Berriasian Research Articles

Upper Berriasian chemostratigraphy, clay minerals and calcareous nannofossils of the Barlya section (Western Balkan, Bulgaria): Implications for palaeoclimate and productivity changes, and stratigraphic correlations across the Alpine Tethys

Upper Berriasian chemostratigraphic, clay mineral and calcareous nanofossil data are presented from a precisely dated hemipelagic section of Barlya (Western Balkan, Bulgaria). The section covers an interval from the upper part of the lower Berriasian (Calpionella elliptica Subzone, magnetozone M17r) to the lowermost Valanginian (Calpionellites darderi Subzone, magnetozone M14r). The study aims to reconstruct the major palaeoenvironmental changes (variations in lithogenic input, palaeoredox and palaeoproductivity) and their relation to palaeoclimate and regional tectonic regime, as well as their application to stratigraphic correlations with the Vocontian Basin and Jura Mts. A long-term increase in terrigenous input during the late Berriasian was controlled mostly by the orogenic activity in the NeoTethyan Collision Zone and to a lesser degree by climate humidification, as revealed by variations in kaolinite content and in lithogenic proxies (Ti/K, Th/K, Ti/Al and Zr/Rb ratios). A good correlation is observed between geochemical palaeoproductivity proxies (sedimentation rates of non-detrital (excess or authigenic) portions of P, Zn and Cd) and nannofossil fluxes, determined as the total abundance and species richness. Major calcareous nannofossil peaks, represented by high-diversity and high-abundance nannofossil assemblages, fall within the low-productivity intervals. A smaller peak formed by a low-diversity and high-abundance assemblage, dominated by Watznaueria barnesiae/fossacincta, coincides with the variable, but mostly high-productivity interval, which indicates high plasticity of Watznaueria concerning to environmental conditions. Additionally, trophic changes seem to correspond to bulk rock carbon-isotopic composition, with rising δ13Ccarb values in more oligotrophic intervals. This offers perspectives for long-distance chemostratigraphic correlations between pelagic and platform sections, supplementing traditional schemes based on bio- and sequence stratigraphy. A holostratigraphic correlation is proposed between the Western Balkan (Barlya section), Vocontian Basin (Berrias and Monclus sections) and Jura Mts (La Chambotte section) based on bio-, magnetic and carbon-isotope stratigraphy, as well as climatic and palaeoproductivity proxies.

Early Cretaceous charophytes from south Dobrogea (Romania). Biostratigraphy and palaeobiogeography

Eleven boreholes and one outcrop of the Lower Cretaceous in South Dobrogea (south-eastern Romania) were sampled for charophytes. Twenty species are described and illustrated in two non-marine rock units, the Zăvoaia Member and the Gherghina Formation. The Zăvoaia Member contains a charophyte assemblage dominated by Feistiella bijuescensis, aff. Mesochara harrisii, Nodosoclavator bradleyi, Clavator bilateralis, and Clavator grovesii var. grovesii, indicating a Berriasian age. Other less abundant species include Feistiella sp., Latochara sp., Mesochara dobrogeica sp. nov., Globator maillardii var. nurrensis, Atopochara trivolvis var. micrandra, Clavator grovesii var. discordis, Hemiclavator adnatus, and Hemiclavator neimongolensis var. posticecaptus. The occurrence of G. maillardii var. nurrensis in this assemblage suggests late Berriasian age. The Gherghina Formation is dominated by the species Atopochara trivolvis var. triquetra and Clavator grovesii var. jiuquanensis. Other less abundant species include Sphaerochara andersonii, aff. Mesochara harrisii, Globator maillardii var. trochiliscoides, Globator maillardii var. biutricularis, Clavator harrisii var. reyi, and Clavator ampullaceus var. latibracteatus var. nov. This assemblage indicates a late Barremian–early Aptian age. This study sheds new light on the palaeobiogeographical distribution of Lower Cretaceous charophytes in the Tethyan realm. Well-known western European charophyte species such as F. bijuescensis, S. andersonii, G. maillardii var. trochiliscoides, H. adnatus, and H. neimongolensis var. posticecaptus are herein described for the first time in eastern Europe. Very significantly, this is the first report in Europe of the hitherto North American taxon C. bilateralis, while the species C. ampullaceus has previously been reported only from the Middle East and eastern Africa.

A lost carbonate platform deciphered from clasts embedded in flysch: Štramberk-type limestones, Polish Outer Carpathians

Limestones designated the Štramberk-type are the most common carbonate exotic clasts (exotics) embedded in the uppermost Jurassic–Miocene flysch deposits of the Polish Outer Carpathians. About 80% of stratigraphically determinable carbonate exotics from the Silesian, Sub-Silesian and Skole units (nappes) are of Tithonian (mostly)–Berriasian (sporadically Valanginian) age. A study of these exotics revealed eight main facies types: coral-microbial boundstones (FT 1), microencruster-microbial-cement boundstones (FT 2), microbial and microbial-sponge boundstones (FT 3), detrital limestones (FT 4), foraminiferal-algal limestones (FT 5), peloidalbioclastic limestones (FT 6), ooid grainstones (FT 7), and mudstones-wackestones with calpionellids (FT 8). Štramberk-type limestones in Poland and the better known Štramberk Limestone in the Czech Republic are remnants of lost carbonate platforms, collectively designated the Štramberk Carbonate Platform. Narrow platforms were developed on intra-basinal, structural highs (some of them are generalized as the Silesian Ridge), with their morphology determined by Late Jurassic synsedimentary tectonics. An attempt was made to reconstruct the facies distribution on the Tithonian–earliest Cretaceous carbonate platform. In the inner platform, coral-microbial patch-reefs (FT 1) grew, while the upper slope of the platform was the depositional setting for the microencruster-microbial-cement boundstones (FT 2). Microbial and microbial-sponge boundstones (FT 3), analogous to the Oxfordian–Kimmeridgian boundstones of the northern Tethyan shelf (also present among exotics), were developed in a deeper setting. In the inner, open part of the platform, foraminiferal-algal limestones (FT 5) and peloidal-bioclastic limestones (FT 6) were deposited. Poorly sorted, detrital limestones (FT 4), including clastsupported breccias, were formed mainly in a peri-reefal environment and on the margin of the platform, in a high-energy setting. Ooid grainstones (FT 7), rarely represented in the exotics, were formed on the platform margin. Mudstones-wackestones with calpionellids (FT 8) were deposited in a deeper part of the platform slope and/or in a basinal setting. In tectonic grabens, between ridges with attached carbonate platforms, sedimentation of the pelagic (analogous to FT 8) and allodapic (“pre-flysch”) Cieszyn Limestone Formation took place. The most common facies are FT 4 and FT 1. Sedimentation on the Štramberk Carbonate Platform terminated in the earliest Cretaceous, when the platform was destroyed and drowned. It is recorded in a few exotics as thin, neptunian dykes (and large dykes in the Štramberk Limestone), filled with dark, deep-water limestones. Reefal facies of the Štramberk Carbonate Platform share similarities in several respects (e.g., the presence of the microencrustermicrobial-cement boundstones) with reefs of other intra-Tethyan carbonate platforms, but clearly differ from palaeogeographically close reefs and coral-bearing facies of the epicontinental Tethyan shelf (e.g., coeval limestones from the subsurface of the Carpathian Foredeep and the Lublin Upland in Poland; the Ernstbrunn Limestone in Austria and Czech Republic). Corals in the Štramberk Limestone and Štramberk-type limestones are the world’s most diverse coral assemblages of the Jurassic–Cretaceous transition. The intra-basinal ridge (ridges), traditionally called the Silesian Cordillera, which evolved through time from an emerged part of the Upper Silesian Massif to an accretionary prism, formed the most important provenance area for carbonate exotic clasts in the flysch of the Silesian Series. They are especially common in the Lower Cretaceous Hradiště Formation and the Upper Cretaceous–Paleocene Istebna Formation. The Baška-Inwałd Ridge and the Sub-Silesian Ridge were the source areas for clasts from the Silesian and Sub-Silesian units (e.g., in the Hradiště Formation), while the Northern (Marginal) Ridge was the source for clasts from the Skole Unit (e.g., in the Maastrichtian–Paleocene Ropianka Formation).

The proposal of a GSSP for the Berriasian Stage (Cretaceous System): Part 2

In part 1 of this work we discussed the possibilities for the selection of a GSSP for the Berriasian Stage of the Cretaceous System, based on prevailing practical methods for correlation in that J/K interval, traditional usage and the consensus over the best boundary markers that had developed in the last forty years. This consensus has developed further, based on the results of multidisciplinary studies on numerous sites over the last decade. Here in Part 2 we give an account of the application of those results by the Berriasian Working Group (ISCS), and present the stratigraphic evidence that justifies the selection of the locality of Tré Maroua (Hautes-Alpes, SE France) as the proposed GSSP. We describe a 45 m-thick section in the Calcaires Blancs vocontiens – that part of the formation covering the calpio­nellid Chitinoidella, Remanei. Intermedia, Colomi, Alpina, Ferasini, Elliptica and Simplex biozones. The stratigraphic data collected here has been compiled as part of a wider comparative study of complementary Vocontian Basin sites (with localities at Charens, St Bertrand, Belvedere and Le Chouet). Evidence from Tré Maroua thus sits in this substantial regional biostratigraphic and magnetostratigraphic context. For the purposes of the GSSP definition, here we particularly concentrate on the unbroken sequence and biotic markers in the interval immediately below the boundary, the Colomi Subzone (covering circa 675,000 years), and immediately above, the Alpina Subzone (covering circa 725,000 years). Particularly significant fossil datums identified in the Tré Maroua profile are the primary basal Berriasian marker, the base of the Alpina Subzone (a widespread event marked by dominance of small Calpionella alpina, with rare Crassicollaria parvula and Tintinopsella carpathica): the base of the Berriasian Stage is placed at the base of bed 14, which coincides with the base of the Alpina Subzone. Secondary markers bracketing the base of the Calpionella Zone are the FOs of the calcareous nannofossil species Nannoconus wintereri, close below the boundary, and the FO of Nannoconus steinmannii minor, close above. The Tithonian/Berriasian boundary level occurs within M19n.2n, in common with many documented sites, and is just below the distinctive reversed magnetic subzone M19n.1r (the so-called Brodno reversal). We present data which is congruent with magnetostratigraphic and biostratigraphic data from other key localities in France and in wider regions (Le Chouet, Saint Bertrand, Puerto Escaño, Rio Argos, Bosso, Brodno, Kurovice, Theodosia…), and thus the characteristics and datums identified at Tré Maroua are key for correlation and, in general, they typify the J/K boundary interval in Tethys and connected seas.

Slump/Slide facies and biostratigraphy at the transition of the Cieszyn and Hradiste formations in the Cieszyn (Tesin) Section (Outer Flysch Carpathians)

ABSTRACT: New sedimentological observations in the Lower Cretaceous of the Silesian Unit and integrated biostratigraphy based on calcareous nannofossils, dinoflagellate cysts, calpionellids and foraminifers have brought new insight to the stratigraphy of the Cieszyn section. The oldest exposed strata of themudstone facies of the Cieszyn Limestone Formation are of early Berriasian age, based on calcareous nannofossil evidence. This work proposes that the Jurassic-Cretaceous boundary reported by previous authors was based on reworked microfossils. The detritic facies of the Cieszyn Limestone Formation, typically dominated by detritic-limestone turbidites, appears to be completely missing. Instead, a thick body with combined slump and slide features, of Berriasian–Valanginian age, forms the transition with the overlying lower Valanginian strata of the Hradiste Formation. The slump/slide body represents a local facies, deposited on a fault scarp related to fault-controlled extension of the Proto-Silesian Basin floor.

Lowermost Cretaceous limestones from the Kučaj zone (Carpatho–Balkanides, Eastern Serbia): new data on their age assignment

The lowermost Cretaceous carbonate deposits of the Carpatho–Balkanides (Eastern Serbia), which crop out in the Kučaj zone, were studied in three sections: Kamenica, Prekonozi and Jerma River Canyon. The identified micropalaeontological assemblages generally consist of calcareous green algae (mainly dasycladaleans), benthic foraminifera (mainly orbitolinids, cyclaminids, pfenderinids), and scarce calpionellids. The dasycladalean algal association comprises mostly species known from the Berriasian–lower Valanginian. The same age is also indicated by the majority of the identified benthic foraminifera, except for the orbitolinids from the upper parts of the sampled successions that hitherto were only known from the upper Hauterivian–lower Aptian of Southern France and Northern Spain. The co-occurrence of Berriasian–lower Valanginian algae and benthic foraminifera with Hauterivian–Aptian orbitolinids challenges establishment of the age of the sampled succession and, potentially, other carbonate successions too. The recognition of rare calpionellid specimens in samples containing orbitolinids can resolve this dilemma. Calpionellids are planktonic microfossils with a well-defined stratigraphic distribution within the Neotethyan realm; consequently, the identified species belonging to the Calpionellopsis zone confirm a late Berriasian age. In addition, it should be emphasized that some of the orbitolinids known until now only from upper Hauterivian–lower Aptian deposits were already present in the studied region from the base of the upper Berriasian.

First computer-assisted 3D-reconstruction of calpionellid tests (Protozoa incertae sedis) and corresponding section restoration

Calpionellids are widespread protozoans of Late Jurassic-Early Cretaceous age, typically found in Tethyan pelagic domains and related paleobiogeographic provinces. Their abundance and rapid evolution make them excellent biochronological markers as they are considered by the Berriasian Working Group of the ICS's International Subcommission on Cretaceous Stratigraphy as primary tools for fixing a GSSP to the base of the Berriasian stage (Jurassic-Cretaceous boundary). Regarding the calpionellid entire morphology studies, attempts of their chemical extraction from carbonated matrix are very scarce and, therefore, available 3-D morphologies are very limited. Hence, these microfossils are mostly studied in thin sections where they are randomly cut, leading to apparent variations among representatives of an individual taxon. Therefore, their taxonomy, phylogeny and related biozonations are still subject to divergent interpretations. This work proposes a first Computer-Assisted method for 3D-reconstruction of calpionellid loricae based on published axial sections. It also allows the simulation of all possible random cuts and to visualize corresponding apparent sections. Parametric 3D designs and restored sections can be defined (and stored) in Cartesian coordinate systems that respect the natural proportions of the studied tests. This leads to a more objective systematic paleontology of calpionellid section, a preliminary guide towards updating calpionellid phyletic relationships and biozonation schemes. Beyond calpionellids, our methodology may generate further ideas and alternative digital tools for micropaleontologists and paleontologists working on thin sections, leading to improvements in fossil determinations and taxonomical studies. • New Computer-aided methodology for 3D reconstruction of calpionellid tests • Simulation of calpionellid sections • This helps: 1) approaching a more objective systematic paleontology of calpionellid sections; 2) updating biostratigraphy and phylogeny • The proposed methodology may generate further ideas for micropaleontologists to improve some fossil section taxonomical studies.

Bivalve Mollusks from the Lower Berriasian Deposits of the Northern Slope of the Ai-Petri Yaila (Southwestern Crimea)

Five bivalve species (Arcomytilus sanctaecrucis, Neithea valangiensis, Plagiostoma dubisiensis, Prohinnites renevieri, and Protocardia broili sp. nov.) are described from a new locality in Southwestern Crimea. These species, along with the gastropod Phaneroptyxis broili and the foraminifer Bramkampella arabica, indicate the Early Berriasian age of the carbonate deposits examined. The transition zone between the Upper Tithonian and the Lower Berriasian was identified in one of the sections.

Early Cretaceous sea-level changes and major palaeoclimate events in the Northeastern Peri-Tethys

The Early Cretaceous quantitative sea-level curve constructed for the epeiric basin of the Eastern Russian Platform (Northeastern Peri-Tethys) is based on the results of facial analysis and quantitative paleo-depth assessment. The detailed evaluation of the Early Cretaceous sea-level cycles results in recognition of the sea-level and climate changes as controlling factors on depositional environments in the basin. Major climatic events are identified by the comparison between the global and regional sea level curves. “The cold snaps” coincide with simultaneous global and regional sea level lowstands, peak shallowing and the almost complete absence of strata. The Late Berriasian and Late Aptian “cold snaps” were identified in the Eastern Russian Platform. The Lower Aptian bituminous shales are interpreted as being a regional manifestation of the OAE 1a. The forcing mechanism behind this OAE is an abrupt rise in temperature.

The Huncal Member of the Vaca Muerta Formation, Neuquén Basin of Argentina: Insight into biostratigraphy, structure, U-Pb detrital zircon ages and provenance

In the western sector of the Neuquén Basin, the organic-rich shales of the Vaca Muerta Formation are intercalated with turbidite sandstone intervals and slump structures integrated in the Huncal Member. The age of the Huncal sandstones based on the integration of the ammonite faunas, calcareous nannofossils and U-Pb analysis is late Berriasian in their type locality. The origin of this deposit is probably related with two lobes of turbiditic sandstones linked with a progradational regressive phase. Sandstones are lithic arkoses and feldspathic litharenites derived from recycled orogenic and dissected arc sources. The U-Pb ages confirm a mixed sedimentary provenance from the south and southeastern margins of the basin, specifically from Paleozoic and Triassic–Jurassic rocks of the North Patagonian Massif and the Huincul High. The complex fold and fault system described in the sandstone levels was interpreted as the result of slump processes with a main transport direction to the SW and W. Sandstone deposits with slump structures assignable to the Huncal Member are present throughout the entire basin from the Tithonian to the Valanginian in the Vaca Muerta Formation. Therefore, the Huncal Member is a diachronic lithostratigraphic unit and its deposition probably depended on different factors such as relative sea level changes, the position in the ramp system or in the platform and slope configuration and internal morphostructural features of the Neuquén Basin.

The proposal of a GSSP for the Berriasian Stage (Cretaceous System): Part 1

Here in the first part of this publication we discuss the possibilities for the selection of a GSSP for the Berriasian Stage of the Cretaceous System, based on the established methods for correlation in the Tithonian/Berriasian interval. This will be followed, in the second part, by an account of the stratigraphic evidence that justifies the locality of Tre Maroua (Hautes-Alpes, SE France) as the proposed GSSP. Here we discuss the possibilities for correlation in the historical J/K boundary interval, and the evolution of thinking on the positioning of the boundary over recent generations, and in relation to research in the last ten years. The Tithonian/Berriasian boundary level is accepted as occurring within magnetosubzone M19n.2n. The detailed distribution of calpionellids has been recorded at numerous sites, tied to magnetostratigraphy, and the base of the calpionellid Alpina Zone is taken to define the base of the Berriasian Stage. This is at a level just below the distinctive reversed magnetic subzone M19n.1r (the so-called Brodno reversal). We discuss a wide range of magneto­stratigraphic and biostratigraphic data from key localities globally, in the type Berriasian areas of France and wider regions (Le Chouet, Saint Bertrand, Puerto Escano, Rio Argos, Bosso, Brodno, Kurovice, Theodosia etc.). The characteristic datums that typify the J/K boun­dary interval in Tethys and its extensions are detailed, and the correlative viability of various fossil groups is discussed. The boundary level is correlated to well-known J/K sections globally, and a series of secondary markers and proxies are indicated which assist wider correlation. Particularly significant are the primary basal Berriasian marker, the base of the Alpina Subzone (marked by dominance of small Calpionella alpina, Crassicollaria parvula and Tintinopsella carpathica) and secondary markers bracketing the base of the Calpio­nella Zone, notably the FOs of the calcareous nannofossil species Nannoconus wintereri (just below the boundary) and the FO of Nannoconus steinmannii minor (just above). Notable proxies for the boundary are: 1) the base of the Arctoteuthis tehamaensis Zone in boreal and subboreal regions, 2) the dated base of the Alpina Subzone at 140.22 ±0.14 Ma, which also gives a precise age estimate for the system boundary; and 3) the base of radiolarian “unitary zone” 14, which is situated just above the base of the Alpina Subzone.

Organic Geochemistry and Microfossils of the Upper Jurassic and Lower Cretaceous Strata in the Lower Reaches of the Olenek River (Northeastern Framing of the Siberian Platform, Arctic Siberia)

Abstract —The organic-geochemistry data reveal two levels in the reference Upper Jurassic–Lower Cretaceous section of the lower reaches of the Olenek River: lower (Volgian–lower Boreal Berriasian (diasterene)) and upper (Boreal Berriasian–Valanginian (hopane)). The Volgian beds are composed of clays with abundant prasinophytes Leiosphaeridia and Tasmanites and various dinocyst assemblages and have the highest content of organic carbon (Corg), up to 9%. Isoprenoids, in particular, pristane and phytane, are highly predominant among aliphatic hydrocarbons; their content is more than three times higher than that of coeluting n-alkanes, which is typical of buried chlorophyll-containing plankton (dinocysts and prasinophytes). Sedimentological, biofacies, and paleoecological analyses show that the highly carbonaceous beds of the Buolkalakh Formation formed under oxygen deficit conditions. An integrated analysis demonstrated that the pristane/phytane ratio does not always reliably reflect the reducing or oxidizing conditions of organic-matter accumulation and diagenesis. The discrepancy between the geochemical identification of organic matter according to the pristane/phytane ratio and the biofacies and sedimentological data is due to the low catagenetic maturity of OM. The Volgian was marked by a significant transgression of the Anabar–Lena sea, which was gradually changed by a successive regression of its basin at the end of this stage and in the Boreal Berriasian. The Corg contents in the coastal and subcontinental sediments decreased. Diasterenes and 4-methyldiasterenes disappeared from the balance of biomarker molecules, and the portion of hopanoids increased. Aerobic environments prevailed in the subbottom waters. Earlier, three biomarker horizons were identified according to geochemical criteria in the synchronous sections of Anabar Bay (Laptev Sea coast): terpane, diasterene, and hopane ones. In the section of the Olenek basin, the upper two horizons are well identified by specific biomarkers, and the lower one is absent because of the sedimentation break. Stratigraphic analysis of the location of these geochemical levels in different parts (and bathymetric zones) of the Anabar–Lena basin shows their diachronous formation. According to all geological and geochemical criteria, the Volgian Stage and the lower beds of the Boreal Berriasian Stage of this basin have a high petroleum potential. In the axial zone of the basin and, especially, on the Laptev Sea shelf, there were probably favorable conditions for the generation and accumulation of hydrocarbons genetically related to the Upper Jurassic highly carbonaceous rocks.

New belemnite records from the Mitarai Formation, Tetori Group, Japan: Delimitation of the Jurassic-Cretaceous boundary in the Japanese Islands

Traditional faunal elements for zoning the uppermost Jurassic‒lowermost Cretaceous stratigraphic interval in Tethyan regions, i.e., ammonites and calpionellids, are either lacking in the boreal regions at that time, or are of generally low diversity and endemic compositions. Consequently, recognition of Jurassic-Cretaceous boundary interval sections has been hindered in many areas of the boreal regions, as well as some lower latitude intermediate areas, such as the Japanese Islands.Strata of the Mitarai Formation of the Tetori Group of central Japan have previously provided ammonites suggesting a broadly Tithonian–Berriasian age for the formation, but the Jurassic-Cretaceous boundary, nor the boundary interval, have never been precisely identified in it, due to the poorly preserved nature of the faunas and their endemic nature. We have recognized a fauna of belemnites from a locality of the Mitarai Formation, including Cylindroteuthis knoxvillensis Anderson, C. knoxvillensis?, C.? sp., Arctoteuthis tehamaensis (Stanton), A. cf. tehamaensis, A. cf. repentina Saks & Nal'nyaeva, and Acroteuthis? sp. Collectively, this belemnite assemblage of the Mitarai Fm indicates the interval of the Jurassic-Cretaceous boundary, as recognized at northern Siberia (Russia) and northern California (USA), and is thus the first certain identification of this boundary in the Japanese Islands. The Mitarai Fm belemnite assemblage can be used to establish the presence of the Jurassic-Cretaceous boundary interval in other areas of the Japanese Islands.

Jurassic to Cretaceous (upper Kimmeridgian–?lower Berriasian) calcispheres from high palaeolatitudes on the Antarctic Peninsula: Local stratigraphic significance and correlations across Southern Gondwana margin and the Tethyan realm

We report Upper Jurassic–Lower Cretaceous (Kimmeridgian-Berriasian) calcispheres from the Ameghino (Nordenskjöld) Formation at high palaeolatitudes on the northern part of the Antarctic Peninsula. The Ameghino Formation generally contains a relatively poorly preserved association of calcispheres, which are often recrystallized or replaced by silica; however, early-diagenetic calcite concretions are widespread in the mudstone–tuff sequences, and calcisphere in these contexts show very good preservation. Among the seventeen species recognized in this study, thirteen are known from the Upper Jurassic–Lower Cretaceous pelagic sediments of the Tethyan and Andean regions. The remaining three include Stomiosphaera, and two new species, that probably indicate an austral character for the calcisphere association. The following calcisphere zones previously proposed for the Tethyan realm and the Andes are confirmed for the Ameghino Formation: Carpistomiosphaera borzai, Carpistomiosphaera tithonica, Parastomiosphaera malmica, Colomisphaera tenuis, Colomisphaera fortis and Stomiosphaerina proxima. Zones indicate a late Kimmeridgian to early Berriasian age, broadly consistent with previous age assignments based on ammonites and radiolarians. However, calcisphere ages allow partial stratigraphic re-arrangement of the succession cropping out in Sobral Peninsula and support the intercalation of sandy-conglomeratic beds, deposited in submarine fan environment, between the slope-basinal facies typical of the Ameghino Formation. Facies changes suggest basin margins across the Antarctic Peninsula in a complex paleogeography with large emergent landmasses to the southwest of the study area. Possible dispersal routes along the Southern Gondwana margin occurred along the so-called Hispanic and Mozambique corridors. Identified species show a global distribution, being represented in the Andean, the Tethyan and Boreal realms. The cosmopolitan character of Mesozoic calcispheres proves their importance for interregional correlations.

Ammonite biostratigraphy and bioevents in the Jurassic – Cretaceous boundary of central Chile

Ammonites are abundant and well preserved in the Tithonian-Valanginian (Upper Jurassic – Lower Cretaceous) sedimentary successions of the central Chilean Andes, known as the Lo Valdés and Baños del Flaco Formations. A total of 1429 ammonites were collected from these stratigraphic units and the following index zones based on ammonites are here proposed, from base to top: Virgatosphinctes mexicanus/Pseudolissoceras cf. zitteli, Windhauseniceras internispinosum, Micracanthoceras microcanthum/Corongoceras alternans, Substeueroceras koeneni (Berriasella fraudans and Groebericeras rocardi sub-zones) and Thurmanniceras thurmanni/Argentiniceras fasciculatum.Our analyses indicate that “Ammonite Richness” is high in the middle and upper Tithonian and into the lower Berriasian part of the succession, but decreases towards the lower Valanginian. Highest similarity values are established for the upper Tithonian, coincident with a high diversity; similarity declines in the lower Berriasian. The main faunal turnover occurred between the early and late Berriasian followed by a secondary bioevent between the late Berriasian and early Valanginian.

The dawn of the Cretaceous Period in the English South Midlands

The Early Cretaceous (probably Berriasian – Valanginian) Whitchurch Sands Formation of Oxfordshire and Buckinghamshire, English South Midlands, was deposited as coastal-marine and alluvial sediment along the northern edge of the Wessex Basin. The type succession at Whitchurch in Buckinghamshire includes a marine horizon, probably of Berriasian age. Alluvial sediments dominate the formation elsewhere and are tentatively linked to mid-Valanginian uplift of the nearby London – Brabant Massif. The Valanginian alluvial plain is thought to have bordered a coastal lagoon and barrier complex, accounting for non-marine faunas in the Whitchurch Sands Formation, and limiting seawater influx into the Weald Basin of south-east England, from a South Midlands seaway. Detrital and palaeobiological data from the Whitchurch Sands Formation and type Wealden (Weald Basin) suggests a connection between the seaway and the East Midlands Shelf, through much or all of the Valanginian – early Aptian interval.

Late Jurassic–Early Cretaceous climate change record in clay minerals of the Norwegian-Greenland Seaway

The humid climate of northwestern Europe during the Late Jurassic–Early Cretaceous was punctuated by a widespread arid phase. There are few well constrained and complete sections that document this climate shift from semi-humid to arid, and back to more humid conditions. Detrital clay minerals formed in soils and derived through weathering may be used as palaeoclimatic proxies, and here, clay mineral assemblages from several well-constrained sections from the Norwegian Continental Shelf are presented as a N-S transect of the Norwegian-Greenland Seaway. Palaeoclimate signals in most of the clay mineral sections are complicated by diagenetic overprinting. Yet, towards the Boreal realm of the Norwegian-Greenland Seaway there is a discernible palaeoclimatic signal in the clay mineralogy of Well 16/3–4. At ~30°N, kaolinite is known to have reappeared in the clay mineralogical record in the upper part of Calpionellid Zone B (early-mid Berriasian). However, we find an absence of kaolinite at ~40°N in Well 16/3–4 from the North Sea until the late Berriasian, suggesting that initiation of the first humid phase in the Early Cretaceous Norwegian-Greenland Seaway was diachronous.

Biostratigraphy and microfacies of the pelagic carbonate formations in the Yavorets section (Tithonian–Berriasian), Western Balkan Mts, Bulgaria

Calpionellid study has provided new evidence of early and late Tithonian age of the top of the Gintsi Formation, and of late Tithonian and early Berriasian age of the Glozhene Formation in the Yavorets section (Western Balkan Mts, Bulgaria). The calpionellid Chitinoidella, Praetintinnopsella, Crassicollaria, and Calpionella zones have been documented in successive order. Three calcareous dinocyst zones – Colomisphaera tenuis, Colomisphaera fortis and Stomiosphaerina proxima, have been determined in this lower Tithonian to lower Berriasian interval. From the base upwards, the following microfacies have been recognized: Saccocoma (Gintsi Formation, lower and upper Tithonian), Globochaete alpina, and calpionellid (Glozhene Formation, upper Tithonian and lower Berriasian). The base of the Berriasian has been traced at the explosion of the uniformly shaped spherical variety of Calpionella alpina. Evolutionary lineages of species of the genus Calpionella are discussed, as well as the vertical distributions and abundance peaks of crassicollarians. The calpionellid zones described herein are correlated with coeval zonations from the Western, Central and Eastern Tethyan domains. The regional correlation with previously studied sections of Tithonian/Berriasian pelagic carbonates in the Western Balkan Mts revealed a transition to hemipelagic deposition of the limestone-marl succession of the Salash Formation and/or sandstone accumulation during the middle to late Berriasian (Elliptica and Simplex calpionellid subzones) due to unstable conditions of the sedimentary environment. From the west to the east in the Western Balkan Unit (i.e., from the Rosomač section in eastern Serbia to the Sarbenitsa, Bov and Yavorets sections in the Iskar River Valley area), there is a trend of slight progressive deepening of the basin. This is manifested in the occurrence of redeposited shallow-carbonate-platform microfossils in the west to greater thickenesses of the Gintsi and Glozhene formations and occurrence of sandstone channel deposits in the east.

Notas sobre el contexto tectonoestratigráfico de formación de las esmeraldas colombianas

The geological explorations carried out by the Colombian Geological Survey (SGC, in Spanish) between 2005 and 2008 show that the potential areas for exploration and exploitation of emeralds in the Western Emerald Belt (CEOC, in Spanish) are closely related to the Muzo (Hauterivian-Barremian age) and Rosa Blanca (Valanginian age) geological formations, and in the Eastern Emerald Belt (CEOR, in Spanish), are associated to the Santa Rosa and Chivor formations (Berriasian age). Mineralization is associated with various mesoscopic tectonic structures with hydrothermal alteration.

Integrated stratigraphy and palaeoenvironment of the Berriasian peri-reefal limestones at Štramberk (Outer Western Carpathians, Czech Republic)

A high-resolution multidisciplinary study of two profiles in the Kotouč Quarry at Štramberk was carried out to define the age and palaeoenvironmental setting of the peri-reefal Štramberk Limestone. Calpionellids of the Alpina and Ferasini subzones of the standard Calpionella Zone confirm an early Berriasian age for both studied sequences. The presence of the calcareous nannofossils Nannoconus kamptneri minor and ?Speetonia colligata supports this stratigraphic interpretation. An ammonite assemblage with Pseudosubplanites grandis was found corresponding to the upper part of the lower Berriasian (Grandis Subzone). Foraminiferan assemblages contain several taxa previously reported from the Valanginian. Magnetostratigraphy verifies that the studied sections span the magnetozones M18r to M18n. Rock magnetic measurements indicate magnetite as the carrier of characteristic remanent magnetization. A palaeolatitude suggested location at 36°N. Microfacies indicate palaeoenvironments of slope (FZ 4), platform margin reefs, sand shoals (FZ 5, FZ 6) and possibly patch-reefs in the inner platform (FZ 7). The presence of calpionellids and the polychaete Terebella lapilloides suggests deposition within the deeper parts of the outer ramp of a platform slope, with redeposited clasts derived from nearby reef slopes and/or talus. This research contributes to the Berriasian Working Group's efforts to define the Tithonian–Berriasian boundary.