Biostratigraphic Research Articles

New biostratigraphic data from the Ladinian pelagic limestones of Pizzo di Sant'Otiero - Madonie Mountains, Sicily

New biostratigraphic data, based on conodont investigations, were collected from the Ladinian limestones recently described at Sant’Otiero, a locality near the Village of Petralia Sottana in the Madonie Mountains (Central-Northern Sicily). At this locality a new calcareous succession lying at the base of a major tectonic unit of the Maghrebian chain is described. This succession consists of a lower massive part formed by a carbonate megabreccia, the elements of which are shallow water extraclasts with dasycladalean algae ( Diplopora annulatissima Pia), benthic foraminifers, “ Tubiphytes ” and problematic organisms commonly described from Anisian carbonate platforms. Upward a well-bedded succession of dark-gray Daonella -bearing calcilutites follows. The presence of the bivalve Daonella tyrolensis Mojsisovics in a Lumachella bed from the upper part of the calcilutites can be related to the ammonoid Protrachyceras longobardicum Zone, upper Ladinian in age (lower Longobardian). Upward a sharp contact(decollement?) with the typical sediments of the Mufara Formation can be observed. A re-sampling of the Daonella -bearing calcilutites for conodont investigation has been carried out in order to better constrain the age of this succession. The distribution of conodont species such as Budurovignathus hungaricus (Kozur & Vegh), B. mungoensis (Diebel) and Paragondolella trammeri (Kozur) among other conodonts, permits the correlation of the succession to the P. gradleri and P. archelaus ammonoid Zones, extending downwards the age of the calcilutites at Sant’Otiero to the upper Fassanian. This confirms that the Sant’Otiero succession is a key section to document Ladinian pelagic carbonate sedimentation in the westernmost termination of the Ionian Tethys.

High resolution ammonite–benthic foraminiferal biostratigraphy across the Aalenian–Bajocian boundary in the Lusitanian Basin (Portugal)

This work describes the ammonite and benthic foraminiferal assemblages recorded across the Aalenian–Bajocian boundary of the Serra da Boa Viagem II section, located about 6 km to the east of the Bajocian GSSP (Murtinheira, Portugal), and calibrated to the standard ammonite zonation previously established for the Lusitanian Basin. A total of 220 ammonite specimens referred to 30 fossiliferous levels were collected and identified throughout the section, enabling the recognition of the Concavum Zone (Concavum and Limitatum subzones) of the upper Aalenian, and the Discites Zone of the lower Bajocian. A total of 2356 foraminifers were obtained from the 16 samples collected along the section, corresponding to 4 suborders, 8 families, 16 genera and 44 species.The occurrence of Lenticulina quenstedti (Gümbel) has enabled the recognition of the Lenticulina quenstedti Zone, ranging from the Bradfordensis Zone (middle Aalenian) to the lower Discites Zone (lower Bajocian). The first record of Ramulina spandeli Paalzow, whose occurrence, up to now, was limited in the Lusitanian Basin to the Murtinheira section (the Bajocian GSSP), highlights the usefulness of the Ramulina spandeli Zone, with its lower boundary referred to the lower Discites Zone (lower Bajocian). Other bioevents displaying local, basinal or regional biostratigraphic interest have also been identified.The benthic foraminiferal record here presented, accurately calibrated with the ammonite record, aims at contributing to support the recognition of the Lenticulina quenstedti Zone and the Ramulina spandeli Zone as formal biostratigraphic units integrating the biostratigraphic scale based on benthic foraminifers for the Aalenian–Bajocian boundary in the Lusitanian Basin (Portugal). Copyright © 2014 John Wiley & Sons, Ltd.

Introduction to calcareous algae in Esfiyukh Mountain

In this research the biostratigraphy in Esfiyukh Mountain (5km of North-east of Torbat-e-Heydarieh) is studied for the first time. Thedeposits in this section are about 175 meters thickness; lithology consists ofalternative layers of medium bedded to very thick bedded limestone. This partoverlies on brown-dark red sandstone & Jurassic deposits with angularunconformity and is overlain by late Cretaceous sediments with unconformablecontact. The first study of benthic foraminifera and calcareous algaeidentification is the survey of paleoecology condition of benthic foraminifera,that 60 thin sections were studied. In this study ten genera and species ofcalcareous algae Salpingoporella cf. parapiriniae (Carras et al., 2006),Cylindroporella sp. (Elliot, 1979), Rajkella sp. (Dragastan & Bucur, 1993),Neomeris cretaceous (Stewmann, 1978), Triploporella sp. (SRIVASTAVA, 1978),(BUCUR, 1993), (Granier et al., 2000), Terquemella sp. (Radoicic, 1978),Boueina sp., Macroporella sp., Falsolikanella danilovae, (Radiocic ex1982), (Berger,1992)ag.,Actinoporellageredeensis, (CONRAD,1970), Salpingoporella aff. hasi, ,(Carras et al, 2006) has been known. With view to association ofbenthic foraminifera the age of the studied section Barremian t-Aptian isdetermined.

When did India-Asia Collide and Make the Himalaya?

Critical evaluation and comparison of the available geological and geochronological data from the northern parts of the Himalaya and Trans-Himalaya mountains highlight that these mountains did not initially evolve by the collision of continents of the Indian and Asian plates. Instead, subducted Tethyan oceanic lithosphere in front of the Indian continent melted to produce the calc-alkaline suite of the Shyok-Dras volcanic arc and the Ladakh batholith. Hence, the Indian plate initially subducted beneath and started building up the then existing intra-oceanic island arc. Timing of the first impingement of the Indian and Asia plates has been better constrained at around 57.5 Ma by comparing (i) the bulk ages from the Ladakh batholith (product of partial melting of the Tethyan oceanic lithosphere) with (ii) the subducted continental lithospheric and UHP metamorphosed Indian crust in the Tso Morari, and (iii) biostratigraphy of the youngest marine sedimentation in Zanskar. Thus, the Himalaya witnessed its first rise and emergence from deeply exhumed terrain in the Tso Morari after around 53 Ma, followed by sequential imbrication of the Indian continental lithosphere and associated exhumation during rise of the Himalayan mountains from north to the south since 45 Ma.

AGE AND GEOCHEMISTRY OF BASALT-CHERT ASSOCIATIONS IN THE OPHIOLITES OF THE IZMIR-ANKARA MÉLANGE EAST OF ANKARA, TURKEY: PRELIMINARY DATA

In this paper, we present the preliminary data on the age of the radiolarian cherts deposited on top of basalts belonging to the Eastern Ankara Melange (part of the Izmir-Ankara Melange). Petrological studies on the basalts were carried out in order to constrain the tectonic setting of the studied basalt-chert sequences. Nine sections were sampled East of Ankara and twenty seven samples were collected for biostratigraphic and geochemical analyses. The oldest radiolarian cherts dated in the present paper are referable to the Late Triassic (Section 6: late Norian) and are associated with basaltic rocks of OIB character. OIB type volcanic rocks are also found in other sections, associated with cherts of Late Jurassic (Section 3: middle-late Oxfordian to late Kimmeridgian-early Tithonian) and Early Cretaceous (Section 1: late Valanginian to late Hauterivian) ages. E-MORB type rocks are associated with radiolarian cherts of Cretaceous age (Section 4: middle late Barremian-early early Aptian and Section 7: Valanginian to middle Aptian-early Albian), whereas the oldest N-MORBs were found in a section of Late Jurassic age (Section 5: early-early late Tithonian). Other N-MORBs are associated with radiolarian cherts of Early Cretaceous age (Section 8: late Valanginian-early Barremian). P-MORBs type rocks were found only in a section of Middle Jurassic age (Section 2: early-middle Bajocian to late Bathonian-early Callovian age). In this work, we document the occurrence of Late Triassic OIB-type rocks and of rocks showing different geochemical affinities (N-, E-, P-MORBs and OIB) generated within the same time span (Middle-Late Jurassic - Early Cretaceous). N-MORBs are compatible with composition of melts generated by partial melting of a depleted MORB mantle source. In contrast, OIBs are compatible with partial melting of an enriched-type mantle source. E-MORBs may have derived from mantle source slightly enriched with respect to a DMM source, whereas P-MORBs are compatible with melts generated from a mantle source significantly enriched, compared to DMM.

NEOGENE RADIOLARIAN BIOSTRATIGRAPHY FROM ODP LEG 119, SITE 745

Abundant, generally well preserved radiolarians were used in a stratigraphic analysis of the Neogene sequence of ODP Leg 119, Site 745. Detailed biostratigraphic analysis has been undertaken of radiolarian assemblages of the Pliocene-Pleistocene sequence. Seventy-seven radiolarian taxa were identified including three reworked forms. Twenty-one stratigraphically important species are described and illustrated from this 99.55 m long core, and allow the recognition of four radiolarian zones, i.e., Phi, Chi, Psi and Omega (from oldest to youngest) and the Plio-Pleistocene boundary. These are then correlated with the earlier established zones and boundary in the Southern Ocean.

Registro Faunístico y Paleoambientes del Cuaternario Tardío, Provincia de la Pampa, Argentina

Fil: Montalvo, Claudia Ines. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina

Ammonite-benthic Foraminifera turnovers across the Lower-Middle Jurassic transition in the Lusitanian Basin (Portugal)

This paper describes and characterises the co-occurrence of ammonite and benthic foraminiferal assemblages across the São Gião outcrop (Central Portugal), a reference section for the Lower-Middle Jurassic boundary in the Lusitanian Basin. The upper Toarcian-lower Aalenian marls and marly-limestones in this section provide a precise and detailed ammonite-based biostratigraphic zonation, with a mixed assemblage of northwest European and Mediterranean faunal elements, associated with benthic foraminifera assemblages with northern hemisphere affinities, both correlatable with the Aalenian GSSP at the Fuentelsaz section (Iberian Cordillera, Spain). A total of 447 well-preserved ammonite specimens and 13.116 foraminifera have been studied; no evidence was detected of any taphonomic processes that could have changed the original assemblages. From a biostratigraphic point of view, the ammonite record has enabled four biostratigraphic units to be recognised (the Mactra and Aalensis subzones of the Aalensis Biozone in the upper Toarcian, and the Opalinum and Comptum subzones of the Opalinum Biozone in the lower Aalenian). With regard to the benthic foraminifera, the taxa identified have enabled the Astacolus dorbignyi Zone and 11 bioevents to be identified, most of which representing local biostratigraphic proxies. However, the increase in the relative abundance of Lenticulina exgaleata Dieni from the upper part of the Opalinum Subzone to the lower part of the Comptum Subzone has a regional value. The constant and continuous ammonite record of northwest European taxa, together with typical Mediterranean taxa – namely Grammoceratinae – throughout the section, the high relative abundance of Miliolina representatives – generally interpreted as foraminifers typical of shallow waters – and the absence of foraminiferal forms typical of cool waters, do not support the inference of cool seawater temperatures attributed to the Early Aalenian, or the global character of the “Comptum cooling event”, at least with reference to the Lusitanian Basin.

A review of past and recent research on Cretaceous silicoflagellates

Previous knowledge of Cretaceous silicoflagellates has come primarily from scattered Maastrichtian or late Campanian localities. Silicoflagellates from the earlier Upper Cretaceous have been observed from the southern shore of the Baltic Sea and eastern slope of the northern Ural Mountains, and Lower Cretaceous from the Weddell Sea near Antarctica are also known. Much of the previous work, including type specimens for genera and species, have been illustrated with few and simple line drawings. Taxonomic distinctions and evolutionary lineages have often been speculative. Recent studies of Santonian and lower Campanian marine sediments from several sites in the northern Canada Arctic Margin and Archipelago substantially increase our knowledge of Cretaceous silicoflagellate morphology, biostratigraphy, and early evolutionary history. This work, which develops from previous diatom studies, provides new information on the enigmatic genera Cornua and Variramus, describes new genera and species, and presents new information on the timing of silicoflagellate evolutionary events. Seven new biostratigraphic zones replace the previously applied single biostratigraphic unit for the Cretaceous. This article reviews recent silicoflagellate discoveries in the context of previous work to provide a current general knowledge of the subject that includes important taxa.

Biostratigraphy and biochronology of the Monte Hermoso Formation (early Pliocene) at its type locality, Buenos Aires Province, Argentina

The Monte Hermoso Formation, cropping out at its type locality of Farola Monte Hermoso (Buenos Aires Province), is a classical fossiliferous unit of the South American Neogene, highlighted by the abundance and diversity of its vertebrate remains. However, its biostratigraphy and age have been largely debated, and numerous discrepancies and controversies have been stated. In this regard, the result of the analysis of new materials recovered from the different levels of this formation, following a strict control of stratigraphic provenance, is here reported. As well, the provenance of specimens of previous collections has been evaluated. The studied assemblage consists of Osteichthyes, Amphibia, Reptilia, Aves and Mammalia. These latter are the most numerous and belong to the Didelphimorphia, Polydolopimorphia, Rodentia, Notoungulata, Litopterna and Xenarthra. The recorded taxa suggest no important faunistic variations among the different levels of the Monte Hermoso Formation that would imply significant chronological differences, and hence, justify the recognition of two biostratigraphic units. The analysis of the first and last records as well as the taxa considered as exclusive, does not support the validity of the biozones of Trigodon gaudryi and Neocavia depressidens previously proposed. On this basis, a new scheme for the Monte Hermoso Formation at its type locality is proposed, including a new single biostratigraphic unit. This unit is the Eumysops laeviplicatus Range Zone, which represents the biostratigraphic base for the Montehermosan Stage/Age of the early Pliocene.

The Late Cambrian (Furongian) trilobiteTangshanaspisZhou and Zhang, 1978, in North America

Tangshanaspis Zhou and Zhang, 1978 (Family Missisquoiidae), has been reported widely from western North America and has been assigned invariably to a single species, T. depressa (Stitt, 1971b). The base of the T. depressa Subzone as defined in Oklahoma is an important biostratigraphic datum for inter-regional correlation of uppermost Cambrian strata. Study of previously undescribed material in collections from Oklahoma shows that T. depressa is, in fact, a composite of cranidia and pygidia that belong to two stratigraphically segregated species in the Signal Mountain Formation. Tangshanaspis silveri n. sp. includes the pygidial morph originally attributed to T. depressa. Revision of the species from Oklahoma allows definition of a new biostratigraphic unit, the Tangshanaspis Zone, which is divided into a lower T. silveri Fauna and an overlying T. depressa Fauna; in addition to the eponymous species, the T. depressa Fauna includes pygidia that represent two additional species of Tangshanaspis that are placed in open nomenclature. Correlation with other areas suggests that the “Missisquoia” mackenziensis Fauna of northern Canada may be equivalent to the T. silveri Fauna of Oklahoma, rather than a pre-Tangshanaspis interval that is unrepresented elsewhere in Laurentian North America.

BIOSTRATIGRAPHY AND REGIONAL ASPECTS OF THE TARBUR FORMATION (MAASTRICHTIAN) IN CENTRAL ZAGROS, SOUTHWEST IRAN

The aim of this study is to investigate the biostratigraphy and regional stratigraphy of the Maastrichtian deposits (Tarbur Formation) in the high outreaches of the Zagros Mountains in Chahar Mahal and Bakhtiyari Province, southwest Iran. The thickness of the investigated sequences is about 600 m in Tang-e-Vanak, 156 m inTang-e-Zendan,and 111 m in Kuh-e-Dozdaran sections. Shale and marls of the Gurpi Fm. (Campanian) mark the lower lithostratigraphic limit of the Tarbur Fm. in Kuh-e-Dozdaran section, whereas its upper limit is disconformably distinguished by the dolomitic Jahrom Fm. (Eocene). The Tarbur Fm. in Tang-e-Vanak andTang-e-Zendansections overlies the clastic Amiran Fm. (Maastrichtian) and is truncated with a sharp disconformity by the white dolomites of Shahbazan Fm. (Eocene). Biostratigraphically, the Tarbur Fm. is characterized by a Loftusia-Omphalocyclus assemblage zone, indicating a Maastrichtian age. Within this biozone, three regional subbiozones are proposed. They are: the Loftusia arabica range subzone , the Loftusia persica interval subzone , and the Loftusia baykali interval subzone . Based on the foraminiferal content, the age of the Tarbur Fm. in Kuh-e-Dozdaran section is assigned to the lower-middle parts of the Maastrichtian. Likewise, the Tarbur Fm. in Tang-e-Vanak and theTang-e-Zendansections is Maastrichtian in age, possibly extending locally into the Paleocene. The identification of the biostratigraphic limits of the Tarbur Fm. in the studied areas assists the reconstruction of the sedimentary basin in the Late Cretaceous.

The stratigraphical position and the use of the term Eopleistocene in Serbian geological literature

When the Calabrian Stage was included in the Quaternary frame by the decision of the 18th IGC (1948), it implied changes in the stratigraphical scale subdivision. At the beginning of the 1970s after the addition of the Calabrian Stage to the Quaternary and the lowering of the Quaternary boundary, it became evident that in the new scheme a gap of nearly 1 My was created in the case of fluvial and fluvio-lacustrine formations. The time frame of the Pleistocene could not include the oldest Quaternary fluvial and fluvio-lacustrine formations because of the lowering the Quaternary boundary to nearly 1.8 Ma, as was done in marine (Calabrian Stage) and terrestrial formations (Villafranchian Stage). This was one of the main reasons why the term Eopleistocene was implemented into the Serbian Quaternary stratigraphical terminology in 1972 and it was used in a semi-official way until 2010. In 2009, with the official ratification of the ICS (IUGS) of the lowering of the Neogene/Quaternary, i.e. Pliocene/Pleistocene boundary to 2.58 Ma, the use of the Eopleistocene in the Serbian stratigraphical terminology lost its meaning.The use of the term Eopleistocene in the Serbian stratigraphical scheme cannot be accepted in the sense of modern stratigraphical principles, because the mixing of the discriminatory concepts of the Alpine morphostratigraphical model with regional (exUSSR) climatostratigraphic and/or biostratigraphical units was obvious. As a term, Eopleistocene also caused a number of unclear and undefined problems/misunderstandings with regard to relations: Eopleistocene–Pleistocene, Eopleistocene–Lower Pleistocene, Eopleistocene-Alpine morphostratigraphical stages. With the developments and changes in the Quaternary stratigraphy, the Serbian Eopleistocene should be interpreted and replaced with (upper part of) Lower Pleistocene, because the base of the Eopleistocene had been identified at nearly 1.8 Ma and the Lower/Middle Pleistocene (Brunhes-Matuyama) boundary does not correspond with the Eopleistocene–Neopleistocene boundary.

Biostratigraphic constraints for the paleogeographic and tectonic evolution of the Alpine Central-Western Mediterranean orogenic belt (Betic, Maghrebian and Apenninic chains)

Vincoli biostratigrafici per la ricostruzione dell’evoluzione paleogegrafica e tettonica delle catena alpine del Mediterraneo centro-occidentale (Catene Betica, Maghrebide e Appenninica).Nelle catene alpine del Mediterraneo centro-occidentale, i sedimenti che testimoniano l’evoluzione ad avanfossa, e pre-datano l’inizio della tettonica compressiva, nei bacini dei domini continentali interni risultano di eta Oligocene superiore-Aquitaniana, mentre quelli dei domini oceanici del Bacino dei Flysch Maghrebidi e dell’Oceano Lucano si depositano fino al Burdigaliano superiore. L’eta della base dei piu antichi depositi di up-thrust, discordanti sulle unita dei Domini Interni, e burdigaliana, mentre un’eta langhiana e stata documentata alla base delle successioni discordanti sulle unita del Bacino dei Flysch-Oceano Lucano. L’eta dell’inizio della deformazione compressiva, pertanto, e ben accertata sia nei Domini Interni (Aquitaniano superiore-Burdigaliano inferiore) sia nel Dominio del Bacino dei Flysch-Oceano Lucano (Burdigaliano superiore-Langhiano inferiore). La chiusura dei domini oceanici e la collisione continentale tra la Microplacca Mesomediterranea e le placche principali del Mediterraneo centro-occidentale hanno avuto luogo tra il Burdigaliano terminale e il Langhiano medio. Ad esse si e accompagnato un generale back-thrusting di terreni delle Unita del Bacino dei Flysch al di sopra delle Unita Interne. Dall’esame di tutti i dati biostratigrafici disponibili non risultano evidenze di significativi diacronismi nell’evoluzione tettonica che ha portato all’individuazione dello stadio di avanfossa e alla costruzione di paleo-catene nell’intervallo di tempo che va dall’Oligocene terminale al Miocene medio. Infine, recenti dati biostratigrafici e petrografici su alcune unita appenniniche, come le Unita Sub-liguri e Toscane e l’Unita Lungro-Verbicaro in Calabria settentrionale, mettono in discussione le ricostruzioni paleogeografiche e l’evoluzione tettonica piu comunemente accettate dei Domini Appenninici.

AN UPPER VISÉAN (ASBIAN-BRIGANTIAN) AND SERPUKHOVIAN CORAL SUCCESSION AT DJEBEL OUARKZIZ (NORTHERN TINDOUF BASIN, SOUTHERN MOROCCO)

The Djebel Ouarkziz Formation, located in the northern part of the Tindouf Basin, in western Algeria and southern Morocco, is composed mainly of shales with interbedded limestones, dolostones and sandstones. The limestone beds are relatively thin, but are laterally persistent, and can be followed along strike for tens of kilometres. We have identified 19 limestone beds in three main sections; one logged along the road from Assa to Zag, a second in the Tinguiz-Remz Valley, 15 km to the east, and a third section 10 km west of the Assa-Zag road section. Rugose coral assemblages are recorded in most limestone beds, but the stratigraphically higher beds become more diverse However, many rugose genera and species are persistent throughout much of the succession. The oldest coral assemblages are Asbian in age and the youngest coral assemblages indicate a Serpukhovian age, as confirmed by foraminiferal biostratigraphy. The first appearance of rugose corals shows a different pattern than that in northern Moroccan basins; some common genera that first appear in the Asbian and lower Brigantian in northern Morocco and Europe, appear much later, in the upper Brigantian or Serpukhovian in the Djebel Ouarkziz. The genus Kizilia , which is rare in the Upper Visean in northern Moroccan basins, is, however, abundant in the Tindouf Basin. Interestingly, the occurrence of the genus Lonsdaleia in the Serpukhovian from Djebel Ouarkziz poses a palaeogeographic problem because of its absence in northern Moroccan basins (except as transported elements in Serpukhovian conglomerates). Similarly, Actinocyathus in the Serpukhovian in the Tindouf Basin is not present north of the Anti-Atlas Mountains. A possible coral migration route to the Tindouf Basin may be from the northeast via the Bechar Basin in Algeria, similar to that already inferred for foraminifers and calcareous algae.

PALAEOCLIMATIC CHANGES DURING LATE QUATERNARY IN NINGBO PLAIN

Base on the geological data acquired during the project on land and resource investigation,we defined the composition and distribution pattern of the Late Quaternary deposits in the Ningbo plain and constructed the sequence of the deposits.The paleoenvironment was studied by means of 14C dating,thermoluminescence dating and micropalaeontological studies.Both the lithostratigraphic and biostratigraphic units were established.Our results suggest that the Ningbo plain has suffered drastic climatic changes from the hot-moist,cool-arid,warm-arid,cold-moist,warm,cold-arid,hot-moist to the warm during Late Quaternary,with two times of large scale transgressions in Late Pleistocene and Holocene respectively.The palaeoclimatic change in the study area accorded well with the global change in the last 130 thousand years.

Relationship of Biometrical Aspect of Turritellidae with Geochronological Aspect in West Java

Mollusk paleontology research in Indonesia so far has not been widely utilized in various kinds of applications, especially in the geology. Although mollusk in Java is very rich, the study of correlation between mollusk appearances with geological condition is rare. This study aimed to determine Turritellidae base on morphological observations (qualitative) and quantitative (biometric method). The ultimate goal is to find out the relationship between of biometrical aspect of Turritellidae with geological development especially of chronological conditions. Stratigraphic analysis and sampling have done at five location of field survey. Site selection was based on the type locality of mollusk biostratigraphic unit arrange by Martin (1919) [1] and Oostingh (1938) [2]. The scattered analysis shows two large distribution of consistent groups based on shell size and geochronological aspect. Biometrical aspect of Turritellidae is reflection of the chronological aspect in West Java. Small size was appearance in Upper Miocene to Lower Pliocene and large shell in Pliocene to Pleistocene.

CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY OF THE S’ADDE LIMESTONE (MT. ALBO, OROSEI GULF): INSIGHTS INTO THE MIDDLE-LATE JURASSIC EASTERN SARDINIA PASSIVE MARGIN EVOLUTION

Calcareous nannofossil biostratigraphy has been performed on tree sections cropping out in Eastern Sardinia (Orosei Gulf, Mt. Albo). Calcareous nannofossils are rare to few and poorly to moderately preserved. Nevertheless thirteen bioevents have been recognized (S’Adde valley section) and a Late Bathonian-Early Tithonian age is derived for the S’Adde Limestone (Lms.). The inferred age constraints, integrated with data from the literature, allow the revision of the S’Adde Lms. chronostratigraphy, and the formalization of the S’Adde Limestone (Dieni & Massari 1985) as a lithostratigraphic unit. Qualitative evaluations of carbonate production/sedimentation rates for the north Mt. Albo area are proposed: the Late Bathonian-Callovian and Oxfordian were times of pronounced reduction of carbonate production/exportation, in agreement with the European passive margin evolution, also affected by starvation fenomena and condensations. A Middle-Late Jurassic basin-and-swell setting related to regional tensional tectonic activity is reconstructed for the north Mt. Albo area. The comparison of new and literature data allows framing the local and Eastern Sardinia passive margin evolution in the broader geodynamic and paleogeographic context of the southern European margin.

BIOSTRATIGRAPHIA OF THE PALEOGENE–NEOGENE DEPOSITS OF THE ALMA DEPRESSION IN CRIMEA.

Paleontological study of the Paleogene–Neogene deposits cored by boreholes 302 (Ravnopolie village) and 303 (Verhnesadovoe village) is provided – the Alma depression, the Crimea. Biostratigraphic units (zones and beds with fossils) are identified in the Paleogene section: beds with Subbotina turkmenica in marls and clays strata of the Kumian regiostage; foraminiferal zones Globigerapsis tropicalis s.l. and Planulina costata, nanoplankton zone NP19-20 in the Alma suite of the Almian regiostage; beds with Globigerina officinalis, beds with Lenticulina herrmanni, zones NP19-20, NP21 and NP22 in the Kyzyldjar strata and beds with Spiroplectammina oligocenica, zonа NP22 in the Zubakian strata of the Planorbellian regiostage. Neogene deposits lies with ravinement on the Lower Oligocene ones. In the neogene section the Novomoskovsk and the Dnepropetrovsk-Vassilievka beds of the Middle Sarmatian, the Maeotian and the Pontian are identified by characteristic associations of foraminifers, ostracodes and nanoplancton. Several levels of redeposition are established: Chokrakian mollusks, Konkian ostracodes and Paleogene foraminifers found out together in the Middle Sarmatian’s Dnepropetrovsk-Vassilievka beds. Thirty tree Middle Sarmatian gastropod species revealed in the Alma depression deposits for the first time. Also the representatives of genera Blinia, Flexitectura, “Amnicola”, Odostomia, Omalogyra and Melanochlamys are identified in the territory for the first time.

Aptian (lower Cretaceous) ammonite biostratigraphy of the Francisco Zarco Dam stratigraphic section (Durango State, northeast Mexico)

This work deals with the study of the ammonoid record of a classical stratigraphic section of Aptian age, the Francisco Zarco Dam (Durango State, northeast Mexico). A detailed biostratigraphical analysis considered 1281 specimens systematically sampled on a bed-by-bed basis. Taphonomy, taxonomic composition and paleocology of the studied assemblage, were also stressed. We formally propose an ammonite zonation for this section, which consists of two interval zones, Dufrenoyia justinae and Gargasiceras? adkinsi, one taxon range zone Caseyella aguilerae, and one biohorizon Huastecoceras trispinosoides. Among those biostratigraphic units, three are of new definition. Another topic discussed herein concerns to the problematic definition of the Lower-Upper Aptian boundary using the first stratigraphical appearance of the genus Epicheloniceras. From a paleoecological point of view, we recognized the ammonoid assemblage of the Francisco Zarco Dam section, to be representative of a distal platform environment. Finally, we compared the zonation built for this section with that considered the standard zonation for the Tethyan Domain, concluding that the differences are so substantial that an independent zonation for the Central Atlantic is necessary.