For over ten years, the Lower to Upper Tithonian boundary beds cropping out in the Owadów–Brzezinki quarry have yielded numerous fossils of ammonites, bivalves, brachiopods, xiphosurans, decapods, insects, and vertebrates – including actinopterygian fishes and various reptiles and others, all of which exhibit fine preservation of their anatomical details due to special environmental conditions during their fossilization. The Owadów–Brzezinki section is also important for stratigraphical correlations because it contains ammonite faunas indicative of the NE European and NW European Subboreal zonal schemes, as well as Tethyan calpionellids. The whole faunal as- semblage, which represents taxa of many iconic groups of Mesozoic animals, has created the opportunity to establish the ‘Owadów– Brzezinki geopark’, a geoeducation area where the public, and especially the young, can learn about the beauty of the natural history of the region.
The study of the Tithonian and lower Berriasian succession of Le Saix (Hautes-Alpes, France) has made it possible to better characterize the lithological succession at a former Berriasian GSSP candidate, its set of microfacies, the stratigraphic ranges of the main groups of marine plankton and therefore the calpionellid and saccocomid biozonations. On the lithological level, the Tithonian strata are characterized by thick-bedded breccias representing debris flows and related calciturbidites, whereas the Berriasian strata are typically white limestones. The lower part of the Berriasian is comprised of scattered intercalations of thin-bedded breccias and calciturbitides (including cryptic mud calciturbidites). In thin sections, the white limestones display mud- to wackestone textures and their allochems are mostly tiny bioclasts (e.g., radiolarians, calpionellids, saccocomids). Calciturbidites have wacke- to grainstone textures and their allochems are mostly pseudointraclasts and extraclasts, comprising various bioclasts and some ooids. Mud turbidites are made of micrograin-stones some yielding almost exclusively well-sorted calpionellids, which were previously erroneously interpreted as the signature of “explosions” or “blooms” of Calpionella alpina. Breccias are mostly lithoclastic floatstones with a matrix similar to that of the calciturbid- ites. Their lithoclasts are either extraclasts sensu stricto, i.e., material derived from updip shallow-water areas, or pseudointraclasts representing reworked subautochthonous material, i.e., mud- and wackestone lithoclasts with radiolarians, saccocomids and/or calpionellids. Radiolarians are common over the whole studied interval. Saccocomids are part of the dominating biota reported from the lower and lower upper Tithonian interval whereas calpionellids replace them in the uppermost Tithonian to lower Berriasian interval. Minor plank- tonic groups comprise calcareous dinoflagellates and Globochaete alpina; Iranopsis nov. group is also present. Intervals with saccocomid sections characteristic of zones 4-5 and zone 6 are respectively ascribed here to the lower Tithonian (4-5) and the lower upper Tithonian (6). The biozonation of the calpionellid group sensu lato allows identification of i) the Boneti Subzone of the chitinoidellids, ii) the Cras- sicollaria Zone, more specifically its Tintinnopsella-Intermedia (A1), Intermedia-Alpina (A2) and Brevis-Massutiniana (A3) subzones, and iii) the Alpina Zone, with its Alpina-Parvula (B1) and its Alpina-Remaniella (B2) subzones. On the basis of biostratigraphical and sedimentological data, most zonal boundaries prove to be hiatal, located at the erosional base of breccia or turbidite layers whereas the Tithonian/Berriasian stage boundary appears to be located at a strike-slip fault plane in the Tré Maroua section.
The Late Jurassic aspidoceratoid genus Pseudhimalayites Spath is scarcely recorded but widely distributed in the Andean basins, the Caribbean region, and in the European Tethys. From Ponti Zone (Lower Tithonian) rocks of the Betic Range in Carchelejo we describe here the new species Pseudhimalayites carchelejensis, based on a macroconch (female) holotype. The corresponding microconch (male), described from the same ammonite assemblage, would belong to the morphogenus Simocosmoceras Spath which groups the microconchs of Pseudhimalayites. P. carchelejensis n. sp. differs from the coeval Pseudhimalayites steinmanni (Haupt) by lacking ventral tubercles in the phragmocone and by bearing umbilical tubercles only from the adult whorl of the phragmocone. These differences illustrate a significant morphologic divergence between the Andean and the Tethyan lineages.
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The key aspect for evaluation of potential effects of ongoing environmental changes is identification of their controlson one hand, and understanding of their mutual relations on other. In this context, the best source of information about medium and long term coThe key aspect for evaluation of potential effects of ongoing environmental changes is identification of their controlson one hand, and understanding of their mutual relations on other. In this context, the best source of information about medium and long term consequences of various environmental processes is the geologic record. Numerous different-scale palaeoenvironmental events took place during the Jurassic/Cretaceous transition; amongst them, the best documented so far are: long term marine regression during the Tithonian-early Berriasian, climate aridization during the late Tithonian-early Berriasian, and tectonic activity in western parts of the Neo Tethys Ocean during the late Berriasian-Valanginian. This study, which is based on the Ph Ddissertation of Damian Gerard Lodowski, attempts to reconstruct the latest Jurassic-earliest Cretaceous paleoenvironment and its evolution in the area of the Western Tethys, with special attention paid to cause-and-effect relationships between climate changes, tectonic activity and oceanographic conditions (perturbations in marine circulation and bioproductivity). Here are presented the basic results of high-resolution geochemical investigations performed in the Transdanubian Range (Hárskút and Lókút, Hungary), High-Tatric (Giewont, Poland) and Lower Sub-Tatric (Pośrednie III, Poland) series, Pieniny Klippen Belt (Brodno and Snežnica, Slovakia; Velykyi Kamianets, Ukraine) and Western Balkan (Barlya, Bulgaria) sections. The sections were correlated and compared in terms ofpaleoredox conditions (authigenic U), accumulation of micronutrient-type element (Zn) and climate changes (chemical index of alteration, CIA), providinga consistent scenario of the Tithonian-Berriasian palaeoenvironment evolution in various western Tethyan basins. Amongst the first-order trends and events, characteristic of studied sections are the two intervals recording an oxygen deficient at the seafloor: 1) the upper Tithonian-lowermost Berriasian (OD I); and 2) at the lower/upper Berriasian transition (OD II). Noteworthy, this phenomena cooccurred with elevated accumulations of nutrient-type elements (i. e. enrichment factor of Zn). Besides, collected data document the late Tithonian-early Berriasian trend of climate aridization, as well as the late Berriasian humidification. Such record is explained by a model, in which decreasing intensity of atmospheric circulation during the late Tithonian-early Berriasian was directly connected with climate cooling and aridization. This process resulted in lesser efficiency of up- and/or downwelling currents, which induced sea water stratification, seafloor hypoxia and perturbations in the nutrient-shuttle process during the OD I. On the other hand, the OD II interval may correspond to tectonic reactivation in the Neo Tethyan Collision Belt. This process might have led to physical cutoff of Alpine Tethys basins from the Neo Tethyan circulation (both atmospheric and oceanic), driving the limited stratification in the former, and limiting the effect of gradual humidification of global climate (i.e. due to increasing strength of monsoons and monsoonal upwellings). nsequences of various environmental processes is the geologic record. Numerous different-scale palaeoenvironmental events took place during the Jurassic/Cretaceous transition; amongst them, the best documented so far are: long term marine regression during the Tithonian-early Berriasian, climate aridization during the late Tithonian-early Berriasian, and tectonic activity in western parts of the Neo Tethys Ocean during the late Berriasian-Valanginian. This study, which is based on the Ph Ddissertation of Damian Gerard Lodowski, attempts to reconstruct the latest Jurassic-earliest Cretaceous paleoenvironment and its evolution in the area of the Western Tethys, with special attention paid to cause-and-effect relationships between climate changes, tectonic activity and oceanographic conditions (perturbations in marine circulation and bioproductivity). Here are presented the basic results of high-resolution geochemical investigations performed in the Transdanubian Range (Hárskút and Lókút, Hungary), High-Tatric (Giewont, Poland) and Lower Sub-Tatric (Pośrednie III, Poland) series, Pieniny Klippen Belt (Brodno and Snežnica, Slovakia; Velykyi Kamianets, Ukraine) and Western Balkan (Barlya, Bulgaria) sections. The sections were correlated and compared in terms ofpaleoredox conditions (authigenic U), accumulation of micronutrient-type element (Zn) and climate changes (chemical index of alteration, CIA), providinga consistent scenario of the Tithonian-Berriasian palaeoenvironment evolution in various western Tethyan basins. Amongst the first-order trends and events, characteristic of studied sections are the two intervals recording an oxygen deficient at the seafloor: 1) the upper Tithonian-lowermost Berriasian (OD I); and 2) at the lower/upper Berriasian transition (OD II). Noteworthy, this phenomena cooccurred with elevated accumulations of nutrient-type elements (i. e. enrichment factor of Zn). Besides, collected data document the late Tithonian-early Berriasian trend of climate aridization, as well as the late Berriasian humidification. Such record is explained by a model, in which decreasing intensity of atmospheric circulation during the late Tithonian-early Berriasian was directly connected with climate cooling and aridization. This process resulted in lesser efficiency of up- and/or downwelling currents, which induced sea water stratification, seafloor hypoxia and perturbations in the nutrient-shuttle process during the OD I. On the other hand, the OD II interval may correspond to tectonic reactivation in the Neo Tethyan Collision Belt. This process might have led to physical cutoff of Alpine Tethys basins from the Neo Tethyan circulation (both atmospheric and oceanic), driving the limited stratification in the former, and limiting the effect of gradual humidification of global climate (i.e. due to increasing strength of monsoons and monsoonal upwellings).
Field magnetic susceptibility (MS) and gamma ray spectrometry (GRS) measurements were performed in the Jurassic/Cretaceous boundary interval in the Tré Maroua section (SE France). The 24 m thick section covers the interval from the upper Tithonian magnetozone M20n (Chitinoidella Zone) to the lower Berriasian M17r magnetozone (Calpionella elliptica Subzone). The micritic limestones reveal a very low content of terrigenous impurities (0.0-0.2% K and 0.2-2.0 ppm Th) and low MS values (-5 to 15 × 10-6 SI). Despite low intensity of both MS and GRS signal, a consistent trend of terrigenous input is observed: decreasing values in the upper Tithonian and increasing tendency in the upper part of the lower Berriasian. The long-term trends are quite similar to those documented in some Western Tethyan sections and the Polish Basin, indicating that variations of terrigenous input might be controlled by large-scale palaeoclimatic variations and relative sea-level changes. Decrease of Conusphaera and increase of Nannoconus frequencies fall in the lower part of M19n2n in the uppermost Tithonian. These events correlate with large decrease of terrigenous input and widespread oligotrophication in the Western Tethyan domain.
This is an account of finds of stratigraphically useful calcareous nannofossils and the magnetostratigraphy of the Jurassic-Cretaceous boundary interval of the eastern Crimean peninsula (southern Ukraine). We compare these new complementary results with those presented by our team in earlier publications. A missing interval in the Crimean sequence is filled, and the position of the Tithonian-Berriasian (J/K) boundary is confirmed.
11 specimens of large sized ammonites from the Štramberk Limestone deposited in the collections in Prague represent 6species. Two species belong to the superfamily Lytoceratoidea, the remaining ones to the superfamily Perisphinctoidea. The perisphinctid specimens belong to the Lower and the Upper Tithonian, and the lytoceratids probably correspond to the same stratigraphic level. Two species, namely Ernstbrunnia blaschkei and Djurjuriceras mediterraneum were not known from the Štramberk Limestone earlier.
Numerous fully cored boreholes completed in the last years in central Poland (Kleszczów Graben area, southern border of the Łódź Depression) enabled the researchers to obtain new sedimentological data on the Oxfordian-Tithonian continuous sedimentary record in the Polish part of the northern Tethys shelf. Twenty-two facies were distinguished in the sedimentological succession. The facies represent the outer-, mid- and inner-ramp environments, including evaporitic episodes and palaeosols. The facies document that the Oxfordian-Lower Kimmeridgian (up to Hypselocyclum) carbonate ramp has evolved to the Upper Kimmeridgian-Tithonian carbonate-siliciclastic ramp. Among the Kimmeridgian deposits, numerous hardgrounds, tidal channel deposits and gravity flow sediments were identified. The Kleszczów Graben sedimentary succession is discussed along with the lithostratigraphical units known from the adjacent regions of southern and central Poland.
In the Cerro Mallín Quemado area (Sierra de la Vaca Muerta) the three members of the Vaca Muerta Formation (Portada Covunco, Los Catutos and Pichi Moncol) can be recognized, including the whole of the Tithonian rock-record. The ammonite fauna does not show significant differences with respect to that of the nearby locality Pampa Tril, but the record of faunal horizons is patchier. Eighteen species of ammonites were recorded through the studied sections, covering the whole of the Andean Tithonian. The current chronostratigraphic zonation of the Andean Tithonian is briefly discussed, updated and correlated with the most recent literature. From the current succession of ammonite bio-horizons previously defined in the basin, only three (picunleufuense alpha, picunleufuense beta and falculatum) were recognized definitely. Four other bio-horizons (perlaevis, erinoides, internispinosum alpha and vetustum) were recognized only tentatively, because the typical assemblages of morphotypes (morpho-species) were not clearly or completely recognized. The current regional time-correlation chart dated by the ammonite bio-horizons of the Neuquén Basin along a 70°W transect is updated with the results of the present study and additional information recently obtained from other localities
The ammonite fauna of the Tithonian–Berriasian of the Vaca Muerta Formation in Pampa Tril has been recently described in detail. New important specimens and additional information are presented in this paper. The phyletic evolution of Choicensisphinctes, passing from C. platyconus to C. erinoides is confirmed, as well as the sexual dimorphic correspondence of this latter with C. mendozanus. A microconch of the genus Krantziceras is described for the first time. New specimens of Substeueroceras koeneni identical to the paralec¬totype, along with material already described from the koeneni Hz. (Koeneni Zone), point to the fixation of this horizon as the type horizon of the species. New specimens of Subthurmannia boissieri from the Damesi Zone match clearly the range of variation of this species in Spain, thus providing an element for time-correlation with the Tethyan standard scale. Additional material from the internispinosum alpha Hz. confirms the origin of W. internispinosum from C. proximus by the inception of an evolutionary innovation in the juvenile ontogeny.
Tithonian (= “Middle Volgian”) carbonate rocks are exposed in Owadów-Brzezinki quarry 19 km southeast of Tomaszów Ma-zowiecki, central Poland. In the upper part of the Sławno Limestone Member, chitinoidellids have been identified in thin sections from three samples, only. Therefore, the documented part of the Chitinoidella Zone in Owadów-Brzezinki quarry is about 0.3 m thick. The identified chitinoidellid taxa suggest that this assemblage represents the Upper Tithonian Boneti Subzone. The Chitinoidella Zone occurs at the top of Unit I and correlates with the uppermost interval of the Zarajskensis Horizon (Matyja, Wierzbowski, 2016). Other microfossils identified in the Chitinoidella Zone consist of Saccocoma sp. and benthic foraminifera of the genus Planularia. Calcareous dinoflagellate cysts (Cadosina semiradiata semiradiata Wanner and C. cf. semiradiata semiradiata Wanner) occur above the chitinoidellid assemblage, in the strata corresponding to the Gerassimovi Subzone of the Virgatus Zone (Matyja, Wierzbowski, 2016). Calcareous nannofossils are extremely rare in the thin sections studied; only one small specimen was seen, identified as Rhombolithion minutum (Rood et al., 1971) Young et Bown 2014. In contrast, microbial filaments are frequently observed in the studied thin sections. Their shape and pattern are reminiscent of some recent Cyanobacteria of the order Nostocales, however the Tithonian microbial filaments are much thinner.
Here we briefly report the discovery of new, exceptionally well-preserved Late Jurassic (Tithonian) fossils from Owadow- Brzezinki quarry - one of the most important palaeontological sites in Poland. These finds which comprise organisms living originally in different environments indicate that the Owadow-Brzezinki site represents a link - most probably in a form of open marine passages - betweeen distinct palaeobiogeographical provinces. This creates an unprecedented opportunity for better recognition of the regional palaeobiogeography of adjacent European areas during the Late Jurassic.
The Tithonian ammonite succession at the Owadów–Brzezinki quarry, central Poland shows the presence of Subboreal ammonites of both NE European (“Volgian”) and NW European (“Bolonian–Portlandian”) affinity, making possible the correlation between the relevant ammonite subdivisions. The former are represented by Zaraiskites – Z. regularis Kutek and Z. zarajskensis (Michalski) as well as an early form of Virgatites – V. gerassimovi Mitta which enable the recognition of the upper part of the Scythicus Zone (the Zaraj¬skensis Subzone) and the lower part of the Virgatus Zone (the Gerassimovi Subzone) of the “Middle Volgian”. The latter are represented by Virgatopavlovia, which enables the correlation with the Fittoni Zone of the uppermost “Bolonian”, and by still younger assemblage of small-sized virgatitids – such as V. pusillus (Michalski), showing similarity to Progalbanites albani (Arkell) of the Albani Zone of the lowermost “Portlandian”. The new species established include: Zaraiskites lewinskii sp. nov. which represents a new member of the virgatitid lineage linking an older Z. pommerania (Arkell) with younger small-sized Virgatites, as well as two species of the genus Virgatopavlovia – V. janeki sp. nov. and V. dembowskae sp. nov. The appearance of ammonites of NW and NE European affinity in central Poland resulted from the opening of the new sea routes possibly related with tectonic activity in northern European areas at the transition from Early to Late Tithonian.
Recent discoveries of ammonites in the Štramberk Limestone in the type area of their occurrence near the town of Štramberk supplement existing data on the Tithonian age of the limestones. Franconites cf. fascipartitus occurs in the lower part of the Lower Tithonian (Neochetoceras mucronatum Zone). Lemencia ciliata has a zonal character in the upper part of the Lower Tithonian. Richterella richteri is a subzonal species of the upper part of the Lower Tithonian in the Mediterranean and Submediterranean areas (Semiformiceras fallauxi Zone). All of the new discoveries are referable to the faunal associations of the Submediterranean bioprovince, and are in agreement with existing knowledge of it. Sexual dimorphism was seen in the genus Richterella, with the recognition of both macroconchs and microconchs in the type species of Richterella, i.e. R. richteri. The stratigraphic position of these recent ammonite discoveries in the Štramberk Limestone at the Kotouč Quarry does not support the stratigraphy of the limestones based on the distribution of calpionellids, as previously assumed by other authors. The recent collection of ammonites confirms that the Štramberk Limestone belongs to the lower Tithonian and lower Berriasian and also represents the lower Tithonian as a shallow-water facies.
A calpionellid zonal scheme is proposed for the Tithonian through Valanginian pelagic carbonates of the Western Balkan Unit, based on the vertical ranges of 57 chitinoidellid and calpionellid species recognized. This zonal scheme consists of calpionellid zones that are widely accepted in the Mediterranean Realm, such as the zones of Chitinoidella, Praetintinnopsella, Crassicollaria, Calpionella, Calpionellopsis, Calpionellites and Tintinnopsella. Subzonal divisions are comparable to those in the Carpathians. Direct correlations between ammonite and calpionellid ranges suggest that the base of the Upper Tithonian corresponds to the FO of Chitinoidella boneti; that of the Upper Berriasian to the FO of the genus Calpionellopsis; and the base and top of the Lower Valanginian to the FO and LO of the genus Calpionellites respectively. Correlations of the calpionellid zonation in the study area with zonations in other areas are discussed.
The studied corals have been collected from cores of boreholes located in the central part of the Polish Carpathian Foreland in the Dąbrowa Tarnowska–Szczucin area. The Jurassic complex in this area presents a continuous stratigraphic section from the Upper Callovian to Tithonian, locally passing to the Lower Cretaceous (Berriasian). Its thickness exceeds 1,100 m in this area. This complex is composed of marine, mainly shallow-water deposits. The corals occur within the upper part of the Upper Jurassic (Tithonian) deposits, almost entirely within the Swarzów Limestone Formation (= coral-algal limestone formation). This occurrence marks the northernmost extent of Tithonian shallow-water corals in Poland and one of the northernmost in Europe. 42 coral species (among them 14 in open nomenclature) were identified in deposits of this formation. They include two new species: Complexastrea magna and Complexastrea dabroviensis. All taxa, except one, belong to the order Scleractinia. The described assemblage displays a Late Jurassic character. The broader stratigraphic span is assigned to some species, which are quoted from the Middle Jurassic and some species lasted until the Early Cretaceous, Berriasian and/or Valanginian.
Magnetostratigraphy is an important method in regional and worldwide correlations across the Jurassic/Cretaceous boundary. The M-sequence of magnetic anomalies, embracing this boundary, provides an easily recognizable pattern which might be identified in biostratigraphically calibrated land sections. The polarity chrons between M21r and M16n are well correlated to calpionellid and calcareous nannofossil stratigraphy in the Tethyan Realm. This results in a very high precision of stratigraphic schemes of pelagic carbonates (ammonitico rosso and maiolica limestones), integrating the two groups of fossils with magnetostratigraphy. The main clusters of the reference sections are located in the Southern Alps and Apennines, but the database was recently enriched by sections from the Western Carpathians and Eastern Alps. Quite a few Jurassic/Cretaceous boundary sections with magnetostratigraphy are known in the Iberian Peninsula and south-eastern France but their importance relies on the integration of magnetostratigraphy also with the Tethyan ammonite zonation. Correlation of Boreal and Tethyan regions still remains a major problem. Just two sections with reliable correlation to the global polarity time scale are documented outside Tethys: a shallow marine to non-marine Tithonian–Berriasian–Valanginian sequence in southern England (Portland–Purbeck beds) and the marine clastic Upper Tithonian–Middle Berriasian (= Middle Volgian–lowermost Ryazanian) sequence at Nordvik Peninsula (Siberia). The Volgian/Ryazanian boundary at Nordvik seems to be located in the lower part of magnetochron M18n, while the most commonly accepted definitions of the Tethyan Jurassic/Cretaceous boundary are situated either within magnetochron M19n (A/B calpionellid zonal boundary, Durangites/Jacobi ammonite zonal boundary), or at the boundary of M19n/M18r (Jacobi/Grandis ammonite subzonal boundary).
Górnojurajskie utwory formacji wapieni koralowcowo-glonowych ze Swarzowa, występujące w środkowej części przedgórza Karpat, w rejonie Dąbrowy Tarnowskiej–Szczucina, zawierają liczne makroskamieniałości (m.in. skleraktinie, mszywioły, ramienionogi, algi) oraz niezbyt liczne mikroskamieniałości. Niektóre mikroskamieniałości są interesującymi wskaźnikami biostratygraficznymi. Występujące sporadycznie w wyższej części tej formacji kalpionellidy (Calpionella alpina, C. aff. alpina, Crassicolaria cf. brevis, Tintinopsella cf. carpatica) wskazują na późnotytoński wiek tych osadów (zona Crassicollaria). Być może, do tytonu należy prawie cała formacja ze Swarzowa i najniższa część leżącej wyżej formacji wapienno-dolomitycznej, muszlowcowej ze Smęgorzowa. Wyższa część formacji ze Smęgorzowa może należeć już do kredy dolnej, do beriasu.
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The Upper Jurassic coral-algal Swarzów Formation in the Dąbrowa Tarnowska–Szczucin area, occuring in the middle part of the Carpathian Foreland Poland contains rich macrofossils (i.e. scleractinian corals, bryozoans, brachiopods, algae) and generally sparse assemblages of microfossils. Some of the latter are interesting as a biostratigraphical tool. Thus, the presence of rare calpionellids (Calpionella alpina, C. aff. alpina, Crassicolaria cf. brevis, Tintinopsella cf. carpatica) argues for Late Tithonian age (standard Crassicollaria zone) of the upper part of this formation. It is suggested that the Swarzów Limestone Formation almost entirely represents the Tithonian, which probably reaches the lowest part of the lithostratigraphic unit of the Smęgorzów Limestone-Dolomitic Coquina Formation. The upper part of this unit may belong to the Lower Cretaceous, to Berriasian.
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In comparison with the Spanish sections, first appearance (FAD) of the Tithonian Nannoconus species is recorded earlier in the Pieniny Klippen Belt and the Western Tatra Mountains (Western Carpathians). The Early Tithonian Nannoconus compressus Zone correlates with the uppermost part of the "Pulla-Tithonica" Zone and the lower part of the Malmica Zone. The N. infans Zone corresponds to the upper part of the Malmica Zone and the lower part of the Chitinoidella Zone (Dobeni Subzone) including the lowermost interval of the Boneti Subzone. The N. wintereri Zone is equivalent to the uppermost part of the Chitinoidella Zone, entire Crassicollaria Zone, and the basal interval of the Berriasian Alpina Subzone. In the Kryta Valley section (Tatra Mts), the Infans/ Wintereri zonal boundary is located within the Boneti Subzone and is correlated with the lower part of the CM20n magnetozone. Specimens referred to Nannoconus sp. A occur in the studied sections; these specimens differ from the published descriptions of all previously established Tithonian species. In the Lower Tithonian limestones nannoconids are scarce being more numerous in the lower interval of the N. wintereri Zone. Increase in abundance of the genus Nannoconus correlates with the Mid- to Late Tithonian Nannofossil Calcification Event (NCE) reported from the Central Atlantic Ocean.
The Hith Formation forms the youngest lithostratigraphic unit of the Jurassic Shaqra Group. It represents the culmination of a succession of hypersaline and euryhaline cycles that characterise the Late Jurassic of Saudi Arabia. The Formation is poorly exposed in central Saudi Arabia, but it has been studied in detail in subsurface eastern Saudi Arabia where the upper carbonate member hosts an important hydrocarbon reservoir called the Manifa Reservoir. Chronostratigraphic control is absent from the formation itself, and the Tithonian age is suggested for the Hith Formation based on its stratigraphic position between the underlying Arab Formation of Late Kimmeridgian age, and the overlying Sulaiy Formation, of Late Tithonian to Berriasian age. The Hith Formation needs redefining in the light of new lithological evidence, and a tripartite member scheme is suggested. This includes the lower anhydrite-dominated member here termed the “anhydrite” member, and considered to represent hypersaline subaqueous deposition within a restricted deep lagoon during the lowstand systems tract of the Manifa sequence. A “transitional“ member consists of interbedded anhydrites and carbonates and approximates with the transgressive zone. The overlying “carbonate” member represents the results of a prograding shallow, normal salinity marine succession related to the highstand systems tract. Interbedded carbonates within the evaporites are interpreted to represent superimposition of a higher frequency, possibly 4th order eustatic cyclicity. The “carbonate“ member hosts the Manifa Reservoir, and here proposed as the Manifa Member, consist of five parasequences, each of which represents a shoaling-upwards cycle with a succession of up to five repeated lithofacies and biofacies that commences with a stromatolitic, microfaunally-barren unit followed by fine-grained grainstones with a monospecific but abundant ostracod biofacies. A succession of coarse pelloidal grainstones with rare foraminifera, including Redmondoides lugeoni, Trocholina alpina with a variety of unidifferentiated valvulinids and miliolids then follows, that passes vertically into coarse ooid grainstones, with rare Redmondoides lugeoni, forming the uppermost part of each parasequence.
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