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

In 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.

Geochemical characteristics from tests of four modern planktonic foraminiferal species in the Indonesian Throughflow region and their implications

Test geochemistry of planktonic foraminifera is an indispensable tool in reconstructing past ocean hydrological changes. It is essential to investigate region-specific implications of test geochemistry,although those established from other regions can be broadly applied. In this study, characteristics of6180 and Mg/Ca from tests of four planktonic foraminiferal species, Globigerinoides ruber sensu stricto(s.s.), Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, from 60 coretop sediment samples retrieved from the Indonesian Throughflow(ITF) region were studied. These geochemical data were compared with modern hydrographic profiles in order to assess their relations and to investigate potential implications of test geochemical parameters in reconstructing past oceanographic change in the ITF region. Calcification depths of these four species were first estimated based on comparison between measured test δ180 and predicted calcite δ^(18)O that was calculated from modern temperature and salinity. The results indicate that G. ruber s.s. and G. sacculifer calcify within the mixedlayer at 0-50 m and 20-75 m, respectively, whereas P. obliquiloculata and N. dutertrei calcify within the thermocline at around 75 to 125 m. A combined study of excess Mg/Ca(difference between measured and predicted Mg/Ca) and salinity suggests that salinity exerts a negligible impact on test Mg/Ca of these foraminiferal species in the ITF region. Comparison of test Mg/Ca-derived temperatures with temperature profiles of the upper 200 m of the water column from the seas of the ITF region also indicate calcification depths of these species, which match well with the above estimations using test δ^(18)O. It further indicates that G. sacculifer may be more sensitive in reflecting changes in the depth of the mixedlayer, highlighting a potential use of Mg/Ca temperature difference between G. ruber s.s. and G. sacculifer in reconstructing the depth of the mixed-layer in the ITF region.

Planktonic Foraminiferal Assemblage Variations of Ontong-Java Plateau during Late Quaternary and Their Implications for Paleotemperature in the Western Pacific Warm Pool

Ocean Drilling Program (ODP) Site 807A was recovered from the Ontong-Java plateau, western equatorial Pacific. Quantitative analysis of planktonic foraminifera, combined with oxygen and carbon isotope data, reveals the glacial-interglacial variations of sea-surface temperature and the upper water vertical structure in this region during the late Quaternary. Our results indicate that since 530 ka sea-surface temperature (SST) and the depth of thermocline (DOT) have changed significantly in the western Pacific warm pool (WPWP). The average glacial-interglacial annual SST difference was up to 4.2 ℃, and the DOT fluctuations could exceed more than 100 m, further suggesting the instability of the WPWP. The spectral analyses of SST and DOT reveal two dominating cyclicities—the typical 100 ka cycle and the semi-precessional cycle, which is significant in the tropical spectrum, indicating that late Quaternary paleoceanographic changes in the study area were influenced not only by a high latitude forcing but also by tropic-driving factors.

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).

The evolution of the Kuroshio Current over the last 5 million years since the Pliocene: Evidence from planktonic foraminiferal faunas

Meridional heat transport of the western Pacific boundary current(the Kuroshio Current)is one of the key factors in global climate change.This current is important because it controls the temperature gradient between low latitudes and the North Pacific and so significantly influences mid-latitude atmosphere-ocean interactions.Here we reconstruct changes in hydrological conditions within the mid-latitude mainstream of the Kuroshio Current based on faunal analysis of planktonic foraminifera in core DSDP 296 from the Northwest Pacific Ocean.This approach enabled us to deduce evolutionary processes within the Kuroshio Current since the Pliocene.A total of 57 species in the coarser section(>150μm)were identified;results indicate that planktonic foraminiferal faunal evolution has mainly been characterized by three major stages,the first of which comprised mixed-layer warm-water species of Globigerinoides ruber which first appeared between 3.5 and 2.7 Ma and then gradually increased in content.Percentages of another warm-water species of G.conglobatus also gradually increased in number over this interval.Variations in warm-water species indicate a gradual rise in sea surface temperature(SST)and imply initiation of Kuroshio Current impact on the Northwest Pacific Ocean since at least 3.5 Ma.Secondly,over the period between 2.7 and 2.0 Ma,thermocline species of Globigerina calida,Neogloboquadrina humersa,Neogloboquadrina dutertrei,and Pulleniatina obliquiloculata started to appear in the section.This fauna was dominated by G.ruber as well as increasing G.conglobatus contents.These features imply a further rise in SST and its gradually enhanced influence on thermocline water,suggesting strengthening of the Kuroshio Current since 2.7 Ma.Thirdly,between 2.0 Ma and present,increasing contents of thermocline species(i.e.,G.calida,N.dutertrei and P.obliquiloculata)indicate a gradual rise in seawater temperature at this depth and also imply more intensive Kuroshio Current during this period.On the basis of comparative records from cores ODP 806 and DSDP292 from the low latitude Western Pacific,we propose that initiation of the impact of the Kuroshio Current in the Northwest Pacific and it subsequent stepwise intensifications since 3.5 Ma can be closely related to the closure and restriction of the Indonesian and Central American seaways as well as variations in the Western Pacific Warm Pool(WPWP)and equatorial Pacific region.

Miocene Pliocene planktonic foraminiferal biostratigraphy of the Pearl River Mouth Basin,northern South China Sea

The present study deals with the planktonic foraminiferal biostratigraphy of the Miocene-Pliocene sequence of three petroleum exploration wells (BY7-1-1,KP6-1-1 and KP91-1) in the Pearl River Mouth Basin (PRMB).In general,the three wells contain a fairly well-preserved,abundant foraminiferal fauna.The proposed planktonic foraminiferal zonation follows the scheme updated by Wade et al.(2011).Nineteen planktonic foraminiferal zones have been recognized,14 zones (zones M1-M14) for the Miocene and 5 zones (zones PL1-PL5) for the Pliocene.The zonation is correlated with previously published biostratigraphic subdivisions of the Neogene succession in the PRMB and with international foraminiferal zonations.The zonal boundaries are mostly defined by the last appearance datum of zonal taxa of planktonic foraminifera,which is more reliable than the FAD (first appearance datum) events for ditch cutting sampling.Changes in the coiling of Globorotalia menardii (s.l.) are also used to define the zonal boundaries,where no LADs (last appearance datum) are available.The Fohsella fohsi group,comprising useful taxa for delimiting zonal boundaries of the middle Miocene in other areas,has a poor record within the Pearl River Mouth Basin due to unfavorable ecological conditions,and cannot be used for the studied wells.Different from the previously reported zonal scheme for the PRMB,the present zonation is based on correlation with the current standard planktonic foraminiferal zonation,with calibrated absolute ages.

Planktonic foraminifera as bio-indicators for monitoring the climatic changes that have occurred over the past 2000 years in the southeastern Tyrrhenian Sea

A high-resolution integrated study has been performed in a super-expanded marine record(sedimentation rate spanning from 11 cm/100 years to 20 cm/100 years)from the continental shelf area of the southeastern Tyrrhe­nian Sea.Planktonic foraminiferal distribution illustrates 6 major environmental changes during the past 2000 years:(i)the Roman Period-Dark Age transition(from herbivorous-opportunistic to carnivorous species);(ii)the Dark Age-MCA transition(from carnivorous to herbivorous-opportunistic species);(iii)the Medieval Clas­sic Anomaly-Little Ice Age transition(a further and definitive change from carnivorous to herbivorous-opportunistic species);(iv)the period during the Maunder event between approximately 1720 AD and 1740 AD(turnover from the carnivorous planktonic foraminifer Globigerinodes ruber to the herbivorous-opportunistic planktonic foraminifer Turborotalita quinqueloba);(v)the Industrial Period(dominance of herbivorous-opportunistic planktonic foraminifera);and(vi)the Modern Warm Period at approximately 1940 AD(the last turnover in favor of herbivorous-opportunistic planktonic foraminifers,associated with an increase in benthic foraminifera).Our studies lead us to link this latter feature to an anthropogenic impact associated with the dam­ming of Sele River(Salerno Gulf)at 1934 AD,which induced a change in the sediment input with a strong de­crease in coarse-grained fraction and a probable alteration in nutrient supply.Theδ^(18)O_(G.ruber) record of the past 2000 years shows the alternation of warm/wet and cold/dry events related to the Roman Period,the Dark Age,the Medieval Classic Anomaly,the Little Ice Age,the Industrial Period and the Modern Warm Period.The 5 ev­identδ^(18)O_(G.ruber) oscillations(between approximately 1325 AD and 1940 AD)coincide with the 5 minima in the solar activity record(Wolf,Spörer,Maunder,Dalton and Damon events).

Late Cretaceous Foraminiferal Faunas from the Saiqu“mélange”in Southern Tibet

As one of the mélanges in the southern side of the Yarlung-Zangbo suture zone, the Saiqu mélange in southern Tibet is important for understanding the evolution of the Neo-Tethys ocean. The age of the Saiqu mélange, however, has been debated due to the lack of reliable fossil evidence in matrix strata. Based on lithological similarities with platform strata in southern Tibet and limited fossils from exotic blocks, previous studies variously ascribed the Saiqu mélange to be Triassic in general, Late Triassic, or Late Cretaceous. Here we reported planktonic foraminiferal faunas from the matrix strata of the Saiqu mélange. The new fossils yield a Late Cretaceous age, which is so far the best age constraint for the mélange. Regional stratigraphic correlation indicates that the Cretaceous Oceanic Red Beds （CORBs） in Saiqu may be time equivalent to the CORBs of the Zongzhuo Formation in neighboring regions. Thus the Saiqu m^lange should be correlated to the Upper Cretaceous Zongzhuo Formation rather than the Triassic Xiukang Group, as previously suggested.

Paleoceanographic events of the southern Okinawa Trough during last 20 000 years

Two hteh resolution down-cores (92-255, 92-170) are used to study the Palaxeanographic events of the southern Okinawa Trough during the last 20 000 years. Planktonic foraminifera are quantitatively analyzed and three paleoceanographic events are recognized. Glacial/post-glacial variations in sea surface temperature (SST), water masses and upper water column structure are the most important environmental changes recorded by planktonic foraminifera. There is also an abrupt climatic event (about 10 710~ 9 170 a BP) during the Termination I, planktonic foraminifera (PF) δ18 O and SST have a same return pattern, but benthic foraminifera (BF) δ18 O doesn' t have.therepancy between PF δ18 O and BF δ18 O may reflect that the sea suriace water is more sensitive to abrupt, short term environmental change than the sea bottom water. High-resolution strata aIso suggest a middle- Holocene Pulleniatina obliquifoculata minimum event.

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.

Micropaleontology and Biostratigraphy of Zgaimat Al-Hasah Anticline, SE-Jordan

This study presents the first attempt to recognize the planktonic foraminiferal biozones and to determine the time of deposition of the carbonate deposits exposed in the Zgaimat Al-Hasah anticline, Southeastern Jordan. Five equivalent planktonic foraminiferal biozones;Zones E3 (P6a), E4 (P6b), E5 (P7), E6 (P8), and E7 or E7a were identified by analyzing twenty-eight samples from a 20 m thick section. Ten planktonic foraminiferal species belonging to seven genera and thirteen benthic foraminiferal species representing eleven genera were recorded. An Early Eocene age was assigned to the carbonate deposits exposed in Zgaimat Al-Hasah anticline based on some typical index species of calcareous planktonic foraminifera.