Facies Characteristics of the Cenomanian–Maastrichtian Sequence of the Beydaglari Carbonate Platform,Korkuteli Area,Western Taurides,Turkey

In the Korkuteli area of the western Taurides, Upper Cretaceous sequences consist of the neritic and hemipelagic Beydaglari Formation and the pelagic Akdag Formation. These formations show important facies variations and stratigraphic gaps. The Beydaglari Formation, ranging in age from Cenomanian to Santonian, is approximately 600 m thick, and is composed mainly of platform-type neritic carbonates. Five microfacies indicating tidal-flat, subtidal (lagoonal), reef, and forereef subenvironments are distinguished in the neritic carbonates of the formation. Benthic foraminifera and rudists are the main biological components that provide information about the environment and age of the unit. In addition, cryptalgal lamination also is recognized as an important tool in determining environment. The uppermost part of the Beydaglari Formation is composed of hemipelagic carbonates (a sixth microfacies), which were deposited under basinal conditions. The Akdag Formation consists of planktonic foraminifera-bearing pelagic carbonates, suggesting a Campanian-Maastrichtian age and deposition as a basinal facies. The formation disconformably overlies the Beydaglari Formation along an erosional surface.

Eocene transgressive pelagic clayey carbonates of the Ulucak Formation unconformably overlie the Upper Cretaceous carbonate sequences. Detailed investigations have shown that, at least in the studied part of the autochthonous unit, the platform began to drown during the Santonian and that a true basinal environment persisted from the Campanian to the Maastrichtian. Two erosional phases are recorded; one occurred after the Santonian and is characterized by a prominent erosional surface, and the other is responsible for the post-Cretaceous regression.     

Biostratigraphy and facies analysis of the Upper Cretaceous–Danian? platform carbonate succession in the Kuyucak area,western Central Taurides,S Turkey

The Upper Cretaceous succession outcropping in the Anamas–Akseki Autochton, consists of approximately 500 m thick purely platform carbonate sediments. It begins with Cenomanian limestones intercalated with limestone breccias (Unit-1) containing mainly Pseudorhapydionina dubia, Pseudonummoloculina heimi, Spiroloculina cretacea (Assemblage I) and unconformably overlies the Lower Cretaceous (Barremian–Aptian) limestones with Vercorsella laurentii, Praechrysalidina infracretacea and Salpingoporella hasi. The Cenomanian limestones include foraminiferal packstone–wackestone, peloidal packstone–wackestone and mudstone microfacies deposited in restricted platform conditions. The Cenomanian succession is truncated by an unconformity characterised by locale bauxite deposits. Immediately above the unconformable surface, dolomitic limestones and rudistid limestones (Unit-2) are assigned to the upper Campanian based on the benthic foraminiferal assemblage (Assemblage II) comprising mainly Murciella gr. cuvillieri, Pseudocyclammina sphaeroidea, Accordiella conica, Scandonea samnitica and Fleuryana adriatica (smaller-sized populations). The upper Campanian limestones composed of dominantly foraminiferal-microbial packstone–wackestone microfacies deposited in shallow water environment with low energy, restricted circulation. The following limestones of the Unit-2 is characterised by sporadic intercalation of “open shelf” Orbitoides, Omphalocyclus, Siderolites assemblage (Assemblage III), assigned to the Maastrichtian, in addition to pre-existing “restricted platform” species. In the upper part of this biozone, the Rhapydionina liburnica/Fleuryana adriatica concurrent range subzone (Assemblage IIIb) is distinguished by the presence of Valvulina aff. triangularis, Loftusia minor as well as the nominal species. The Maastrichtian limestones with sporadically open marine influence consist of bioclastic (rudist-bearing) packstone–floatstone, foraminiferal packstone–wackestone with rudist fragments and peloidal/intraclastic packstone–wackestone microfacies deposited in shallow subtidal–subtidal (lagoonal) environments. The Upper Cretaceous succession passes upwardly into 70 m thick limestones and clayey limestones (Unit-3) which do not contain rudists and pre-existing foraminiferal assemblage with one exception Valvulina aff. triangularis. Variable amounts of ostracoda, discorbids, miliolids, dasycladacean algae and Stomatorbina sp. (Assemblage IV) occur into mud-rich microfacies suggesting restricted conditions with low water energy. A probable Danian age is proposed for the Unit-3 based on the occurrence of Valvulina aff. triangularis and Stomatorbina sp. which were previously recorded from Danian of peri-Tethyan platforms.     

Late Cretaceous – Early Tertiary sedimentation and tectonic inversion in the southern Netherlands

Analysis of the Upper Cretaceous stratigraphy of the Peel Block reveals the basin development of the block to have been influenced by both the inversion of the Roer Valley Graben and Central Netherlands Basin, and the overall Late Cretaceous transgression. Sediments of Santonian to Danian age were deposited on the block. These sediments are compared with the detailed lithostratigraphy of southern Limburg, where Late Cretaceous strata are exposed. Four successions can be recognised in southern Limburg. The two oldest successions, the Santonian Oploo Formation (new name, proposed in the present contribution) and the mainly Early Campanian Vaals Formation, are restricted to the central and northern parts of the block. These siliciclastic formations were deposited under the influence of inversion of the Roer Valley Graben and the Central Netherlands Basin, as well as under the influence of a rising sea level. Towards the north, sands of the Oploo Formation grade into marls and chalks of the Ommelanden Formation. The two youngest successions comprise the largely Late Campanian to Maastrichtian Gulpen and Maastricht Formations and the Danian Houthem Formation. These chalk formations were deposited under the influence of regional subsidence during a sea-level highstand. Subsequent to deposition of the Houthem Formation, a regional regression triggered a change from shallow-marine carbonate to paralic siliciclastic deposition.     

Late Santonian–Early Maastrichtian calcareous nannofossils from marly deposits near Kerman (Central Iran)

For the first time, the calcareous nannofossils of marly deposits near Kerman (Bardsir area) have been studied. This study presents the integrated (calcareous nannofossils) biostratigraphy of the Bardsir section in the Kerman basin, Central Iran. In most parts of Central Iran, the Upper Cretaceous sequence is complete and continuous and is divided into two groups: Cenomanian–Touronian flysch and Campanian–Maastrichtian flysch. Flyschs composed of sets of green marl sequences (Coniacian–Santonian) have been separated to reduce the basin depth and refer to the relative calm. Bardsir is located 57.6 km from Kerman (Central Iran). The lithology of this area includes light green marl with layers of calcareous siltstone, limestone, and flysch rocks. In this study, 24 samples were taken and prepared with smear slide. Most species were photographed with a light microscope. As a result of this study, 30 genera and 42 species of nannofossils have been identified. A high-resolution calcareous nannofossil biostratigraphic study has been carried out, allowing the division of the studied section into eight biozones of Late Santonian to Early Maastrichtian age (CC17–CC24).     

Late Cretaceous oceanic crust and Early Tertiary foreland basin development, Euboea, Eastern Greece

In northern Euboea (Eastern Greece), Late Cretaceous platform carbonates of the Pelagonian Zone pass depositionally upwards into Maastrichtian hemipelagic limestones, possibly reflecting a rifting event in the adjacent Neotethys. This is followed by a c. 1 km-thick unit of siliciclastic turbidites, debris flows and detached limestone blocks. Thrust intercalations of ophiolitic rocks comprise altered pillow basalts and ultramafic rocks with ophicalcite. Calcite veins in sheared serpentinite contain planktonic foraminifera and the ophicalcite is directly overlain, with a depositional contact, by Globotruncana-bearing pelagic limestones and calciturbidites of Maastrichtian age. The ophiolitic rocks are interpreted as Late Cretaceous oceanic crust and mantle, that formed at a fracture zone, or rifted spreading axis within a Neotethyan, Vardar basin to the east. During the Early Tertiary (Palaeocene–Eocene), the Neotethyan basin began to close, with development of a subduction-accretion complex, mainly comprising sheared, trench-type sandstones, associated with ophiolitic slices. In response to trench/margin collision, the Pelagonian carbonate platform foundered and limestone debris flows and olistoliths were shed into a siliciclastic foreland basin. Suturing of the Neotethyan ocean basin then resulted in westwards thrusting of oceanic units over the foreland basin, thrusting of slices of inferred Late Cretaceous Pelagonian carbonate platform slope and large-scale recumbent folding.     

The influence of Late Cretaceous synsedimentary deformation on the Cenozoic structuration of the middle Adriatic,Croatia

The primordially structural-lithofacial relationships in the Adriatic Carbonate Platform (AdCP) of Croatia were formed by a Late Cretaceous synsedimentary tectonics. During Cenomanian, an extensional tectonic regime differentiated AdCP into several kilometres large paleoenvironmental segments which behaved as individual depocenteres. The latest Cenomanian and earliest Turonian were tectonically relatively quiet periods during which sediments only recorded a relative sea-level rise. Compression commenced during the middle Santonian and formed first (NW-SE) gentle folds in the frontal part of the Split-Dubrovnik thrust. These folds had amplitudes of tens to hundreds of metres and are up to ten kilometres in strike. The apical parts of the anticlines were dominated by shallow-marine deposition with short emergences simultaneously, slope deposition of pelagic sediments took place in the synclines. By the end of the Campanian, compression weakened and younger sediments infilled former depressions while the deposition ended in the Adriatic hinterland of Croatia. During the Maastrichtian the compression recommenced and the index of older folds increased while new folds and reverse faults were formed. Such deformations created a differentiated morphology at the surface subsequently overlaid by Palaeogene sediments. Clastic sediments accumulated indeed in this paleodepression during the Palaeogene and Miocene–Quaternary, forming favourable structural conditions for hydrocarbon generation.     

Paläogeographische Entwicklungen an mobilen Schollengrenzen im Westhindukusch (Bande Amir,Zentralafghanistan)

In the region of Bande Amir, located on the southern rim of the Tadschik basin, the Mesozoic section starts with detrital and conglomeratic limestones. These marine deposits of Upper Cretaceous age (Cenomanian-Turonian) disconformably cover a truncated complex of Upper Paleozoic rocks (Permian). After an interval of neritic sedimentation (Santonian, Campanian) the Upper Cretaceous sea (Maastrichtian) regressed from the Central Afghanian High. In the Hindukusch mountains the regression is related to crustal movements and regional uplifts, which hinged on the Herat lineament. Intermontane basins, developed on this mobile zone during mid-Tertiary time, gathered continental debris (Neogene conglomerates; Zohak-Formation) and led to the deposition of lacustrine sediments (Ghulghola-Formation). Orogenetic movements along the colliding edges of crustal blocks were rejuvenated in Plio-Pleistocene time, shifting the focus of deposition to the northwest. The basin was finally captured by the Amu Darja drainage system, leading to the development of canyon-like incisions. During warm periods of the Quaternary, fluviatile erosion in Bande Amir was interrupted at least four times by the retention of water behind large dams of travertine.     

Late Cretaceous (Santonian) Atractosteus (Actinopterygii,Lepisosteidae) remains from Hungary (Iharkút,Bakony Mountains)

Lepisosteid fishes are well known from the Upper Cretaceous of Europe, but only by fragmentary remains from some Cenomanian and Campanian–Maastrichtian deposits. Here we report various cranial and postcranial remains of gars, discovered in the Upper Cretaceous (Santonian) Csehbánya Formation of Iharkút (Bakony Mountains, Hungary). These remains represent one of the most diverse assemblages of lepisosteid fish material from Upper Cretaceous continental deposits of Europe. Based on tooth morphology, scale-microstructure and the features of the supracleithrum we refer these remains to the genus Atractosteus. Besides some uncertain remains from the Cenomanian of France and Spain, the Santonian aged fossils from Iharkút represent the oldest undisputable occurrence of the family Lepisosteidae in the European continental Cretaceous. Using tooth crown morphology, the surface microstructure of the ganoid scales and the anatomy of the supracleithrum a review of the Late Cretaceous lepisosteid record suggests the occurrence of both Atractosteus and Lepisosteus in the European archipelago.     

Cretaceous rudist-bearing platform carbonates from the Lycian Nappes (SW Turkey): Rudist associations and depositional setting

Lycian Nappes (in SW Turkey) lie between the Menderes Massif and Bey Dağları carbonates and comprise thrust sheets (nappes piles) of Paleozoic-Cenozoic rocks, ophiolitic and tectonic mélanges and serpentinized peridodites. This study focuses on identification of rudists and their palaeoenvironmental features observed within the Cretaceous low grade metamorphic successions (dominated by recrystallized limestones) from the Tavas and Bodrum nappes. The study is based on fifteen stratigraphic sections measured from Tavas, Fethiye, Köyceğiz, Bodrum, Ören and Bozburun areas. The Lower Cretaceous successions with rudists are very sparse in the Lycian Nappes and a unique locality including a Berriasian epidiceratid-requieniid assemblage is reported so far. A new requieniid-radiolitid assemblage was found within the pre-Turonian (?Albian-?Cenomanian) limestones. Four different Late Cretaceous rudist assemblages were firstly identified as well: 1) Caprinid-Ichthyosarcolitid assemblage (middle-late Cenomanian); 2) Distefanellid assemblage (late Turonian); 3) Hippuritid-Radiolitid assemblage (late Coniacian-Santonian-Campanian); 4) Radiolitid-Hippuritid assemblage (‘middle’-late Maastrichtian). Microfacies data and field observations indicate that the rudists lived in the inner and outer shelves of the Cretaceous carbonate platform(s) in this critical part of the Neotethys Ocean. Rudists formed isolated patchy aggregations in very shallow palaeoenvironments and deposited as shell fragments particularly on the outer shelf environment, which is characterized by higher energy and platform slope characteristics.     

Planktonic foraminiferal biostratigraphy of the Coniacian-Maastrichtian sequences of the Bey Dağları Autochthon,western Taurides,Turkey: thin-section zonation

Planktonic foraminifer distributions in seventeen stratigraphic sections of Upper Cretaceous hemipelagic and pelagic sequences of northern Bey Da?lar? Autochthon (western Taurides) yield six biozones such as, Dicarinella concavata Interval Zone, Dicarinella asymetrica Range Zone, Radotruncana calcarata Range Zone, Globotruncana falsostuarti Partial Range Zone, Gansserina gansseri Interval Zone, and Abathomphalus mayaroensis Concurrent Range Zone. Two of the zones, Dicarinella concavata Zone and Dicarinella asymetrica Zone, are identified in the massive hemipelagic limestones of the Bey Da?lar? Formation, of Coniacian-Santonian age. They are characterized by scarce planktonic foraminifera and abundant calcisphaerulids. The other four biozones are determined from the cherty pelagic limestones of the Akda? Formation and indicate a late Campanian-late Maastrichtian time interval. The planktonic foraminifera observed in these four biozones are diverse, complex morphotypes (K-selection), suggesting open oceans. The assemblage of the Abathomphalus mayaroensis Zone shows that the latest Maastrichtian record is absent throughout the northern part of the autochthon. Two main sedimentary hiatuses are recognized within the Upper Cretaceous pelagic sequence. Early to middle Campanian and latest Maastrichtian-middle Paleocene planktonic foraminifera are absent in all measured stratigraphic sections. Hiatus durations differ between sections as a result of diachronism of onset of the hemipelagic and pelagic deposition and the post-Santonian and post-Maastrichtian erosional phases. Drowning event and the early-middle Campanian and latest Maastrichtian-middle Paleocene hiatuses in the pelagic sequence are attributed to regional tectonics during the Late Cretaceous.     

Formation and emplacement ages of the SSZ‐type Neotethyan ophiolites in Central Anatolia,Turkey: palaeotectonic implications

Isolated outcrops of ophiolitic rocks, termed the Central Anatolian Ophiolites, are found as allochthonous bodies in the Central Anatolian Crystalline Complex, that represent the metamorphosed passive northern edge of the Tauride–Anatolide Platform, central Turkey. In terms of pseudostratigraphic relationships of the magmatic units and their chemical designation, the Central Anatolian Ophiolites exhibit a supra‐subduction zone (fore‐arc) setting within the Vardar–İzmir–Ankara–Erzincan segment of the Neotethys. The epi‐ophiolitic sedimentary cover of the Central Anatolian Ophiolites is generally characterized by epiclastic volcanogenic deep‐sea sediments and debris flows intercalated with pelagic units. The richest and most significant planktonic foraminiferal association recorded from the lowest pelagic members infer a formation age of early–middle Turonian to early Santonian. K/Ar ages of post‐collisional granitoids (81–65 Ma) intruding the basement rocks as well as the Central Anatolian Ophiolites suggest a post‐early Santonian to pre‐middle Campanian emplacement age. The marked high volume of epiclastic volcanogenic sediments intercalated with the pelagics of the Central Anatolian Ophiolite is suggestive of rifting in a marginal sea adjacent to a volcanic arc. Penecontemporaneous tectonism is reflected in repetitions in the stratigraphy and in debris flows, which result from major slides and mass‐gravity reworking of pre‐existing units and of arc‐derived volcanics and sediments. Correlating the rock units and formation/obduction ages of the Central Anatolian Ophiolites with further supra‐subduction zone type ophiolites in the eastern (Turkey) and western (Greece) parts of the Vardar–İzmir–Ankara–Erzincan segment of Neotethys we conclude that the intraoceanic subduction in the east is definitely younger and the closure history of this segment is more complex than previously suggested. Copyright © 2000 John Wiley & Sons, Ltd.     

Basin evolution model during cretaceous in the northeastern of Arabian plate in Kurdistan region

The research area concentrates in a part of the main Zagros fold and thrust belt in the Kurdistan region (Northern Iraq). From study tectono-stratigraphy we constrain the story of the basin evolution of Kurdistan during Cretaceous. However we mainly investigated the evolution of the pre-Subduction and Pre-collision periods, focusing on the relationship between tectonics and sedimentation. For this purposes we developed (1) a biostratigraphic approach using nannofossil analysis, (2) a fault tectonic analysis, and (3) a stratigraphic study. The Zagros fold belt in Kurdistan exhibits many lateral and vertical environmental and facies changes, especially during the Cretaceous times. During the Jurassic period the Kurdistan is occupied by the restricted Gotnia Basin. This basin disappeared and the Kurdistan area changed to open marine of a southwest Kermanshah Basin during the Cretaceous. During the Berriasian to Barremian the Kurdistan was covered by the carbonates of the Balambo and Sarmord formations. In the east and southeast the neritic Sarmord Formation gradationally and laterally passes to the basinal facies of the Balambo Formation. In the Aptian to Cenomanian period shallow massive reefal limestone of the Qamchuqa Formation deposited. The normal faulting that initiates during the Aptian is associated with an abrupt lateral change of the reefal Qamchuqa Formation to the Aptian-Cenomanian part of the Balambo Formation. During the Cenomanian-Early Turonian periods the graben formed in the Dokan Lake in eastern Kurdistan, where developed a deeper restricted environment (Dokan and Gulneri formations) surrounded by a shallow marine platform. During the Turonian the marine pelagic micritic cherty limestones of Kometan Formation covered northeast of Kurdistan, whereas in the Safeen, Shakrok and Harir anticlines the formation was totally, or partially, weathered during the Coniacian-Early Campanian period. The deposition during the Late Cretaceous is very heterogeneous with a gap in the Coniacian-Santonian times probably related to a non-deposition. Associated with extensive tectonics a basin developed during the Campanian with the deposition of shales, marls and marly limestones of the Shiranish Formation. The first appearance is the Kurdistan of the flysch facies of the Tanjero Formation was precisely dated of the Upper Campanian in northeastern Kurdistan. The Tanjero Formation conformably overlaying the Shiranish Formation and was deposited in the foredeep basin associated with the obduction of Tethyan ophiolites onto the Arabian Platform. The Early to Late Campanian period is a time of non-deposition in Central Kurdistan (Safeen, Shakrok and Harir anticlines). During the Late Campanian the Bekhme carbonate platform in the north disappeared when the marly limestones of the Shiranish Formation transgressed over the Bekmeh Platform. In the Aqra area the Maastrichtian Tanjero Formation laterally changed to the thick reefal sequence of the Aqra Formation that unconformably overlies by the Late Paleocene-Early Eocene lagoonal carbonate of the Khurmala Formation. The Campanian sedimentation is mainly controlled by NE- oriented normal faults forming Grabens in Dokan, Spilk and Soran areas. During the Maastrichtian in the extreme northeastern Kurdistan the NE-SW and NNW-SSE normal faults developed in the foredeep basin and originated horsts and grabens.     

Palynostratigraphy and palaeoenvironmental significance of the Cretaceous palynomorphs in the Qattara Rim-1X well,North Western Desert,Egypt

Palynological and palynofacies analyses were carried out on some Cretaceous samples from the Qattara Rim-1X borehole, north Western Desert, Egypt. The recorded palynoflora enabled the recognition of two informal miospore biozones arranged from oldest to youngest as Elaterosporites klaszii-Afropollis jardinus Assemblage Zone (mid Albian) and Elaterocolpites castelainii–Afropollis kahramanensis Assemblage Zone (late Albian–mid Cenomanian). A poorly fossiliferous but however, datable interval (late Cenomanian–Turonian to ?Campanian–Maastrichtian) representing the uppermost part of the studied section was also recorded. The palynofacies and visual thermal maturation analyses indicate a mature terrestrially derived organic matter (kerogen III) dominates the sediments of the Kharita and Bahariya formations and thus these two formations comprise potential mature gas source rocks. The sediments of the Abu Roash Formation are mostly dominated by mature amorphous organic matter (kerogen II) and the formation is regarded as a potential mature oil source rock in the well. The palynomorphs and palynofacies analyses suggest deposition of the clastics of the Kharita and Bahariya formations (middle Albian and upper Albian–middle Cenomanian) in a marginal marine setting under dysoxic–anoxic conditions. By contrast, the mixed clastic-carbonate sediments of the Abu Roash Formation (upper Cenomanian–Turonian) and the carbonates of the Khoman Formation (?Campanian–Maastrichtian) were mainly deposited in an inner shallow marine setting under prevailing suboxic–anoxic conditions as a result of the late Cenomanian and the Campanian marine transgressions. This environmental change from marginal to open (inner shelf) basins reflects the vertical change in the type of the organic matter and its corresponding hydrocarbon-prone types. A regional warm and semi-arid climate but with a local humid condition developed near/at the site of the well is thought to have prevailed.     

藏南江孜县床得剖面侏罗-白垩纪地层层序及地层划分

重测西藏南部江孜床得剖面后发现地层层序与前人认识完全相反,不只含上白垩统,还包括中—上侏罗统和整个白垩系;重新厘定了宗卓组、加不拉组,新建床得组,它们分属晚坎潘期—马斯特里赫特期、贝里阿斯期—三冬期和早—中坎潘期;由下向上可识别出６套沉积组合：安山岩层、黄层、黑层、白层、红层及滑塌层,大致对应于下热组（Ｊ２ｘ ）、维美组（Ｊ３ｗ ）、加不拉组（Ｋ（１－ ２）ｊ,床得浦段＋ 机布里段）、床得组（Ｋ２ｃ）、宗卓组（Ｋ２ｚｎ）     

Stratigraphy and radiolarians of upper cretaceous sedimentary cover of the Arakapas ophiolite massif (Cyprus)

In the basal interval, sedimentary cover of the Arakapas ophiolite massif (southern Cyprus) is composed of metalliferous sediments of the Perapedhi Formation that is divided into three sequences based on diverse radiolarian assemblages. These are basal umbers of the Cenomanian age presumably (2–20 m), interlayering cherts and umbers of the Turonian-Coniacian (6–10 m), and opoka-like cherts of the Coniacian-Santonian. Higher in the succession, there are olistostrome deposits of the Moni Formation, which unconformably rest on the eroded underlying strata. In this formation also divisible into three sequences, the lower one 200 to 300 m thick is composed of variegated, presumably Campanian silty clays containing olistoliths of basic, presumably Upper Triassic volcanics, Lower Cretaceous sandstones, and opoka-like cherts and cherty limestones of the Albian-lower Cenomanian. Next sequence (100–200 m) is represented by alternation of variegated silty and green bentonitic clays of the Campaian, which enclose frequent olistoliths and horizons of fine-clastic olistostrome breccias. The upper sequence of upper Campanian-lower Maastrichtian bentonitic clays (50–100 m) contains interlayers of ash tuffs and clayey cherty sediments. Carbonate deposits of the upper Maastrichtian-Paleogene, conformably overlie the Moni Formation.     

Alter und Genese des Nicoya-Komplexes,einer ozeanischen Paläokruste (Oberjura bis Eozän) im südlichen Zentralamerika

The Nicoya Complex, built by thick sequences of mainly oceanic basalts and exposed on the numerous pacific peninsulas of Costa Rica and Panama (Fig. 1), is, for the first time, divided by means of biostratigraphic and facies methods. This classification is not only possible by means of biostratigraphic dating of the overlying sediments but also of occasional inclusions of sedimentary silicious and calcareous exotic blocks within the basaltic sequences. This method shows that the formation of the Nicoya Complex, contrary to the hitherto idea of a uniphase and short development, not only took up very long periods of geological time but was also very discontinuously built. The Nicoya Complex can now be divided into six subcomplexes of different age which, in part, may already be regionally differentiated (Fig. 33). These subcomplexes have to be interpreted as being submarine, abyssal to bathyal sheet flows of mainly tholeiitic basalts up to several hundred meters in thickness. During these effusions of short time duration, the sedimentary cover, in the meantime deposited on the underlying effusiva, was more or less intensively reworked by these processes and deported within the new effusion body in form of exotic blocks (xenolithes, volcanic mélange) where contactmetamorphic changes partly occurred. The following subcomplexes, named after their type localities, are differentiated:

1. The subcomplex of Brasilito contains radiolarite-, respectively jaspilite-xenolithes (contactmetamorphosis!) of early Lower Cretaceous and especially Upper Jurassic. TheSphaerostylus lanceola- zone is proved by rich radiolarian faunas. In these radiolarites, developed below the CCD, partly workable manganese nodule deposits are occurring. Hitherto these were explained as being hydrothermal replacements of basic volcanites and sediments (Webber 1942,Roberts 1944) now compared with similar occurrences in the Olympic Peninsula (Roy 1976).
2. Because the xenolithes of the subcomplex of Junquillal have suffered stronger contactmetamorphosis, their biostratigraphic classification is not entirely proved.
3. The subcomplex of Murcielago on the Nicoya peninsula is widespread. Xenolithes, so far, were less useful here. But this subcomplex possesses well-developed sedimentary overlying units which are not noticed in the older ones. They start with radiolarian rocks of the older Campanian and succeed with pelagic limestones during the Upper Campanian, followed by mostly thick tuffitic sediments.
4. The subcomplex of Golfito contains numerous xenolithes from silicious limestones of the Upper Campanian in which, besides planktonic foraminifers, well-preserved radiolarians are met.
5. The subcomplex of Garza contains xenolithes of pelagic limestones rich of faunas of the Middle Maastrichtian planktonic foraminifers and is superposed by pelagic limestone of the uppermost Maastrichtian.
6. The subcomplex of Quepos contains xenolithes of Paleocene age (planktonic foraminifers and macro-foraminifers), partly developed as classical mélange in the sense of HSÜ, and is overlain by sediments of the Lower Eocene.

Consequently, the age of these volcanic occurrences can be classified biostratigraphically as follows: Late Lower Cretaceous (1); post-Cenomanian but pre-Campanian (2); about Santonian or Lowest Campanian (3); post-Campanian, probably at the beginning of the Maastrichtian (4); Upper Maastrichtian (5) and presumably boundary of Paleocene/Eocene (6). As these subcomplexes represent abyssal to bathyal volcanic lava sheets — adjoining and younger plutonic intrusions have to be neglected — they cannot be interpreted as being a primary oceanic crust built on a mid-oceanic ridge. Therefore, it can be assumed that such rocks are present in the underlying basal part of the older effusion bodies. In fact, pyrite deposits of massive layer-bounded sulphides, typical for the top of such ophiolithic sequences, are occurring in pillow basalts near Punta Gorda below the Brasilito subcomplex as far as can be geologically recognized (E.Kuypers 1977: personal communication). Using these and further data, the geotectonical development may be reconstructed (Fig. 34). An aseismic rise “Nicoya-Azuero” which “far away” in the Pacific is still developing since the end of the Jurassic (the palaeomagnetic test is still outstanding) and, since the formation of a subduction zone in the southern part of Central America, is moving into the direction of this zone — there is biostratigraphic proof of an island arc “Nicaragua-Panama” from about the Cenomanian onwards. In the Campanian, at least parts of this “Nicoya-Azuero rise” possess an authentic submarine relief of more than 4 km. Finally, during the Campanian, this rise slowly comes into contact with the subduction zone: Removing of the subduction to the E takes place [in the sense ofVogt et al. (1976)] leading to a plugging of the subduction zone by drifting of rise sections (cf. with the present geotectonical relation between the Cocos/Coiba rise and the Central American isthmus); and finally, during this course of movements, there is an advancing echelon shearing by parts of the rise into a lateral direction and an attachment to the island arc (cf.Lowrie 1978). During this time strong vertical movements also occur which, at times, lead to a considerable isostatic uplift of the southern Central America - (faunal exchange of short duration from N to S America! - cf. present situation). After the last oceanic effusions at the boundary Paleocene/Eocene, this development is finally completed during the Eocene, whilst the Central American subduction zone has finally shifted W in front of the “ruins” of the previous “Nicoya-Azuero rise” (plate boundary jumping). Since the Upper Eocene the Nicoya Complex tectonically shows platform characteristics and is continentally orientated.     

Cretaceous Oceanic Red Beds: Distribution, Lithostratigraphy and Paleoenvironments

Cretaceous oceanic red beds (CORBs) represented by red shales and marls, were deposited during the Cretaceous and early Paleocene, predominantly in the Tethyan realm, in lower slope and abyssal basin environments. Detailed studies of CORBs are rare; therefore, we compiled CORBs data from deep sea ocean drilling cores and outcrops of Cretaceous rocks subaerially exposed in southern Europe, northwestern Germany, Asia and New Zealand. In the Tethyan realm, CORBs mainly consist of reddish or pink shales, limestones and marlstones. By contrast, marlstones and chalks are rare in deep-ocean drilling cores. Upper Cretaceous marine sediments in cores from the Atlantic Ocean are predominantly various shades of brown, reddish brown, yellowish brown and pale brown in color. A few red, pink, yellow and orange Cretaceous sediments are also present. The commonest age of CORBs is early Campanian to Maastrichtian, with the onset mostly of oxic deposition often after Oceanic Anoxic Events (OAEs), during the early Aptian, late Albian-early Turonian and Campanian. This suggests an indicated and previously not recognized relationship between OAEs, black shales deposition and CORBs. CORBs even though globally distributed, are most common in the North Atlantic and Tethyan realms, in low to mid latitudes of the northern hemisphere; in the South Atlantic and Indian Ocean in the mid to high latitudes of the southern hemisphere; and are less frequent in the central Pacific Ocean. Their widespread occurrence during the late Cretaceous might have been the result of establishing a connection for deep oceanic current circulation between the Pacific and the evolving connection between South and North Atlantic and changes in oceanic basins ventilation.     

Dinosaur eggshells from the Santonian Milk River Formation of Alberta,Canada

The North American fossil record of dinosaur eggshells for the Cretaceous is primarily restricted to formations of the middle (Albian–Cenomanian) and uppermost (Campanian–Maastrichtian) stages, with a large gap in the record for intermediate stages. Here we describe a dinosaur eggshell assemblage from a formation that represents an intermediate and poorly fossiliferous stage of the Upper Cretaceous, the Santonian Milk River Formation of southern Alberta, Canada. The Milk River eggshell assemblage contains five eggshell taxa: Continuoolithus, Porituberoolithus, Prismatoolithus, Spheroolithus, and Triprismatoolithus. These ootaxa are most similar to those reported from younger Campanian–Maastrichtian formations of the northern Western Interior than they are to ootaxa reported from older middle Cretaceous formations (i.e., predominantly Macroelongatoolithus). Characteristics of the Milk River ootaxa indicate that they are ascribable to at least one ornithopod and four small theropod species. The taxonomic affinity of the eggshell assemblage is consistent with the dinosaur fauna known based on isolated teeth and fragmentary skeletal remains from the formation, although most ornithischians and large theropods are not represented by eggshell. Relative to the Milk River Formation eggshell, similar oospecies occurring in younger Cretaceous deposits tend to be somewhat thicker, which may reflect an increase in body size of various dinosaur lineages during the Late Cretaceous.     

Stratigraphy of the upper cretaceous and lower tertiary strata in the Tethyan Himalayas of Tibet (Tingri area,China)

The 1500-m-thick marine strata of the Tethys Himalaya of the Zhepure Mountain (Tingri, Tibet) comprise the Upper Albian to Eocene and represent the sedimentary development of the passive northern continental margin of the Indian plate. Investigations of foraminifera have led to a detailed biozonation which is compared with the west Tethyan record. Five stratigraphic units can be distinguished: The Gamba group (Upper Albian - Lower Santonian) represents the development from a basin and slope to an outer-shelf environment. In the following Zhepure Shanbei formation (Lower Santonian - Middle Maastrichtian), outer-shelf deposits continue. Pebbles in the top layers point to beginning redeposition on a continental slope. Intensified redeposition continues within the Zhepure Shanpo formation (Middle Maastrichtian - Lower Paleocene). The series is capped by sandstones of the Jidula formation (Danian) deposited from a seaward prograding delta plain. The overall succession of these units represents a sea-level high at the Cenomanian/Turonian boundary followed, from the Turonian to Danian, by an overall shallowing-upward megasequence. This is followed by a final transgression — regression cycle during the Paleocene and Eocene, documented in the Zhepure Shan formation (?Upper Danian - Lutetian) and by Upper Eocene continental deposits. The section represents the narrowing and closure of the Tethys as a result of the convergence between northward-drifting India and Eurasia. The plate collision started in the Lower Maastrichtian and caused rapid changes in sedimentation patterns affected by tectonic subsidence and uplift. Stronger subsidence and deposition took place from the Middle Maastrichtian to the Lower Paleocene. The final closure of remnant Tethys in the Tingri area took place in the Lutetian.     

Upper cretaceous biostratigraphy of the south-central Pyrenees (Lleida,Spain)

Abstract

Biostratigraphical data using larger foraminifera and planktonic foraminifera permitted us to establish the correlation between shallow platform sediments rich in larger foraminifera (Montsec and Serres Marginals thrust sheets) and deeper ones containing planktonic foraminifera (Boixols thrust sheet).

Consequently, the Santa Fe limestones containing Ovalveolina-Praealveolinaassemblage represent the Cenomanian. Early Turonian ( ‘IT~ archaeocretacea and P. helvetica zones) exist in both, Montsec and Boixols thrust sheets and it is constituted by Pithonella limestones. Late Turonian (M. schneegansi zone) is only present in Boixols thrust sheet (Reguard Fm.), the Montsec thrust sheet having an erosive hiatus.

Late Coniacian-Early Santonian (D. Concavata zone) is represented in the Montsec thrust sheet (Cova Limestones) and in the eastern part of the Boixols thrust sheet (St. Corneli Fm.) by two differents facies giving two different microfaunal assemblages; the firts one, characterized by Ophtalmidiidae s.l indicate a restricted lagoonal environment while the second one, characterized by diverses species of complex agglutinated, Fabulariidae, Meandropsinidae and Rotaliidae, represents an open shallow platform. In the Boixols thrust sheet (Anseroles Fm.) dominate the planktonic foraminifera and small benthic.

In the late Santonian (D. asyrnetrica zone) the sea reached as far as Serres Marginales thrust sheet where sediments (Tragó de Noguera unit) are terrigenous and deposited in a very shallow platform. In the Montsec thrust sheet (Montsec marls) the larger foraminifera indicate a platform deeper than that of the Serres Marginals thrust sheet. In the Boixols thrust sheet the sediments are deposited in an outer platform (Herbasavina Fm.) or turbiditic basin (Mascarell Mb.).

During Campanian times the transgresion reaches the maximum. In the Serres Marginals sediments are deposited in a restricted shallow environment rich in Meandropsinidae (Serres Limestones). In the Montsec thrust sheet they are deposited in a platform with patch reefs and shoals (Terradets limestones) and in the Boixols one in an outer platform, talus and/or basin.

During Early Maastrichtian times (C. falsostuarti zone) terrigenous materials arrived in the basin, the rate of sedimentation increased outstripping the subsidence rate and the retreat of the sea to the north. Late Maastrichtian (C. gansseri zone) is only present in the Boixols thrust sheet.