Gansserina Gansseri Zone Research Articles

Biostratigraphy of Shiranish Formation from Selected Wells, Central of Iraq

The Quantitative high-resolution planktonic foraminiferal analysis of the subsurface section in three selected wells in the Ajeel Oil Field (Aj-8, Aj-12, and Aj-15) in Tikrit Governorate, Central Iraq has revealed that Shiranish Formation deposited in Late Campanian- Latest Maastrichtian age. This formation consists mainly of marly and marly limestone yielding diverse planktonic foraminiferal assemblages and calcareous benthic foraminifera, with a total of 46 species that belong to 23 genera, Three zones and four subzones, which cover the Late Campanian to the Latest Maastrichtian, were identified based on the recorded planktonic foraminifera and their ranges. They are as follows:1. Globotruncana aegyptiaca Zone that dated to be Late Campanian 2. Gansserina gansseri Zone that refers to Early Maastrichtian 3. Abathomphalus mayaroensis Zone that indicates Late Maastrichtian, in this section, the Abathomphalus mayaroensis Zone is divided into four subzones, namely in that order from bottom to top: Racemiguembelina fructicosa (Early Late Maastrichtian), Pseudoguembelina hariaensis (Middle-Late Maastrichtian), P. palpebra ( Late Late Maastrichtian), and Plummerita hantkeninoides (latest Maastrichtian).

ХАРАКТЕРИСТИКА ВІДСЛОНЕНИХ РОЗРІЗІВ ТУРОНУ-МААСТРИХТУ ПЕНІНСЬКОЇ ЗОНИ УКРАЇНСЬКИХ КАРПАТ ЗА ДРІБНИМИ ФОРАМІНІФЕРАМИ

Purpose. Micropaleontological characteristics of individual exposed sections of Turonian-Maastrichtian sediments of the Pieniny Klippen Belt in the Ukrainian Carpathians with detailed age determination by foraminifera. Method. Field geological and stratigraphic research, foraminiferal analysis. Results. In the studied sections, Turonian, Coniacian, Campanian and Maastrichtian deposits were identified. The deposits of the Lower Turonian are determined by the disappearance of the genus Rotalipora and the appearance of the species Dicarinella hagni; the Upper Turonian was identified by the distribution of representatives of the genus Marginotruncana. According to the division of the Upper Cretaceous of the Ukrainian Carpathians after planktonic foraminifera, the Dicarinella concavata Zone (top of the Turonian-most of the Coniacian) and the sequence of zones in the Campanian-lower Maastrichtian interval were identified: Globotruncanita elevate Zone; Contusotruncana morozovae Zone, Globotruncanita stuarti Zone. The established subdivisions are correlated with the biochronozones of the modern Geologic Time Scale such as Dicarinella concavata Zone (top of the Turonian – most of the Coniacian), Globotruncanita elevate Zone, Contusotruncana plummerae Zone, Radotruncana calcarata Zone, Globotruncanella havanensis Zone, Gansserina gansseri Zone within the Campanian-lowermost Maastrichtian. Scientific novelty. For the first time, exposed sections of the Turonian-Maastrichtian of the Pieniny Klippen Belt of the Ukrainian Carpathians were studied and correlated with modern regional and international foraminiferal scales for the appearance of index species. Practical significance. The results obtained are important for the compilation of regional stratigraphic schemes and interregional correlation of sediments.

Planktonic foraminiferal distribution of the Late Cretaceous to late Paleocene deposits of the Bandar Abbas area (Zagros Belt, SW Iran): An update of the bio- and lithostratigraphic framework

In this paper, we present a biostratigraphic study of the planktonic foraminiferal associations of the Gurpi Formation outcropping in the Bandar Abbas area of the Zagros Belt (SW Iran). Two stratigraphic sections, Kuh-e Khush and Kuh-e Khamir, were logged and sampled, and the identification of the planktonic foraminiferal assemblages has allowed the recognition of eight Cretaceous biozones, namely Dicarinella asymetrica Zone, Globotruncanita elevata-Globotruncana ventricosa Zone, Radotruncana calcarata Zone, Globotruncanella havanensis Zone, Radotruncana calcarata–Globotruncana aegyptiaca Zone, Globotruncana aegyptiaca-Gansserina gansseri Zone, Gansserina gansseri Zone and Contusotruncana contusa-Abathomphalus mayaroensis Zone. This planktonic foraminiferal zonal framework reveals a latest Coniacian to late Maastrichtian age for the deposits of the Gurpi Formation in the two studied sections. The Cenozoic Interval of the studied sections, represented by the Pabdeh Formation, is attributed to the P3–P6a integrated Zone in the Khush section and the P4c Subzone (Acarinina soldadoensis) in the Khamir section. The data show that the Gurpi Formation at the Khamir locality rests disconformably upon the shallow neritic facies of the Ilam Formation, while in the Khush section this formation disconformably overlies the shallow carbonates of the Sarvak Formation. In addition to the in situ biota, reworked microfossils, such as calpionellids, calcareous algae and benthic foraminifera from older Jurassic (Surmeh Formation) and Cretaceous formations (Surgah equivalent, Sarvak, Kazhdumi and Dariyan formations) are recorded within several stratigraphic levels of the Gurpi Formation.

Biostratigraphy of planktonic foraminifera in the Abtalkh Formation and determination of the Santonian/Campanian Boundary in the Kopeh-Dagh Sedimentary Basin

ABSTRACT:We studied the Abtalkh Formation from five outcrops (Sheikh, Hajgelichkhan, Qarehso, Muzduran, and Deraz-Ab) in the Kopeh-Dagh sedimentary basin. A total of 30 species of planktonic foraminifera belonging to 21 genera were recorded. These species were used to subdivide the Abtalkh Formation into seven biozones (Dicarinella asymetrica Zone, Globotruncanita elevata Zone, Contusotruncana plummerae Zone, Radotruncana calcarata Zone, Globotruncanella havanensis Zone, Globotruncana aegyptiaca Zone, and Gansserina gansseri Zone). The Abtalkh Formation was deposited during the late Santonian-latest Campanian and the Santonian-Campanian boundary is identified based on the last occurrence of Dicarinella asymetrica. The base of the Campanian stage was delineated by the extinction of the marginotruncanid group, the first occurrences of Pseudotextularia nuttalli and Rugoglobigerina rugosa, and on the last occurrence of Dicarinella asymetrica.

Earliest Campanian - latest Maastrichtian sequence stratigraphy based on planktonic foraminifera, Fars province, Zagros, Iran

The Gurpi, Tarbur and Sachun formations have been investigated in the studied section in the Fars Province, in order to determine their sequence stratigraphy. On the basis of done studies on the cores of borehole, four main microfacies have been recognized in four stratigraphic sequence deposited during the Campanian to Maastrichtian. The lowermost sequence, was deposited in the early Campanian-early late Campanian which include wackestone to packestone texture with Globotruncanita elevata Zoneand Globotruncana ventricosa Zonethatrepresentative of the deep marine and outer ramp. The intermediate and uppermost sequences (sequences two, three and four) display well developed deposits formed in the end of the Campanian (Radotruncana calcarata Zoneand Globotruncanella havanensis Zone), formed during the Maastrichtian (Globotruncana aegyptiaca Zoneand Gansserina gansseri Zone) and the end of the Maastrichtian (Omphalocyclus macroporus - loftusia sp assemblage Zone) on pelagic, hemipelagic, outer and middle ramp. On the basis of the sequence stratigraphic chart, the transgression of the upper Cretaceous sea started since the early Campanian and continued gradually until the early Maastrichtian. Then, until the end of Maastrichtian, the area has been emerged. The sequence stratigraphic architecture of Campanian/ Maastrichtian Gurpi, Tarbur and Sachun formations model is in a good agreement with global sea level changes.

Timing of depositional regime changes during the Late Cretaceous evolution of the Southern Pontides (Ankara, Central Anatolia, Turkey)

During the Cretaceous, vast amounts of marine sediments were deposited along the south-facing active margin of the Eurasia. A stratigraphic section of 91 m was analyzed for planktonic foraminifera (75 samples), with the aim of establishing a refined biostratigraphy of Cenomanian–Campanian deposits in Central Anatolia. A biostratigraphic framework comprising nine biozones was established. In ascending order, the Rotalipora cushmani, Whiteinella archaeocretacea and Helvetoglobotruncana helvetica zones were defined in the uppermost Cenomanian–Turonian interval. The lack of Coniacian index markers suggests the existence of a hiatus for this interval. In the upper part of the section, the Dicarinella asymetrica, Globotruncanita elevata, Contusotruncana plummerae, Globotruncanella havanensis and Globotruncana aegyptiaca zones were identified for the Santonian and Campanian deposits. The presence of Gansserina gansseri, Globotruncanita angulata, G. conica and G. pettersi in the uppermost part of the section shows that the section ends at the base of the Gansserina gansseri Zone, indicating uppermost Campanian. The planktonic foraminifera biozonation framework provides strong evidence for the timing of the depositional history of the active continental margin that developed south of the Pontides. These phases are mainly the formation of olistostromes of pre-Santonian age, following condensed carbonate deposition during the Santonian and finally the switch from forearc deposition to the formation of a thick sequence of siliciclastic succession starting in the Campanian.

Foraminiferal biostratigraphy and paleobathymetry of the Maastrichtian – Paleocene succession at the north Farafra Oasis, Western Desert, Egypt

The Upper Cretaceous–Paleogene successions are well exposed at the Farafra Oasis, Western Desert, Egypt. The studied succession is distinguished into three formations arranged from base to top: Khoman (Maastrichtian), Dakhla and Tarawan (Paleocene). The identification of foraminiferal association yielded 55 species (28 planktonic and 27 benthonic). Most of them are considered as important biostratigraphical markers, especially in the Tethyan Realm. Based on planktonic foraminifera, nine biozones are differentiated, the Globotruncana aegyptiaca Zone, Gansserina gansseri Zone, Contusotruncana contusa Zone, Parasubbotina pseudobulloides Zone, Subbotina triloculinoides Zone, Praemurica uncinata Zone, Morozovella angulata-Igorina albeari Zone, Igorina albeari - Globanomalina pseudomenardii Zone and Globanomalina pseudomenardii- Acarinina subsphaerica Zone. The Cretaceous/Paleogene boundary (K/P) lies at the boundary between the Khoman and Dakhla formations. The biostratigraphic framework points to the absence of the Abathomphalus mayaroensis Zone of Late Masstrichtian and Guembelitria cretacea (P0) and Parvularugoglobigerina eugubina (Pα) zones of Early Paleocene. Therefore, the K/P boundary starts with the sudden disappearance of all the Cretaceous genera such as Globotruncana, Globotruncanita, Hedbergella Archaeoglobigerina, Heterohelix, Gansserina and Contusotruncana, followed by the appearance of Danian species such as Parasubbotina pseudobulloides (Plummer), Subbotina triloculinoides (Plummer) and Praemurica uncinata (Bolli). An attempt to estimate the paleobathymetry is done based on the investigated foraminiferal assemblages.

The Late Cretaceous Fucoid Marl of the Ropianka Formation in the Kąkolówka Structure (Skole Nappe, Outer Carpathians, Poland) – lithology and foraminiferal biostratigraphy

A 250-m-thick sedimentary succession dominated by siliciclastic deposits occurs in the Kąkolowka Structure of the Skole Nappe. The succession was deposited in the inner part of the Skole Basin during the Late Cretaceous. In position and age, it corresponds to the Kropivnik Fucoid Marl of the Wiar Member (a subdivision of the Ropianka Formation), which was comprehensively described in the external part of the Skole Nappe. In this study, the authors provide the first complete data set on the lithological development and biostratigraphy of the Kropivnik Fucoid Marl from the inner part of the Skole Nappe. The results are compared to previous data from the outer part of the Skole Nappe. In the Kropivnik Fucoid Marl of the Kąkolowka Structure, three main heterolithic facies associations are distinguished: shale-sandstone, marl-sandstone and sandstone-shale. The occurrences of hard, platy and soft marls within siliciclastic rocks are typical of the sections studied. The features observed indicate a turbiditic origin of the deposits studied, including the hard, platy marls. The allogenic material of the strata described includes the small, fragile tests of planktonic foraminifera, which were redeposited from the outer parts of the Skole Basin. Particularly large concentrations of planktonic foraminifera were observed in the hard, platy marls. They are less common in the soft marls and shales. In the Zimny Dzial section, a diverse assemblage of benthic and planktonic foraminifera was found. The Kropivnik Fucoid Marl was dated as uppermost Campanian to lowermost Maastrichtian on the basis of planktonic foraminifera, which represent the Gansserina gansseri Zone. The agglutinated foraminiferal assemblages are representative for the lower part of the Rzehakina inclusa Zone and the co-occurrence of the Caudammina gigantean (Geroch) acme with Rzehakina inclusa (Grzybowski) was observed.

Biostratigraphy and Sequence Stratigraphy of Campanian and Maastrichtian Succession, Qutbabad Well, Zagros (Iran)

The Qutbabad section of the Gurpi, Tarbur and Sachun Formations in the Fars Province (Zagros Basin) has been studied, in order to determinate its microfacies and sequence stratigraphy. On the basis of thin section studies of cores from Qutbabad Well in the Gurpi, Tarbur and Sachun Formations of the Zagros Basin, four main microfacies have been recognized within four stratigraphic sequences deposited during the Campanian to Maastrichtian. Depth and sea level changes were the main controls on the distribution of these microfacies. The microfacies are: Pelagic; Hemi-Pelagic; Outer ramp; and Middle ramp. The lowermost sequence was deposited in the Early Campanian-early Late Campanian and includes wackestone to packestone textures with biozones Globotruncanita elevate and Globotruncana ventricosa representative of the Pelagic, Hemipelagic and Outer (ramp/shelf). The intermediate and uppermost sequences (sequence two, three and four) display well developed deposits formed at the end of the Campanian (Radotruncana calcarata zone and Globotruncanella havanensis zone), beginning of the Maastrichtian (Globotruncana aegyptiaca zone and Gansserina gansseri zone) and the end of the Maastrichtian (Omphalocyclus macroporus - loftusia sp assemblage zone) on the Pelagic, Hemipelagic, Outer and Middle ramp. On the basis of the sequence stratigraphic chart, the transgression of the Upper Cretaceous Sea started from the Early Campanian and continued gradually towards the Early Maastrichtian. Then, until the end of Maastrichtian, has had regression. This resulted that the sequence stratigraphic model of the Campanian- Maastrichtian Gurpi, Tarbur and Sachun Formations has architecture similar to those that have developed from global sea level changes.

The Campanian–Maastrichtian foraminiferal biostratigraphy of the basement sediments from the southern Pannonian Basin (Vojvodina, northern Serbia): implications for the continuation of the Eastern Vardar and Sava zones

Abstract Micropalaeontological and biostratigraphical studies included Campanian-Maastrichtian complexes from five oil exploration wells drilled in northern Serbia (Vojvodina): the first is a carbonate-clastic complex and second is a complex containing ophiolites intercalated with hemipelagic and pelagic sediments. Within the studied complexes, rich associations of planktonic and benthic foraminifera, calcareous nannoplankton, palynomorphs, as well as shallow and deep-water fossil detritus were determined. The presence of relatively rich associations of planktonic foraminifera allowed recognition of two biozones: the Globotruncana ventricosa Zone, observed in the sediments of the carbonate-clastic complex and the Gansserina gansseri Zone, observed in both complexes. Except biozones, based on documented index species, for some units in both complexes, larger benthic foraminifera species had special biostratigraphical value, and in some of them, the calcareous nannoplankton zones were recognized. The studied complexes represent deep-water formations, generated in oceanic island arc and trough zones. The presence of limestones, which originate from destroyed rudist reefs, is explained by transfer by means of gravitational transport mechanisms of shallow-water sediments to deep-water depositional environments. In this paper, the results of more detailed biostratigraphical and palaeo-ecological studies of foraminifera associations in Campanian-Maastrichtian complexes in Vojvodina are presented. Combined with lithological studies, seven units were determined within the complexes. The obtained results are important as a part of multidisciplinary, regional exploration of both complexes, generated in specific geological conditions, that today constitute a part of the pre-Neogene basement complex in the southeastern part of the Pannonian Basin. The Campanian- Maastrichtian carbonate-clastic complex represents sedimentary cover of the Eastern Vardar Ophiolitic Unit, while the ophiolites intercalated with hemipelagic and pelagic limestones belongs to the Sava Zone.

Biostratigraphy of the Gurpi Formation (Santonian–Maastrictian) by using Globotruncanidae, Zagros Mountains, Iran

The study of Globotruncanids of the Gurpi Formation at Sepidar anticline in Zagros Mountains led to distinguishing Santonian to Late Maastrichtian biozones. Eight biozones were determined: biozone I (Dicarinella asymmetrica Zone) belongs to Santonian. Biozone II (Globotruncanita elevata Zone), biozone III (Globotruncana ventricosa Zone), biozone IV (Radotruncana calcarata Zone), biozone V (Globotruncana stuarti Zone) and biozone VI (Globotruncanella havanensis Zone) are of the Early to Late Campanian. Biozone VII (Gansserina gansseri Zone) and VIII (Contusotruncana contusa Zone) suggest the latest Campanian to Late Maastrichtian.

Campanian–Maastrichtian foraminiferal stratigraphy and palaeoenvironment of the Lower Tar Member in the Wadi Tar section, Western Sirte Basin (Libya)

Upper Campanian–Maastrichtian sections on the western flank of the Hun Graben in the Western Sirte Basin (WSB) are displaying two major type facies based on the foraminiferal assemblages. The first one indicates open-marine to outer-shelf conditions, and is represented by numerous bathy-pelagic planktonic foraminiferal species referable to the Radotruncana calcarata, Globotruncana aegyptiaca and the lower part of the Gansserina gansseri Zone (all late Campanian).The second type facies indicates an inner-shelf environment and is represented in the middle-upper part of the Gansserina gansseri Zone (early Maastrichtian) and Racemiguembelina fructicosa (late Maastrichtian) dominated by epi-pelagic planktonic and large benthic foraminifers. Large benthic foraminiferal index species Siderolites calcitrapoides Lamarck and Omphalocyclus macroporus (Lamarck) occur in abundance by the middle–late Maastrichtian. Correlation between planktonic foraminiferal zonation and large benthic foraminiferal zonation is given. An open-marine to outer-shelf environment passed into shallower marine conditions during the late Campanian–early Maastrichtian to late Maastrichtian, then a slight deepening and again shallowing is noticed.

Planktonic foraminiferal biostratigraphy and quantitative analysis during the Campanian-Maastrichtian transition at the Oued Necham section (Kalâat Senan, central Tunisia)

The Oued Necham (ON) section (Kalâat Senan, central Tunisia) provides a well-exposed outcrop of a Campanian-Maastrichtian series that consists essentially of chalky limestones (i.e. the Abiod Formation) grading progressively to a marly unit (i.e. the El Haria Formation). The transitional Abiod-El Haria succession comprises a rich hemipelagic-pelagic fauna in the study area, but ammonites (e.g., Pachydiscus neubergicus, the Campanian/Maastrichtian (C/M) boundary index taxon) are scarce to absent, thus preventing the recognition of the standard zones defined for the Tethyan realm. However, the rich planktonic foraminiferal taxa of the El Haria Formation allow us to establish an accurate biostratigraphical scheme. Accordingly, this work presents a high-resolution planktonic foraminiferal biostratigraphy that is characterised by distinct bioevents associated with the reported C/M boundary (i.e. lowest occurrences (LOs) of Rugoglobigerina scotti and Contusotruncana contusa) at the Global Stratotype Section and Point (GSSP) of the Tercis-les-Bains section, south-western France. Based on these zonal markers, the rugoglobigerinids and multiserial heterohelicids are used to define a subzonal scheme spanning the standard Gansserina gansseri Zone, including the Rugoglobigerina rotundata Subzone indicative of the late Campanian and the Rugoglobigerina scotti Subzone and the Planoglobulina acervulinoides Subzone, respectively, indicative of the early Maastrichtian. The abundance of foraminiferal assemblages allowed us to carry out high-resolution quantitative analyses that document a significant climate cooling during the early Maastrichtian intermittent with short-term warming episodes. Thus, opportunist taxa (r strategists, mostly heterohelicids) thrived during the earliest Maastrichtian cooling event, whereas specialist taxa (k strategists, mostly double-keeled) that had dominated the late Campanian assemblages declined gradually without any extinction. Opportunist and specialist taxa fluctuated in opposite phases throughout the early Maastrichtian (LO of Rugoglobigerina scotti ? LO of Abathomphalus mayaroensis), suggesting essentially variations in water temperature. Since surface dwellers dominated the assemblages, they imply continuous sea surface optimal conditions of nutrient supply and water connectivity induced from upwelling currents.

Morphological Abnormalities and Dwarfism in Maastrichtian Foraminifera from the Cárdenas Formation, Valles–San Luis Potosí Platform, Mexico: evidence of paleoenvironmental stress

During the early Maastrichtian an assemblage rich in large foraminifera, mostly composed of orbitoidal foraminifera, developed in the shallow-water deposits of the Cardenas Formation (Valles–San Luis Potosi Platform, Mexico). Among them, the most abundant is Lepidorbitoides minima, some of which display a morphologically abnormal test consisting of polyvalent forms, conical tests and budding, which could be induced by abrupt changes in environmental factors. The occurrence of the abnormalities preceded the demise of this species and of all the larger foraminiferal association in the upper part of the Gansserina gansseri Zone (early Maastrichtian). The abnormalities could be induced by environmental stress, probably related to interplay of different events such as increased terrigenous input and the transition to deeper facies due to Laramide tectonic instability before the K/P boundary. A late Maastrichtian community of dwarfed planktic foraminifera composed of Trinitella scotti Bronnimann, Plummerita reicheli Bronnimann, Rugoglobigerina cf. macrocephala Bronnimann, Rugoglobigerina hexacamerata Bronnimann, Heterohelix punctulata (Cushman), Pseudoguembelina costulata (Cushman), Pseudotextularia intermedia de Klasz, Globigerinelloides asperus Bolli, Guembelitria cretacea Cushman, Rugoglobigerina rugosa (Plummer), Rugotruncana sp., Globotruncanita stuarti (de Lapparent), and Globotruncana arca (Cushman) developed in the upper part of the sequence. This uncommon morphology could also be related to the highly stressed paleoenvironmental conditions related to global climatic change and local tectonic activity. Associated with this planktic assemblage is a deeper-water dwarfed benthic foraminiferal community composed of Gyroidinoides nitidus (Reuss), Coryphostoma incrassata (Reuss), Pseudouvigerina plummerae Cushman, P. cretacea Cushman, Bolivina cretosa Cushman, Planulina texana Cushman and Cibicides harperi (Sandidge).

Upper Campanian-lower Maastrichtian planktonic foraminifers and biostratigraphy of the Moni Formation, southern Cyprus

The first data on the taxonomic composition and stratigraphic range of the late Campanian planktonic foraminifers encountered in the middle and upper parts of the Moni Formation, southern Cyprus, are reported. Finds of planktonic foraminifers are associated with the bentonitic clay that composes the matrix of the Moni Formation. The planktonic foraminiferal assemblages revealed are very similar to those from the Kannaviou Formation, western Cyprus, but they are more diverse and yield several key species missing in the Kannaviou sediments. The planktonic foraminiferal assemblages discussed are referred to the Globotruncana aegyptiaca Zone and to the lowermost Gansserina gansseri Zone of the upper upper Campanian of the standard scale. The intraregional correlation of the Moni sections, depth of erosion of the upper part of the formation, and its relationship with the Kannaviou Formation have been refined. When subdividing the upper Campanian sediments based on planktonic foraminifers it is suggested that additional datum planes are used, such as the FADs of Globotruncanella citae and Trinitella scotti. For tracing the Campanian-Maastrichtian boundary (GSSP), attention should be paid to the LADs of Globotruncana bulloides and Contusotruncana fornicata and the potential use of Globotruncanita (Elevatotruncana) eolita sp. nov. should be assessed. It is shown that subfamily Archaeoglobigerininae Salaj, 1987, emend. O. Korchagin is the older synonym of subfamily Archaeoglobigerininae Georgescu, 2005. Two poorly known and three new planktonic foraminiferal species are described.

Latest Maastrichtian foraminiferal assemblages from the Husów region (Skole Nappe, Outer Carpathians, Poland)

Latest Maastrichtian foraminiferal assemblages from the Husów region (Skole Nappe, Outer Carpathians, Poland) The Ropianka Formation (also known as the Inoceramian Beds) in the marginal part of the Skole Nappe (Husów region, the Gaj section) contains abundant, diverse and well preserved assemblages of Maastrichtian planktonic and benthic foraminiferids, assigned to the middle-upper part of the Gansserina gansseri Zone and to the Abathomphalus mayaroensis Zone. The composition of the assemblages indicates fluctuations of organic matter flux to the marginal part of the Skole Basin floor in the studied interval. The studied taxa are typical of the "transitional zone" between the Tethyan and the Boreal domains. The disappearance of planktonic foraminifers in the uppermost part of the section and appearance of some agglutinated taxa (Rzehakina fissistomata; abundant Conglophragmium irregularis and Glomospira charoides) points to a Paleocene age.

Biostratigraphic Study of the Gurpi Formation Based on Planktonic Foraminifera In Lar Area (Kuh-e-kurdeh Section)

AbstractThe study of planktonic foraminifera of the Gurpi formations at Lar area (Kuh-e-kurdeh section) enables me to find the most standard biozones defined in mediterranean regions, especially Tethysian domain. Five biozones were determined. Biozones I (Globotruncanita elevata zone) and II (Globotruncana ventricosa zone) and III (Radotruncana calcarata zone) indicate the Early Campanian and Middle and Late Campanian, respectively. Biozones IV (Globotruncanita stuarti zone) and V (Gansserina gansseri zone) suggest the Early and Middle Maastrichtian, respectively. In the Late Maastrichtian, due to decreasing in water depth at the study area, Abathomphalus mayaroensis zone defined in Tethysian domain was not recognised.

Latest Cretaceous foraminifera from the Cardenas Formation, San Luis Potosi, Mexico: Biostratigraphical, paleoenvironmental and paleobiogeographical significance

Foraminifera from the Cardenas Formation (San Luis Potosi) represent the upper part of the Gansserina gansseri Zone and are thus of early Maastrichtian age, revising the late Campanian or broadly Maastrichtian dates for these strata in the literature. The stratigraphical relationship of eight microfacies, based on lithology and faunal composition, suggests open marine sedimentation on a shallow platform, temporarily interrupted by a transient increase in terrigenous clastics indicating a regional tectonic event. The foraminiferal fauna was changed as a result, with planktic foraminifera becoming more abundant, and with significant replacements in the large benthic forams indicative of deeper water or stronger currents and eventually with the disappearance of the larger forams altogether. The sequence ends with major influx of poorly fossiliferous terrigenous clastics in the upper member of the formation. The assemblage of larger benthic foraminifera that inhabited the platform environment consisted of cosmopolitan species and others endemic to the Caribbean Province, whose range does not extend past the K/T boundary. In the region of this study, we show that the demise of this end-Cretaceous assemblage, together with associated rudists, came in the mid-Maastrichtian as the result of increased terrigenous clastic input and local subsidence associated with the development of the Sierra Madre Oriental fold belt to the west.

Morphometric analysis of the genus Omphalocyclus from the Late Cretaceous of Turkey: new data on its stratigraphic distribution in Mediterranean Tethys and description of two new taxa

Omphalocyclus is an orbitoidal taxon poorly known from the Late Cretaceous benthonic foraminiferal inventory of the Tethyan realm. Apart from its debatable diagnosis only in the late Maastrichtian of western Tethys, the genus has also been discovered in much older beds in association with Orbitoides and Lepidorbitoides having rather primitive developmental stages. The morphometric analysis of A-forms in successive assemblages, ranging in age from (late) Campanian to terminal Maastrichtian, enables the documentation of phylogenetic changes for the first time. The most conspicuous change is found to be the general increase in the size of the embryon, which on average doubles by the end of the Maastrichtian. This trend is followed by the increase in the number of epi-embryonic chamberlets, which is however, not as significant as the former parameter. Omphalocyclus in the stratigraphically lowermost populations has mainly three to four primary epi-embryonic and no accessory epi-embryonic chamberlets. With the introduction of radial stolons, which seems to have taken place in horizons referable to the Gansserina gansseri Zone, only several accessory epi-embryonic chamberlets arise from the tritoconch. Instead, epi-embryonic chamberlets become rather larger in size and they also cover a wider portion of the embryon along its thick outer wall. Considering the suitable change in embryon size, and also some other morphologic features in successive populations, two new species, O. anatoliensis sp. nov. and O. cideensis sp. nov. are erected in late Campanian and late Campanian-early Maastrichtian populations respectively. The most advanced specimens in the late Maastrichtian are attributed to the long-known species O. macroporus [Lamarck, J.B., 1816. Histoire naturelle des animaux sans vertèbres, vol. 2. Verdière, Paris, pp. 1–568]. Thus, a tentative subdivision scheme comprising three successive species, O. anatoliensis – O. cideensis – O. macroporus, is proposed.

MAASTRICHTIAN INOCERAMID BIVALVES FROM CENTRAL CHIAPAS, SOUTHEASTERN MÉXICO

In central Chiapas (southeastern México) the last occurrence of inoceramid bivalves was recorded in strata of the predominantly terrigenous Ocozocoautla Formation. The inoceramids are associated with foraminifers of the Gansserina gansseri Zone (Late Campanian to Early Maastrichtian). The described species are: Cataceramus? cf. barabini (Morton, 1834), Cataceramus? cf. subcircularis (Meek, 1876), Trochoceramus aff. costaecus (Khalafova, 1966), Trochoceramus nahorianensis (Kociubynskij, 1968), and Trochoceramus tricostatus n. sp. Based on the inoceramid and foraminifer species present, the assemblage is assigned to the Early Maastrichtian. This age is important because at this level most of the typical inoceramids globally disappeared. This is the first report of the genus Trochoceramus in México, which is a good index fossil for the Early Maastrichtian and has a cosmopolitan distribution.