Total Range Zone Research Articles

Upper Cretaceous planktonic foraminiferal biostratigraphy of the Zagros Basin (West Iran) with reference to sea-level changes

In this study, an Upper Cretaceous sedimentary sequence in the Anaran Anticline (located in the central Zagros) is investigated to assess planktonic foraminiferal biozonations and implications for sea level changes. The thickness of this sequence is about 215 m, characterized by shales and limestones with thin marly limestone intercalations. In total, 51 species and 22 genera of planktonic foraminifera in 12 biozones spanning the middle Campanian to late Danian ages were delineated in the studied sequence. Additionally, planktonic foraminiferal morphological models, species abundance percentages, and the planktonic/benthonic foraminiferal ratio (P/B) ratios were assessed to reconstruct changes in sea level. The statistical studies on the different genera and species and the P/B ratio from the base to the top of the sequence indicate sea level transgressions during the middle Campanian and Maastrichtian in the Contusotruncana plummerae Interval Zone, Radotruncana calcarata Total Range Zone, Globotruncanella havanensis Partial Range Zone, Globotruncana aegyptiaca Interval Zone, Contusotruncana contusa Interval Zone, and part of the Abathomphalus mayaroensis Interval Zone.Moreover, species belonging to the deep-water morphotype (G. arca, G. hilli, G. linneiana, and G. ventricosa) are mostly present. Furthermore, two intervals of this sequence are associated with falling sea levels: 1) at the Campanian/Maastrichtian boundary in the middle of the Gansserina gansseri biozone; 2) from the late Maastrichtian close to the Cretaceous/Paleogene boundary with marly lithology.

Planktonic Foraminifera Biostratigraphy of Shiranish Formation in Piramagroon Anticline, NE Iraq

67 planktonic foraminiferal species were identified from the Shiranish Formation. On the basis of the stratigraphic distribution of the planktonic foraminiferal assemblages recognited of six biozones within the Shiranish Formation representing an age ranging from Middle Campanian – Early Maastrichtian, these zones are from older at base: 6 -Planoglobulina acervulinoides Interval Zone. 5 - Contusotruncana contusa Total Range Zone. 4 -Gansserina gansseri Interval Zone. 3 - Globotruncana aegyptiaca Interval Biozone. 2 -Globotruncanella havanensis Interval Biozone. 1 -Globotruncana ventricosa Interval Biozone

The Maastrichtian‐Danian in the SW Zagros Fold‐Thrust Belt (S. Iran): An Integration of Planktonic Foraminiferal Biostratigraphy and Gamma‐Ray Spectrometry

AbstractIn this study, the Maastrichtian‐Danian boundary was measured and sampled in two stratigraphic sections, the north and south flanks of the Dehnow anticline in Coastal Fars, Southern Iran. This boundary was also investigated in the drilled exploratory well‐1 in the same region. The lithology of the Maastrichtian‐Danian deposits consists of glauconitic, phosphatic argillaceous limestones and marlstones. 30 genera and 77 species of planktonic foraminifera have been determined. The recognized biozones are the Gansserina gansseri Interval Zone, and the Contusotruncana contusa Interval Zone, which indicates latest Campanian to middle Maastrichtian age for the upper part of the Gurpi Formation. In addition, the Eoglobigerina edita (P1) Partial Range Zone, Praemurica uncinata (P2) Lowest Occurrence Zone, Morozovella angulata (P3) Lowest Occurrence Zone and Globanomalina psudomenardii (P4) Taxon Range Zone represent a Danian to Thanetian age for the lower part of the Pabdeh Formation. From the absence of the Abathomphalus mayaroensis Interval Zone, Pseudoguembelina hariaensis Interval Zone, Pseudotextularia elegans Interval Zone, Plummerita hantkeninoides Interval Zone, Guembelitria cretacea (P0) Partial Range Zone and Parvularugoglobigerina eugubina (Pα) Total Range Zone, it can be deduced that there is a paraconformity across the Maastrichtian–Danian boundary in the studied area, this hiatus encompassing the late Maastrichtian and the earliest Danian. Danian deposits from the study area contain reworked glauconitized macrofossils, planktonic and benthic foraminifera of the Cretaceous. The obtained surface gamma‐ray spectrometry logs resemble the exploratory well‐1 gamma‐ray wireline log.

Study of main planktonic foraminifera(Turonian-Santonian) in Kopeh-Dagh sedimentary environment, NE Iran

In order to study the fossil contents of the Abderaz Formation for biostratigraphical purposes the 500 meters thick section was sampled at type section. The sequence is mainly made up of grey shales and marls with two units of chalky limestone in upper part. The lower contact of the formation with Aitamir Formation is disconform while the upper contact with Abtalkh is continuous. Fifty six species belonging to 16 genera were identified and four biozones were differentiated. These are: Helvetoglobotruncana helvetica (Sigal)total range Zone, 2-Marginotruncana sigali - Dicarinella primitiva (Premoli Silva and Sliter)Partial range Zone, 3- Dicarinella concavata (Sigal)interval Zone and4-Dicarinella asymetrica (Postuma)total range Zone. Based on, these an age of Turonian-Late Santonian is quoted to the formation. Also it was shown that Helvetoglobotruncana helvetica, the index species for middle Turonian exists at the base of the formation while, in the samples immediately below this belonging to Aitamir Formation Rotalipora appenninica, the index for middel cenomanian was recorded. Therefore, lack of index species for late Cenomanian- early Turonian shows a gap spanning this period between the Aitamir and Abderaz formations. This could be a result of sub Hersinian orogeny.

HIGH RESOLUTION BIOSTRATIGRAPHIC ANALYSIS OF THE DANIAN STAGE, PER FAT SECTION, DUHOK AREA, KURDISTAN REGION, NORTH OF IRAQ

The occurrence of the Danian Stage at Kurdistan Region of Iraq, particularly in the high folded zone, was a debatable subject by many authors. Most of the previous studies believe that it is poorly preserved. This study reviews the Danian sequence at Per Fat of Duhok area using high resolution biostratigraphic analysis of the planktic foraminifera. The Danian stage sequence in the studied locality is represented by the marlstone, shale, and marly limestone rock types of the Aaliji Formation. Occasional iron oxides and microscopic glauconites intervals are characteristics. The thickness of the Danian sequence is about 29.71 m. The sequence is underlined by the Upper Cretaceous Shiranish Formation, and overlies by the green-olive clastic sediments of the Paleocene Kolosh Formation. Biostratigraphic zonation of the identified foraminiferal assemblages shows the occurrence of the four Danian Planktic foraminiferal biozones and three subzones including Guembelitria cretacea partial-range zone (P0); Parvularugoglobigerina eugubina total range zone (Pα); Parasubbotina pseudobulloides partial-range zone (P1); Globanomalina archaeocompressa partial-range subzone (P1a), Subbotina triloculinoides interval subzone (P1b), Globanomalina compressa-Praemurica inconstans interval subzone (P1c); and Praemurica uncinata interval zone (P2). This indicates a complete sequence of the Danian stage is preserved in the Per Fat section of Duhok area.

Depositional environment, sequence stratigraphy and biostratigraphy of the Gurpi formation in Fars zone, Zagros Basin (SW Iran)

To study the Gurpi Formation deposits in Fars area, 230 thin-sections which belong to Well No. 43 have been studied. The Gurpi Formation is 155 m in thickness. Lithology of the Gurpi Formation is mainly composed of thin to medium limestone, argillaceous limestone and shale. Lower boundary of the Gurpi Formation with the Ilam Formation is continuous and its upper boundary with the Pabdeh Formation is disconformity. In biostratigraphy analysis, 14 species belonging to 31 genera of planktonic and benthic foraminifers were identified, and 6 biozones were recognized based on planktonic foraminifera as follow: (1) Globotruncanita elevata Partial range Zone, (2) Globotruncana ventricosa Interval Zone, (3) Radotruncana calcarata Total range Zone, (4) Globotruncanella havanensis Partial range Zone, (5) Globotruncana aegyptiaca Interval range Zone, (6) Gansserina gansseri Interval range Zone. Based on the fossil contents and the identified biozones, the relative age of the Gurpi Formation is Early Campanian–Maastrichtian. Petrographic studies of the Gurpi Formation led to recognition of six facies including five carbonate facies and one shale facies. All facies of the Gurpi Formation belong to the open marine environment, which are deposited in a shelf model. Based on facies analysis and sea level curves, three depositional sequences along with four sequence boundaries due to discontinuities and relative levels of sea level falling were identified. The sequence boundaries at the lower boundary and in the middle part of the Gurpi Formation are type II sequence boundary (SB2). Only the upper boundary of depositional sequence 3 (the boundary between the Gurpi and Pabdeh formations) due to exposure and presence of erosion effects is revealed as a type I sequence boundary (SB1).

Biostratigraphy of Upper Cretaceous planktonic foraminifera of the Abtalkh Formation in an east-west transect, Kopet-Dagh Basin, northeastern Iran

The Upper Cretaceous Abtalkh Formation of the Kopet-Dagh Basin (northeastern Iran) was studied in four stratigraphic sections (Bahadorkhan, Hammam Galeh, Type section and Shorab). All sections display limestones, shales and calcareous shales. The Bahadorkhan section is approximately 480 m thick. We identified 32 planktonic foraminifera species belonging to 13 genera in 6 biozones: 1. Dicarinella asymetrica Total Range Zone, 2. Globotruncanita elevata Partial Range Zone, 3. Contusotruncana plummerae Interval Zone, 4. Radotruncana calcarata Total Range Zone, 5. Globotruncanella havanensis Partial Range Zone and Globotruncana aegyptiaca Interval Zone. Based on foraminiferal biostratigraphy, the Bahadorkhan section was dated to the latest Santonian to late Campanian. This study identifies 11 genera and 25 species of planktonic foraminifera in the 1500m thick Hammam Galeh section, spanning 7 biozones: 1. Dicarinella asymetrica Total Range Zone, 2. Globotruncanita elevata Partial Range Zone, 3. Contusotruncana plummerae Interval Zone, 4. Radotruncana calcarata Total Range Zone, 5. Globotruncanella havanensis Partial Range Zone, 6. Globotruncana aegyptiaca Interval Zone, 7. Gansserina gansseri Interval Zone. Latest Santonian to late Campanian ages have been established for the Abtalkh Formation. The type locality of the Abtalkh Formation is 750mthick and contains 31 planktonic foraminiferal species belonging to 12 genera. Based on this fossil content, we identified 6 biozones. The age of the formation is estimated to be the latest Santonian to late Campanian, as for the Bahadorkhan type section. The Shorab section of the Abtalkh Formation is 990m thick. In this section, 19 species belonging to 10 genera were identified, as were 5 biozones: 1. Globotruncanita elevata Partial Range Zone, 2. Contusotruncana plummerae Interval Zone, 3. Radotruncana calcarata Total Range Zone, 4. Globotruncanella havanensis Partial Range Zone, 5. Globotruncana aegyptiaca Interval Zone. Based on this fossil assemblage, the Shorab section dates to the early to late Campanian.

Small benthic foraminiferal biostratigraphy and palaeoecology during the Campanian-Maastrichtian transition in north-western Tunisia

Campanian-Maastrichtian (C-M) sediments in the Kalâat Senan area (north-western Tunisia) include rich microfauna. Small benthic foraminifera (SBF) analysis at the Wadi Necham (ON) section reveals significant biostratigraphic and palaeoecological changes during the C-M transition. A progressive evolutionary trend within the Bolivinoides lineage allowed us to establish the late Campanian B. decoratus Interval Range Zone (IRZ) and two successive zones in the early Maastrichtian, namely the B. miliaris IRZ and the B. draco Total Range Zone (TRZ), which span the standard planktonic foraminifera Gansserina gansseri IRZ. Foraminiferal semiquantitative data from the C-M transition interval at the studied section yield high values of planktonic/benthic (P/B) ratios (92%-98%) suggesting an upper to middle bathyal depositional palaeoenvironment. Assemblages of such a deep environment comprise diversified epibenthic and endobenthic taxa indicating major changes across and above the C-M transition. During the late Campanian (Bolivinoides decoratus Zone) endobenthic morphogroups dominate (71%) the assemblages as compared to epibenthic morphogroups, which reach 29%. In contrast, the abundance of epibenthic morphogroups increases to 40% just above the C/M boundary (Bolivinoides miliaris Zone) and suggests cooler and more oxygenated conditions on the sea floor. Epibenthic and endobenthic abundances fluctuate in opposite trends (40%-60%) throughout the early Maastrichtian (B. draco TRZ). These variations are interpreted to reflect mesotrophic conditions intermittently interrupted by eutrophic shifts associated with the early Maastrichtian cooling event. The relative proportion of endobenthics increased (60%-80%) again towards the late Maastrichtian (upper part of the B. draco TRZ), showing a particular increase in EnA morphogroups prevailing in the SBF assemblages. Moreover, test morphology analyses of SBF assemblages allowed us to distinguish six epibenthic (M1 to M6) and seven endobenthic (M7 to M13) morphogroups based on their mode of coiling. This classification reveals the flourishing of EpC M4 and M5 morphogroups during the early Maastrichtian due to more oxygenated conditions on the sea floor.

New latest Coniacian to middle Campanian foraminiferal data from the lower Zongshan Formation in the Chaqiela section, Gamba, southern Tibet

A first and detailed foraminiferal biostratigraphic work on the lower part of the Zongshan Formation (Limestone I and Calcareous Marl I sequence) in the Chaqiela section, Gamba, southern Tibet, allows the recognition of three latest Coniacian to middle Campanian planktic foraminiferal biozones: Dicarinella asymetrica Total Range Zone, Globotruncanita elevata Partial-Range Zone, and Contusotruncana plummerae Interval Zone. The base and top of the Santonian Stage in the Chaqiela section were placed at the lowest occurrence (LO) of Globotruncana linneiana and the highest occurrence (HO) of Dicarinella asymetrica, respectively. The deposition of the latest Coniacian to middle Campanian sediments of the lower Zongshan Formation in the Chaqiela section seems to have been continuous or at least without any major gap based on the planktic foraminiferal biozones and events.

Planktonic foraminiferal biostratigraphy and paleoenvironments at the Santonian-Campanian boundary of Northern Tunisia

The Santonian-Campanian boundary in Northern Tunisia has been studied in Oued el Khannga section, based on biostratigraphic and paleoecological analysis. The detailed biostratigraphic analysis allows us to define the stratigraphic distribution of diverse planktonic foraminifera and to establish a continuous biozonation. Sixty-six planktonic foraminiferal species belonging to 13 genera have been identified and two Tethyan planktonic foraminiferal zones have been organized, indicating the upper Santonian - lower Campanian age. These zones are: Dicarinella asymetrica (Total Range Zone) and Globotruncanita elevata/Globotruncana arca (Concurrent range zone). A major turn over event was recorded in this interval including the extinction of several species characterized by complex morphotypes with a double keel such as the genera of Dicarinella, Marginotruncana. In fact, the extinction of the index species D. asymetrica is the most important event which defines the Santonian-Campanian boundary. Many representative species of the genera Globotruncanita and Globotruncana occurred, for the first time, in the uppermost of the Santonian and thrived close to the Santonian-Campanian boundary. In addition some surviving species with a simple morphotype, which are considered like opportunistic taxa, crossed the boundary. This various responses of planktonic foraminifera and the fluctuation in diversity and in the number of species may be related to an increase in temperature and a deep outer shelf upper bathyal environment deposit.

Calcareous nannofossil and planktonic foraminiferal Biostratigraphy of Santonian to Danian in Göynük Basin, Bolu, Turkey

Biostratigraphy of Santonian-Danian calcareous nannofossils and planktonic foraminifera was studied in Göynük village and close surroundings located in northwest Turkey. Calcareous nannofossil and planktonic foraminifera assemblages from this time interval were investigated in detail in seven stratigraphic sections measured in the Değirmenözü Member, Yenipazar Formation and Seben Formation. The UC12 zone in the Santonian, UC13 zone, UC14a-bTP and UC15a-b-c-dTP subzones in the Campanian and UC20a-b-c-dTP subzones in the Maastrichtian were defined with nannofossil species assemblages.Planktonic foraminifera assemblages determined included Dicarinella asymetrica Total Range Zone (TRZ) from the Santonian, Globotruncanita elevata Partial-range Zone and Globotruncana ventricosa Partial-range Zone from the Campanian and Racemiguembelina fructicosa Partial-range Zone and Pseudoguembelina hariaensis Partial-range Zone from the Maastrichtian. There was a significant reduction in nannofossil species at the Cretaceous-Paleogene (K-Pg) boundary with dominance of Braarudosphaera bigelowii, Thoracosphaera sp. and Markalius inversus species and increased abundance of biserial planktonic foraminifera species. Just above this boundary in the Danian NP1 and NP2 nannofossil zones and Parvularugoglobigerina eugubina Taxon-range Zone, Parasubbotina pseudobulloides Partial-range Subzone (P1a), S. triloculinoides Lowest Occurrence Subzone (P1b), and G. compressa/Praemurica uncinata Lowest Occurrence Subzone (P1c) were identified from planktonic foraminifera.

Cenomanian-Turonian biostratigraphy of the Jardas Al Abid area, Al Jabal Al Akhdar, northeast Libya

The Upper Cenomanian-Turonian succession exposed at Jardas al’Abid area consists mainly of carbonates with siliciclastic intercalations. This succession is subdivided lithostratigraphically into: Qasr al’Abid (Late Cenomanian) and Al Baniyah (Late Cenomanian-Coniacian) formations. This sequence is relatively rich in macrofossil assemblages especially bivalves, gastropods, and echinoids with rare ammonites. Based on the first occurrence (FO) and last occurrence (LO) of some index species of these macrofossil groups, an integrated biostratigraphic framework has been constructed. The studied Cenomanian-Turonian sequence is subdivided biostratigraphically into three ammonite biozones; Pseudaspidoceras pseudonodosoides Total Range Zone, Choffaticeras segne Total Range Zone, and Coilopoceras requienianum Total Range Zone. Based on the rest of macrofossil assemblages other than the ammonites, eight biozones were recognized; Mecaster batnensis Total Range Zone, Ceratostreon flabellatum–Neithea dutrugei Acme Zone, Costagyra olisiponensis Acme Zone, Pycnodonte (Phygraea) vesicularis vesiculosa Acme Zone, Mytiloides labiatus Total Range Zone = Mecaster turonensis Acme Zone, Rachiosoma rectilineatum-Curvostrea rouvillei-Tylostoma (T.) globosum Assemblage Zone, Radiolites sp.-Apricardia? matheroni Total Range Zone, and Nerinea requieniana Total Range Zone. Most of the proposed biozones are recorded for the first time from Libya. The integration among these biozones as well as local and inter-regional correlation of the biozones have been discussed. The stage boundaries of the studied stratigraphic intervals are discussed, where the Cenomanian/Turonian boundary is delineated at the last occurrence (LO) of Pseudaspidoceras pseudonodosoides (Choffat), while the Turonian/Coniacian boundary is delineated arbitrary being agree with the LO of the Turonian fauna.

Investigation of Main Planktonic Foraminiferal Bio-Events in Surgah Formation at Pol-e-Dokhtar Area, South Western of Iran

Surgah Formation at Male-kuh well section with 82 meters thickness has been studied at Pol-e-Dokhtar area. Surgah Formation at mentioned section was composed of limestone and shaly limestone. The lower and upper contacts of studied formation with Sarvak and Ilam formations are conformed. Based planktonic foraminifera study 37 species belonging to 10 genera in frame of two planktonic foraminiferal biozones were identified respectively as below: 1) Dicarinella concavata Interval Zone; 2) Dicarinella asymetrica Total Range Zone. Finally, based on recent investigation have been detected middle Turonian-Late Santonian age for studied section. According to (Robaszynski and Caron 1979), the first occurrence of Dicarinella primitiva has been shown base of the Coniacian stage. The first occurrence of Di. primitiva was placed under the Turonian-Coniacian boundary. Robaszynski and Caron 1995 recorded the first occurrence of Dicarinella primitiva and Dicarinella concavata were simultaneous and assigned to late Turonian which correlated with ammonite’s species Subprionocyclus neptuni. In the correlation between ammonite and Dicarinella primitiva at Tethyan realm first occurrence of Di. primitiva was close to the Middle-Late Turonian sub stage. The base of Coniacian stage was identified based on the FODs of Archaeoglobigerina cretacea and Dicarinella concavata from planktonic foraminifera with FOD of Cremnoceramus walterdorfensis walterdorfensis from inoceramid group, while the base of Santonian stage recorded using LOD of Dicarinella primitiva, Whiteinellids group with FODs of Dicarinella asymetrica and Inoceramus aff. vistulensis (inoceramid species).

Palaeoenvironmental changes in the northwestern Tethys during the Late Campanian Radotruncana calcarata Zone: Implications from stable isotopes and geochemistry

This paper investigates the palaeoceanographic setting and evolution of two biostratigraphically well constrained Upper Cretaceous sections in the Eastern Alps of Austria. The duration of the investigated time interval is confined by the total range zone of Radotruncana calcarata which was a very short lived (806 000yrs) species as calibrated using orbital parameters. This results in a precise time frame for paleoenvironmental interpretations within this interval. Stable isotope stratigraphy links both sections to published records. The two studied sections are located at the passive (northern) margin of the European Foreland and at the active (southern) margin of a northwestern Tethys ocean branch, respectively. We use mineralogy, clay mineralogy, element geochemistry, carbonate-associated elements and element ratios, Sr isotope stratigraphy and stable C and O isotopes to characterize the profiles. Mn/Sr ratios as well as stable C and O isotopes indicate that the sediments are largely diagenetically unaltered. Both sections have a similar history concerning their sea-level evolution, i.e. a gradual third-order regression with short fourth-order transgressive intervals. The inferred water temperature increases at both locations and the overall primary production and nutrient availability increased slightly with time. Predominately suboxic conditions are confined to the southern profile and were interrupted by oxic spells of ~50kyr duration and even shorter periods of increases in primary production. We also found evidence of a strong aeolian influence on the cyclic deposition of marl–limestone couplets in the southern profile.The similar history at both geodynamic settings indicates that the southern block close to the subduction zone was relatively stable for the duration of R. calcarata total range zone.

Erratum to: Biostratigraphy and paleoecology of Upper Paleocene to Lower Oligocene deposits in Southeast of the Hajiabad Area (Zagros Basin, SW Iran)

This study deals with foraminiferal biostratigraphy and paleoecological interpretations for the Late Paleocene to the Early Oligocene carbonate sequence in the Zagros Basin, the Hajiabad Area, SW Iran. This sequence could be divided into three parts, basal fossil-less strata have related to Sachun Formation base on their stratigraphical position, the middle part involves dolomitic to dolomitic limestone of Jahrum Formation, and the upper part consists of the Lower Asmari Formation. In general, the bulk of the section consists of marine deposits, and it is possible to divide them in to several parts base on benthic foraminiferal biozones. The Late Paleocene to the Early Eocene (the Lower Jahrum Formation) has been distinguished by the Miscellanea, Kathina, Alveolina, Fallotella, Lokhartia, Orbitolites, and small rotalids Assemblage Zone. The Middle Eocene (the Middle Jahrum Formation) has been characterized by the Somalina Total Range Zone and the Nummulites-Alveolina Assemblage Zone. The Late Eocene (the Upper Jahrum Formation) has been distinguished by the Chapmanina, Pllatispira, Baccullogypsinoides Assemblage zone, and the outcrop of the Asmari Formation belongs to the Early Oligocene Base on the Nummulites vascus, Nummulites fichteli Assemblage Zone. Clustering content benthic foraminifera in the studied section base on their morphology, coiling, feeding habits, and habitats lead to identification of 15 distinct assemblages with similar ecological niches. Paleoecological reconstructions base on benthic foraminiferal communities indicate that five major ecological habitats include tidal flat and shore, restricted shelf, nonrestricted shelf, oligotrophic shelf, and open marine.

A Cenomanian-Turonian drowning unconformity on the eastern part of Kopet-Dagh basin, NE Iran

A Cenomanian-Turonian interval in the Mozduran pass section, eastern part of Kopet-Dagh basin (NE of Iran), was measured and studied in order to interpret the biostratigraphy and paleoecology (based on distribution of planktonic foraminifera). This section consists of 52.5-m light and gray marl and coincides with the Aitamir and Abderaz formation boundary. Based on study of 47 samples, 11 planktonic foraminifera genera and 27 species were encountered, and the following zones have been defined: Rotalipora cushmani Total Range Zone and three zones of Helvetoglobotruncana helvetica, Dicarinella primitiva-Marginotruncana sigali, and Dicarinella concavata as condenced zones. This study shows that the sediment record is incomplete in the section. This unconformity is just after a drowning succession, places in the Late Cenomanian-Early Turonian Whiteinella archaeocretacea Zone, and interpreted as a drowning unconformity. A paleoenvironmental model has been formulated to explain the successive paleocommunity changes during this drowning of the platform. We attribute the drowning of some parts of the platform to the occurrence of the Cenomanian-Turonian oceanic anoxic event. The impingement of anoxic waters over the platform could produce the drastic reduction of the carbonate producing observed in the stratigraphic section and therefore a reduction in carbonate accumulation rates. Subsidence and the Late Cenomanian-Early Turonian sea level rise were then able to drown the platform.

Biostratigraphy and Sequence Stratigraphy of the Gurpi Formation at Deh Dasht Area, Zagros Basin, SW Iran

A rich assemblage of planktonic foraminifera has been studied from an outcrop of the Gurpi Formation, the hydrocarbon source rock in the southwest Iran, Deh Dasht area (Kuh-e Siah anticline). Based on the distribution of the planktonic foraminifera, eight biozones have been recognized that included: Dicarinella concavata Interval Zone (Earliest Santonian), Dicarinella asymetrica Total Range Zone (Santonian to Earliest Campanian), Globotruncanita elevata Partial Range Zone (Early Campanian), Globotruncana ventricosa Interval Zone (Middle to Late Campanian), Radotruncana calcarata Total Range Zone (Late Campanian), Globotruncanella havanensis Partial Range Zone (Late Campanian), Globotruncana aegyptiaca Interval Zone (Late to latest Campanian), Gansserina gansseri Interval Zone (Latest Campanian to Early Maastrichtian). These biozones indicates that the Gurpi Formation deposited during the Early Santonian- Early Maastrichtian. These biozones are compared to the most standard biozones defined in Tethysian domain. Based on distribution of morphotype groups of planktonic foraminifera, planktonic to benthic ratio (P/B) and content of carbonate, nine third-order sequences are recognized.

Late Cretaceous-Early Paleogene (Turonian? to early Danian) planktic foraminifera from DSDP site 356: a biostratigraphic reappraisal

Biostratigraphic results obtained with a systematic study of the planktic foraminiferal assemblages recovered from Upper Cretaceous-Lower Paleogene strata (Turonian? to early Danian in age) of Deep Sea Drilling Program (DSDP) Site 356, Sao Paulo Plateau, are presented and discussed herein. Fifty-nine planktic foraminiferal species were identifi ed within the studied interval, enabling the identifi cation of 11 planktic foraminiferal zones (Turonian? to early Danian in age): Marginotruncana schneegansi, Dicarinella concavata, Dicarinella asymetrica, Globotruncanita elevata, Contusotruncana plummerae, Radotruncana calcarata, Globotruncanella havanensis, Pseudoguembelina palpebra, Abathomphalus mayaroensis, Pseudoguembelina hariaensis and Pα. An unconformity spanning at least 0.96 Ma could also be suggested within core 31 (Maastrichtian in age), due to the absence of the Racemiguembelina fructicosa Interval Zone from the studied section. High sedimentation rates were estimated within the Santonian (Dicarinella asymentrica Total-range Zone) and the uppermost Maastrichtian (Pseudoguembelina hariaensis Interval Zone) of DSDP site 356, while lower and more constant values were suggested for the Campanian-lower Maastrichtian interval (Globotruncanita elevata Partial-range Zone to Pseudoguembelina palpebra Interval Zone). The reliability in identifying the Contusotruncana plummerae Interval Zone (Campanian in age) in Cretaceous sections of the South Atlantic Ocean is confi rmed herein.

Late Coniacian- Early Campanian planktonic foraminiferal bioevents and biostratigraphy of the northern Tunisia

Planktonic foraminifera were quantitatively analyzed across the Upper Coniacian - Lower Campanian succession at Jebel Ennahli and Ettout sections, northern Tunisia. This succession is characterized by hemipelagic facies domainated by a continuous sedimentary succession, allowing a good biostratigraphic correlation for this time interval. 55 planktonic foraminiferal species have been identified belonging to 13 genera. The distribution pattern of 17 heterohelicids and 38 trochospiral forms reveals to the identification of12 major bio-events and establishing three zones based on heterohelicids and five zones based on trochospiral forms. The trochospiral based zones are from base to top: Dicarinella primitiva Interval Zone, Dicarinella concavata Interval Zone, Dicarinella asymetrica Total Range Zone, and Globotruncanita elevata/Globotruncana arca Concurrent Range Zone, Globotruncana ventricosa Interval Zone; while the three heterohelicid based planktonic foraminiferal biozones are: Pseudotextularia nuttalli Interval Zone, Sigalia carpatica Interval Zone, Ventilabrella eggeri/Planoglobulina manuelensisConcurrent Range Zone. The bioevents and planktonic foraminiferal zones were correlated with the previously published works especially in Tunisia and other palaeolatitude provinces. There are no significant planktonic foraminiferal datums recorded across the Coniacian/Santonian boundary (CSB) except the lowest occurrence (LO) of Dicarinella asymetrica, which was recorded slightly below the LO of inoceramid Platyceramus cycloides cycloides representing a good proxy for the CSB. The Santonian/Campanian boundary of the studied sections are characterized by a major turnover represented by the highest occurrence of Sigalia, Dicarinella and Whiteinella genera; in addition to the lowest occurrence of Ventilabrella and Planoglobulina genera and above slightly the LO Globotruncana and Globotruncanita.

Planktonic foraminiferal biostratigraphy and paleoecology of Upper Cretaceous deposits from the Palmyride Region, Syria

Planktonic foraminifera were quantitatively analyzed across the Upper Coniacian - Lower Campanian succession at Jebel Ennahli and Ettout sections, northern Tunisia. This succession is characterized by hemipelagic facies domainated by a continuous sedimentary succession, allowing a good biostratigraphic correlation for this time interval. 55 planktonic foraminiferal species have been identified belonging to 13 genera. The distribution pattern of 17 heterohelicids and 38 trochospiral forms reveals to the identification of12 major bio-events and establishing three zones based on heterohelicids and five zones based on trochospiral forms. The trochospiral based zones are from base to top: Dicarinella primitiva Interval Zone, Dicarinella concavata Interval Zone, Dicarinella asymetrica Total Range Zone, and Globotruncanita elevata/Globotruncana arca Concurrent Range Zone, Globotruncana ventricosa Interval Zone; while the three heterohelicid based planktonic foraminiferal biozones are: Pseudotextularia nuttalli Interval Zone, Sigalia carpatica Interval Zone, Ventilabrella eggeri/Planoglobulina manuelensis Concurrent Range Zone. The bioevents and planktonic foraminiferal zones were correlated with the previously published works especially in Tunisia and other palaeolatitude provinces. There are no significant planktonic foraminiferal datums recorded across the Coniacian/Santonian boundary (CSB) except the lowest occurrence (LO) of Dicarinella asymetrica , which was recorded slightly below the LO of inoceramid Platyceramus cycloides cycloides representing a good proxy for the CSB. The Santonian/Campanian boundary of the studied sections are characterized by a major turnover represented by the highest occurrence of Sigalia , Dicarinella and Whiteinella genera; in addition to the lowest occurrence of Ventilabrella and Planoglobulina genera and above slightly the LO Globotruncana and Globotruncanita .