Neritic Marine Environment Research Articles

Macrofossil Characteristics and Bathymetric Environment of Sumber Makmur Village, Muara Sahung, Kaur, Bengkulu

The research location is administratively located in Sumber Makmur Village, Muara Sahung District, Kaur Regency, Bengkulu Province. In the study area, outcrops that had fossils were found, which were shown by the presence of carbonate rock lithology. The study was conducted to determine the deposition environment in the research area. The method used is a previous literature study that aims to determine the physical geological conditions and regional stratigraphy of the research area. Furthermore, field observations and laboratory analysis were conducted in the form of paleontological analysis to determine the characteristics and types of fossils found in the study area. Paleontological research was conducted on two formations, namely the Lemau Formation and the Simpangaur Formation. In the Lemau Formation, several species of benthic foraminifera were found, namely Cibicides praecinestus, Elphidium macelium, Marginopora vertebralis, Elphidium articulatum, and Planorbulina mediterranensis. Then, in the Simpangaur Formation, several species of benthic foraminifera were found, namely Streblus beccari, Bolivina schwageriana, Anomalinella rostrate, Cibides praecinestus, Cibides margaritiferus, Lagena sulcata, Quinqueloculina bradyana, and Lenticulina calcar. In addition, macrofossils were found in marine life with phylum mollusks such as Lunatia elevatum, Murex vanuxemi, Turritella terebra, Conus sauridens, and Plocostoma neumayeri. Based on these data, it can be interpreted that the depositional environment in the study area is in the Transition-Edge Neritic marine environment.

Age of the latest marine sedimentation in the western Kunlun area constrained by planktic foraminifera

Surface uplift of the Tibetan Plateau in the Cenozoic has dramatically affected evolutions of climate, environment, and biota in East Asia. The onset time of plateau uplift can be roughly constrained by the termination of the latest marine sedimentation, which shows large spatial differences in the Tibetan Plateau. In the northwest Tibetan Plateau of the western Kunlun area, the Tielongtan Group represents the latest marine sedimentation. However, the age of its depositional cessation is still unknown. For the first time, we conduct taxonomic, paleoecologic and paleogeographic studies of planktic foraminifera in the limestones of the Tielongtan Group. Despite poor preservation and low abundance, ten planktic foraminiferal species are identified, including Globotruncana falsostuarti, G. cf. linneiana, G. cf. ventricosa, Planohedbergella prairiehillensis, P. cf. yaucoensis, Pseudotextularia nuttalli, Planoheterohelix globulosa, P. cf. praenuttalli, Muricohedbergella holmdelensis and Whiteinella brittnensis. The foraminiferal assemblages suggest an age of late Campanian to Maastrichtian, indicating a shallow, neritic marine environment. Combining available research data from other regions, we show that these planktic foraminifera were widely distributed in the Tarim basin, southern Tibet, and the Mediterranean area during the latest Cretaceous. Our result of planktic foraminifera in the Tielongtan Group implies that the surface uplift of the western Kunlun area did not begin until after ∼76–66 Ma.

Sedimentology and foraminiferal paleoecology of the exposed Oligocene–Miocene Ogwashi-Asaba Formation in Issele-Uku area, Anambra Basin, southern Nigeria: A paleoenvironmental reconstruction

Sedimentological and foraminiferal paleoecological studies were carried out for the Oligocene–Miocene Ogwashi-Asaba Formation of the Anambra Basin at the Issele-Uku area in southern Nigeria, to reconstruct paleoenvironments. The pattern of rock successions and textural characteristics suggest the prevalence of fluvio-deltaic setting during the formation of lignites and clastic rocks of Ogwashi-Asaba Formation. Agglutinated benthic foraminiferal species such as Ammotium sp., Textularia sp., Gavelinella sp., Milliamina sp., Reophax sp., Bolivina sp., Eponides sp., Pseudobolivina sp. and Lenticulina sp. dominate the shale units whereas the planktonic forms are absent. All these species have very low population and diversity in the shales, which could be due to the presence of harsh conditions such as low oxygen level and scarcity of food, leading to poor survival. The assessments of benthic foraminifera's habitat suggest middle-to-inner neritic marine environment for the shales. Granulometric results suggest fluvial environment for the sandstone and deltaic for the lignite. The Ogwashi-Asaba Formation in Issele-Uku area of Anambra Basin, southern Nigeria, therefore, have records of shallow marine, and fluvio-deltaic paleoenvironments.

A snapshot into the Oligocene vegetation of the Tethyan southern shores: new fossil pollen evidence from North Africa (Egypt)

A palynological investigation was carried out on 24 samples from the Oligocene Dabaa Formation, which cuts across the Amana-1X well, located in the Abu El Gharadig Basin, north Western Desert, Egypt. Palynological evidence presented here suggests an early Oligocene age for the studied Dabaa Formation. In addition, the palynological assemblages provide supplementary evidence for depositional environments. They are generally indicative of outer-shelf to upper slope environment under oxic to anoxic conditions for the lower part of the studied Dabaa Formation, but infrequent occurrences of more diverse assemblages suggest an inner neritic marine environment for strata at some levels in the upper part of the studied section. It was during the Oligocene that marked floral changes leading to the development of modern plant associations began such as temperate deciduous forests (with e.g., Acer and Betulaceae) which expanded greatly in the mid latitudes. A distinctive vegetational pattern could be outlined within the deposition of the Dabaa Formation. This pattern includes mangroves represented by taxa such as Zonocostites ramonae, Psilatricolporites crassus and Verrucatosporites usmensis. Another considerably different association with plenty of the freshwater algae Botryococcus and Pediastrum spp. at this level or tropical forests at slightly elevated altitudes (ever wet climate) are dominated by a variety of tropical forest taxa including Malvaceae and Striatricolpites, together with Retitricolporites irregularis, Psilatricolporites operculatus, Retibrevitricolporites ibadanensis, Retitricolporites spp. and Psilamonocolpites spp. in addition to ferns and tree ferns where tropical floras dominate. Also recognized are elements of savanna or open woodland (less humid climate) taxa like Poaceae pollen (grass) such as Monoporopollenites annulatus associated with Amaranthaceae (e.g., Chenopodipollis multiplex), Cyperaceae spp., Echiperiporites estelae, Proteacidites cooksonii, Cicatricosisporites dorogensis and Pteris. Finally, the montane ecosystems may have occurred at the slopes of mountains including rare pollen assigned to Sapotaceae (Psilastephanocolporites spp.) and Anacardiaceae (Retitricolpites simplex) which are probably part of the palynoflora due to long-distance transport.

Palaeoevironmental reconstruction based on palynomorphs from the upper Oligocene San Gregorio Formation (core LB1), in a semiarid coastal marine setting, Baja California Sur, Mexico

Terrestrial and marine palynomorph assemblages from a total of 42 productive samples from San Gregorio Formation core LB1 were analysed. Marine palynomorphs, such as dinocysts, acritarchs, copepod eggs, among others, dominated the associations. With regard to terrestrial palynomorphs, dicotyledonae (e.g. Anacardiaceae type, Chenopodipollis spp., Brossipollis spp., Euphorbiaceae type, Fabaceae type, Quercoidites sp., Polygonaceae type and Sterculiaceae type) were more abundant than monocotyledonae (e.g. Liliacidites spp. and Graminidites sp.). The recovered palynoflora gave evidence of two temperate highland communities: Pinus forest and cloud forest. Furthermore, representatives of the local semiarid vegetation (Brossipollis, Chenopodipollis, Ephedripites and Graminidites), growing throughout a palaeoaltitudinal gradient from the uplands down to the shoreline, such as chaparral, tropical deciduous forest, coastal grassland and coastal dune also occurred. Terrestrial taxa richness varied between 5 and 57, the diversity index ranged between 1.2 and 3, and evenness oscillated between 0.4 and 1. As for marine palynomorphs, the dominant dinoflagellate cysts were Cleistosphaeridium sp., Cordosphaeridium sp., Chiropteridium lobospinosum, Homotryblium sp., Hystrichokolpoma rigaudiae, Lingulodinium machaerophorum, Operculodinium centrocarpum, Polysphaeridium sp. and Spiniferites spp., suggesting that San Gregorio Formation core LB1 was deposited in a neritic marine environment. The dinocysts Chiropteridium lobospinosum and Tuberculodinium vancampoae support a late Oligocene age for the San Gregorio Formation at LB1. Marine taxa richness oscillated between 5 and 18, the diversity index ranged from 0.2 to 2.4 and evenness fluctuated between 0.1 and 0.9. CONISS statistical analysis of the terrestrial and marine palynomorphs allowed us to group the SGF assemblages into four palynozones.

Preliminary late Miocene palynomorph assemblages from the Quifangondo and Luanda formations, Onshore Kwanza Basin, Angola

A Miocene succession exposed at the Cabo Ledo and Miradouro da Lua sections in the Onshore Kwanza Basin, Angola, was examined for palynology. Palynomorphs of preliminary late Miocene age identified are presented herein. The upper part of the Quifangondo Formation is dated as middle Tortonian in age based on the co-occurrence of the pollen grain Fenestrites spinosus and the dinoflagellate species Selenopemphix armageddonensis. The palynomorph signature indicates a middle neritic marine environment dominated by dinoflagellate cyst taxa.A late Miocene (late Tortonian to Messinian) age is also documented for the first time at the base of the Luanda Formation based on the co-occurrence of the pollen taxa Echitricolporites spinosus, Fenestrites spinosus, Fenestrites longispinosus, Monoporopollenites annulatus, and Retistephanocolpites gracilis. The palynomorph signature of this unit reflects an inner neritic marine (coastal/lagoon transitional) environment dominated by terrestrial palynomorphs and very rare dinoflagellate cyst taxa.The present research contributes data for improving the stratigraphical framework of the Quifangondo and Luanda formations, both of which are recognized as the main potential source rocks and reservoirs of the Post-Salt Paleogene/Neogene Petroleum System of the Kwanza Basin. This significant contribution provides important biostratigraphic and palaeoenvironmental data for defining the vital temporal horizons of these settings in a basin where petroleum exploration is of interest.

Biostratigraphy and paleoenvironments of the Pelotas Basin, southernmost Brazil, using Miocene dinoflagellate cysts

Dinoflagellate cysts assigned to the subfamily Protoperidinioideae are frequently recorded in Miocene coastal deposits, and their relative abundance is directly related to primary productivity and favorable post depositional conditions. However, these microfossils are poorly studied in Brazilian Miocene sequences. This paper presents the results of a palynological study on 18 samples obtained from the core CBM001-ST-RS drilled in the coastal plain of southernmost Brazil, related to the Cidreira Formation, Pelotas Basin. Forty-nine taxa are identified, 46 dinoflagellate cysts, two genera of chlorophyte algae, and one acritarch species. Overall, the samples are characterized by large numbers of Spiniferites spp. and Brigantedinium spp., as well as a significant richness of the subfamily Protoperidinioideae. Several species of dinoflagellate cysts indicate a Miocene age, but the record of Sumatradinium hamulatum and Quadrina? condita restricts the age of the interval analyzed to the middle Miocene. Both the PMI and the P/G palynological indices indicate a neritic marine environment and moderate primary productivity, respectively.

Late Aptian to early Cenomanian dinoflagellate cysts from Agadir Basin, southwestern Morocco: Biostratigraphy and palaeoenvironment

The Agadir Basin (Moroccan Atlantic margin) is characterized by its fossil richness, including organic-walled microfossils. The palynological analysis of the middle Cretaceous succession from the Tamzargout section and EGA.1 well reveals the presence of well-preserved and diverse assemblage, rich in dinoflagellate cysts. The assemblages contain stratigraphic marker taxa and show significant chronostratigraphic events. Based on these bioevents and on the comparison with different palaeogeographic domains, a determination of age was proposed. The biogeographic characteristics of most cosmopolitan taxa in this study confirm the establishment of new oceanic communication related to the opening of the equatorial Atlantic. The Albian-Cenomanian transition has been recognized only in EGA.1 well, whereas the Aptian-Albian transition, the early-mid Albian and the mid-late Albian have been defined in both the section and the well. The recorded associations are comparable to those of neighboring deposits and those of the Tethyian and Atlantic domains. The vertical distribution of the organic matter in the sediments of the Agadir Basin and the compilation of all palaeoenvironmental proxies allowed identifying an Albian transgression with specific palaeoenvironments in each interval. Neritic marine environments alternated with short phases of continental and oceanic influence is deduced for the late Aptian-early Cenomanian in this basin. The late Aptian-early to mid Albian recorded an outer neritic palaeoenvironment under oceanic influence; the mid to late Albian showed littoral conditions during a regressive phase fluctuating to middle to outer neritic environment; finally the late Albian-early Cenomanian transition was characterized by a middle neritic palaeoenvironment under coastal influence.

Seismic characteristics and strontium isotope ages of the Middle Miocene Ngrayong Formation in the Madura Strait Basin: Implications for the paleogeographic reconstruction of East Java

East Java, on the southeastern margin of the Sundaland Shelf, is an ideal and pilot location to study paleogeographic changes due to the interactions of the Eurasian and the Indian-Australia plates. Many studies have been conducted; however, some issues remain poorly understood, such as the initial compression stage and associated paleogeography of East Java. Here, we report newly acquired high-resolution seismic data and drilling wells in the area of the Madura Strait. We systematically reconstruct a three-dimensional model on the paleogeography of East Java in the Middle Miocene in combination with others’ results. Different depositional environments and characteristics of the related lithofacies observed on both sides of the Middle Miocene volcanic arc imply that weak subaerial and subaqueous volcanism existed in East Java. The extensive Ngrayong fining in the southward clastic sequences, located north of the mentioned volcanic arc, were deposited in a bathyal marine environment, which showed an oversteepening slope and basinal characteristics with outer neritic to bathyal facies within the present-day Kendeng Zone and Madura Strait area. This differs from the northern region of the present-day Rembang-Madura Inversion Zone and the northern offshore region of East Java, which were deposited in a transitional and neritic marine environment. We identified two new turbidite fans showing opposite source directions based on 3D seismic data within the Madura Strait area. Four controlling factors contributed to the formation of the Ngrayong turbidite fans, including the paleotopography of the underlying Kujung Formation, short-term intense regional tectonic events, high rates of sediment supply and occasional volcanic activity.

Dinoflagellate cyst evidence for the age, palaeoenvironment and paleoclimate of a new Cretaceous–Paleogene (K/Pg) boundary section at the Bou Angueur syncline, Middle Atlas, Morocco

In this paper, we present results of a palynological analysis of the phosphate succession from the northern flank of the Bou Angueur syncline in the Middle Atlas (central Morocco). The studied interval yielded a well-preserved and diverse palynological content, dominated by dinoflagellate cysts (dinocysts), allowing a detailed taxonomic study of dinocyst and a new biostratigraphic dating of the section. The studied section is assigned to the upper Maastrichtian–Danian interval. A new, relatively complete K/Pg boundary transition was recognized. The succession at the Bou Angueur syncline was compared to Tethyan K/Pg boundary sections, such as the K/Pg boundary Global Stratotype Section and Point (GSSP) at El Kef (NW Tunisia) and Ouled Hadou section (NE Morocco). The dinocyst marker events used for the identification of the late Maastrichtian include the first occurrences of Cordosphaeridium inodes subsp. inodes, Deflandrea galeata and Glaphyrocysta perforata and those used for the early Danian include the first occurrences of Carpatella cornuta, Cassidium fragile, Danea californica, Lanternosphaeridium reinhardtii and Senoniasphaera inornata.The organic-walled dinocyst-producing dinoflagellates did not undergo the K/Pg mass extinction resulting from a large meteoritic impact. They enable us to interpret the environmental and climatic changes in the earliest Danian, while calcareous microfossils could not, since they are partially or completely extinct. We thus describe seven palynological assemblages, reflecting paleoenvironmental and paleoclimatic changes, inferred from changes in relevant ecological parameters, including changes in the relative abundance of selected dinocyst groups, often used as paleoenvironmental indicators. An inner to middle neritic marine environments alternated with several short phases of more offshore conditions is deduced for the late Maastrichtian and earliest Danian and an open outer neritic marine environment during a transgressive regime in the latest Danian. Several dinocyst events were recognized in the studied interval, among which remarkable blooms of tropical warm-water and high-latitude cold-water dinocyst taxa are interpreted herein as ecological responses, related to global climatic changes, including a global warming episode during the late Maastrichtian and the well-known brief global cooling following the K/Pg boundary Chicxulub impact.

Middle Eocene to early Oligocene dinoflagellate cyst biostratigraphy and paleoenvironmental interpretations of the Ben Attaya section at Taza, eastern External Rif, Morocco

The palynological study was carried out on middle Eocene to early Oligocene sediments from the Ben Aattaya section, located in the Taza region, eastern External Rif, northeastern Morocco. The palynological content is dominated by dinoflagellate cysts (dinocyst), while spores and pollen are rare. Very known dinocyst event markers were used for dating the Ben Attaya section. The first occurrences (FO) of Cerebrocysta bartonensis, Glaphyrocysta semitecta, Lentinia serrata, Operculodinium divergens indicate the Bartonian. The FOs of Deflandrea heterophlycta, Schematophora speciosa, Stoveracysta ornata were used to recognize the Priabonian. While the FOs of Chiropteridium lobospinosum and Wetzeliella gochtii, as well as the last occurrences (LO) of Achilleodinium biformoides, Charlesdowniea coleothrypta subsp. coleothrypta, Enneadocysta pectiniformis, Glaphyrocyst semitecta, Hemiplacophora semilunifera, Lentinia serrata, Operculodinium divergens, Rhombodinium perforatum, Schematophora speciosa and Stoverocysta ornata highlight the Rupelian. The changes in relative abundances of selected dinocyst groups and sporomorphs (pollen and spores) suggest a lagoonal to coastal inner neritic marine environment during the Bartonian and Priabonian, which was interrupted by a short phase of outer neritic conditions at the basal part of the section and ended by a marked decrease in the sea level, probably due to a regression during the Priabonian. The Rupelian deposits indicate a middle neritic marine environment marked by a progressive rise during the transgression.

Palynological and palaeoenvironmental analyses of the upper Albian-Cenomanian succession in Gindi Basin, Egypt: Implication for transgressive/regressive systems tracts

The current contribution illustrates the advantage of the use of quantitative palynological data to palaeoenvironmentally differentiate the similar-looking monotonous, thick clastic interval of the Kharita, Bahariya and Abu Roash “G” units in Gindi Basin, Egypt. The present study aims also to the utilization of the upper Albian-Cenomanian quantitative palynological and palynofacies data and their integral interpretation in a sequence stratigraphic context. The recovered palynomorph assemblages with moderately diverse sporomorphs and dinoflagellate cysts, show poor to fair preservation. Around 47 species of pollen grains, 37 of dinoflagellate cysts and 36 species of pteridophytic spores have been recorded from two sections encountered in El Sagha-1A and BRE 6-1 wells drilled in Gindi Basin; however, achritarchs, microforaminiferal test linings and freshwater algae are impoverished and sparsely documented through the studied intervals. Based on the first downhole appearances (FDAs) of the recovered marker taxa, the encountered Abu Roash “G”, Bahariya and the upper Kharita units are palynologically dated as late Cenomanian, early-middle Cenomanian and late Albian, respectively. Relative sea level fluctuation is particularly relevant and deduced from various palynological parameters mainly the terrestrial:marine (T:M) ratio and the palynological marine index (PMI). Based on the vertical stratigraphic distribution of the palynofacies along with the relative variations of the terrestrial versus marine palynomorphs, five complete (SQ1-SQ5) third order transgressive-regressive sequences and incomplete one are defined in El Sagha-1A in comparison to six complete (SQ2-SQ7) and one incomplete (SQ1) are constructed in BRE 6-1. Reliance on distinctive palynofacies assemblages, differentiated based on the relative composition of particulate organic matter constituents, four depositional palaeoenvironments were interpreted for the studied intervals. The Kharita and Bahariya formations were elucidated to be deposited in fluctuating marginal-shallow and proximal inner neritic marine environments. However, the sea level remarkably showed a continued rising which brought the inner-middle neritic conditions of the Abu Roash “G” Member during late Cenomanian.

Middle Miocene ostracods from Wadi Sudr, westcentral Sinai, Egypt: systematic, biostratigraphy and palaeobiogeographic affinity with the Mediterranean realm

The investigation of the exposed middle Miocene strata from Wadi Sudr yielded well-preserved ostracod carapaces. Detailed taxonomic and paleontological studies led to the recognition of 36 ostracod species belonging to 25 genera, 4 species of them were considered new which fully described. Three assemblage biozones were recorded as follows: Actinocythereis spinosa–Actinocythereis hystrix zone, Chrysocythere cataphracta muricata-Cytheretta africana zone, and Disopontocypris schweijeri-Bythocypris tripolensis zone. The recorded biozones were calibrated with the previously studied middle Miocene planktonic foraminiferal biozones on the same samples and also correlated with the Miocene ostracod biozones from the neighboring countries. Our ostracod assemblages present in the lower and upper parts of the studied section (section II) indicated an inner neritic marine environment of moderate energy of currents and rapid sedimentation, while the assemblages in the middle part showed more deeper (outer neritic) environments with low energy of currents and low rate of sedimentation. The palaeobiogeographic distribution of the studied ostracods showed high affinity with the ostracod assemblages of the southern Mediterranean and moderate to low affinities with that of the northern and eastern Mediterranean respectively. The highly ornamented ostracod species with structures on the carapace were recorded from both Northern and Southern Mediterranean, while the smooth ones were found in the Southern Mediterranean only. The highly ornamented species are more widely distributed in both Southern and Northern Mediterranean than the smooth species. This may indicate that the ornamented species are more able to migrate than the smooth ones.

Palynomorph stratigraphy, palynofacies and organic geochemistry assessments for hydrocarbon generation of Ratawi Formation, Iraq

Seventy-two core and cutting samples of the Ratawi Formation from selected wells of central and southern Iraq in Mesopotamian Foredeep Basin are analysed for their sedimentary organic matters. Dinoflagellates, spores and pollen are extracted by palynological techniques from these rocks. Accordingly, Hauterivian and late Valanginian ages are suggested for their span of depositional time. These palynomorphs with other organic matter constituents, such as foraminifer’s linings, bacteria and fungi, are used to delineate three palynofacies types that explain organic matter accumulation sites and their ability to generate hydrocarbons. Palaeoenvironments of these sites were mainly suboxic to anoxic with deposition of inshore and neritic marine environments especially for palynofacies type 2. Total organic matters of up to 1.75 total organic carbon (TOC) wt.% and early mature stage of up to 3.7 TAI based on the brown colour of the spore species Cyathidites australis and Gleichenidites senonicus with mottled interconnected amorphous organic matter are used for hydrocarbon generation assessment from this formation. On the other hand, these rock samples are processed with Rock-Eval pyrolysis. Outcomes and data calculations of these analyses are plotted on diagrams of kerogen types and hydrocarbon potential. Theses organic matter have reached the mature stage of up to T max = 438 °C, hydrogen index of up to 600 mg hydrocarbons for each gram of TOC wt.% and mainly low TOC (0.50–1.55). Accordingly, this formation could generate fair quantities of hydrocarbons in Baghdad oil field and Basrah oil fields. Organic matters of this formation in the fields of Euphrates subzone extends from Hilla to Nasiriyah cities have not reached mature stage and hence not generated hydrocarbons from the Ratawi Formation. Software 1D PetroMod basin modelling of the Ratawi Formation has confirmed this approach of hydrocarbon generation with 100 % transformations of the intended organic matters to generate hydrocarbons to oil are performed in especially oil fields of East Baghdad, West Qurna and Majnoon while oil fields Ratawi and Subba had performed 80–95 % transformation to oil and hence end oil generation had charged partly the Tertiary traps that formed during the Alpine Orogeny. Oil fields of Nasiriyah and Kifle had performed least transformation ratio of about 10–20 % transformation to oil, and hence, most of the present oil in this field is migrated from eastern side of the Mesopotamian Foredeep Basin that hold higher maturation level.

Callovian (Middle Jurassic) dinoflagellate cysts from the Algarve Basin, southern Portugal

The palynology of three Callovian (Middle Jurassic) limestone-marl successions from the Algarve Basin in southern Portugal was studied. These localities are Baleeira Harbour, Mareta Beach and Telheiro Quarry; they provide a composite. succession, tied to ammonite zones, through the Lower, Middle and Upper Callovian from the western and eastern subbasins of the Algarve Basin. The three sections generally yielded relatively abundant marine and continental palynofloras. Diversity is low to moderate and the dinoflagellate cyst associations are dominated by Ctenidodinium spp., the Ellipsoidictyum/Valensiella group, Gonyaulacysta jurassica subsp. adecta, Korystocysta spp., Meiourogonyaulax spp., Pareodinia ceratophora, Sentusidinium spp., Surculosphaeridium? vestitum and Systematophora spp. Some intra-Callovian marker bioevents were recorded; these include the range bases of Ctenidodinium ornatum, Gonyaulacysta eisenackii, Korystocysta pachyderma, Mendicodinium groenlandicum, Rigaudella spp. and Surculosphaeridium? vestitum. The occurrences of Endoscrinium acroferum and Impletosphaeridium varispinosum in the Early to Middle Callovian of Mareta Beach and Telheiro Quarry are also characteristic of this interval. At Baleeira Harbour, the presence of Ctenidodinium continuum and Gonyaulacysta centriconnata in the Peltoceras athleta Zone confirms the Late Callovian age of this section. The successions studied were deposited in restricted infralittoral neritic marine environments which lack deep water circulation, and possibly represent restricted embayments. The relatively low diversity nature of the dinoflagellate cyst assemblages appears to be largely due to the highly enclosed nature of this depocentre. Many Callovian index dinoflagellate cyst taxa which are found in northwest Europe are absent in the Algarve Basin. These forms may have been intolerant of enclosed palaeoenvironments which have restricted or no deep circulation. The Callovian marine palynofloras from the Algarve Basin compare well to the few other published records from the Iberian Peninsula of this age. However they are significantly less diverse than coeval floras from elsewhere in the extensive Mid Latitude Callovian phytoprovince. Many typically Callovian dinoflagellate cysts are cosmopolitan, however some provincialism is clearly manifested. The Arctic and Austral Callovian phytoprovinces are characterised by key endemic taxa such as Paragonyaulacysta retiphragmata and Ternia balmei, which are not present in the Algarve Basin and are assumed to have been polar forms.

Cretaceous–Lower Paleogene ostracods from the Pelotas Basin, Brazil

A total of 479 samples from five drill-holes of the Pelotas Basin were analysed. Despite the huge number of samples, only 98 specimens were recovered, belonging to nine families, 21 genera and 34 species (most in open nomenclature). Due to the paucity and poor preservation of this material, just seven taxa were identified or tentatively identified at the species level: Cytherella cf. C. araucana Bertels, Cytherelloidea spirocostata Bertels, Bairdoppilata triangulata Edwards, Actinocythereis indigena Bertels, Brachycythere gr. sapucariensis Krommelbein, Wichmannella araucana Bertels and Wichmannella meridionalis Bertels. Four taxa could not even be identified at the generic level and are referred as “gen. et sp. indet.”. Trachyleberididae and Cytherellidae were the most diversified and abundant families while Cytherella and Paracypris were the most diversified genera, with seven and four species, respectively. The K–Pg boundary in the Pelotas Basin is marked by a faunal change with the local disappearance of the genera Cytherelloidea, Argilloecia, Cythereis, Brachycythere, Pondoina and Rostrocytheridea, and the first local occurrence of Neonesidea?, Bairdoppilata, Ambocythere, Buntonia, Langiella?, Trachyleberis and Krithe. The genera Cytherella, Paracypris, Wichmannella and Actinocythereis are recorded in the Cretaceous as well as the Paleogene. This faunal study suggests a neritic marine environment for the analysed interval.

Miocene diatoms from Richmond, Virginia

In downtown Richmond, Va., a highly diatomaceous deposit contains a diatom assemblage in which 87 taxa have been identified. The diatoms indicate that this sedimentary unit is correlative with Lithologic Unit 19 of the Choptank Formation of middle Miocene age. Also in Richmond, a sedimentary unit correlated with the Eastover Formation overlies the Choptank Formation and contains a sparse diatom assemblage in which 24 taxa have been identified. The diatoms in this upper deposit form an assemblage that is distinctive from that of the Choptank Formation and is of late Miocene age. Both diatom assemblages are dominated by taxa indicating deposition in a littoral or shallow neritic marine environment. Although reasons for differences in diatom diversity and abundance between the two formations are obscure, these differences appear to reflect the greater primary productivity of diatoms in middle Miocene than in later Tertiary time.