20 MMm 3 of oil and 22 000 MMm 3 of gas.