Cenomanian Santonian Research Articles

Cretaceous soft-shelled turtles (Trionychidae) of Mongolia: new diversity, records and a revision

This paper is devoted to the description and revision of material of Cretaceous soft-shelled turtles (Trionychidae) of Mongolia. It includes the description of seven trionychid species, six of which are new, and two new genera: the cyclanorbine Nemegtemys conflata gen. et sp. nov. from the Nemegt Formation (Maastrichtian), and the trionychines Gobiapalone breviplastra gen. et sp. nov. from the Nemegt and Barungoyot (Campanian) formations, G. orlovi from the Baynshire Formation (Cenomanian–Santonian), ‘Trionyx’ baynshirensis sp. nov. from the Baynshire Formation, ‘T.’ gilbentuensis sp. nov. from the Nemegt Formation, ‘T.’ gobiensis sp. nov. from the Nemegt Formation, and ‘T.’ shiluutulensis sp. nov. from an unknown formation (Campanian). In addition, one shell from the ?Baynshire Formation of Khermin Tsav is assigned to Gobiapalone sp. The type material of Amyda menneri is considered to be Trionychidae indet. and Amyda menneri to be a nomen dubium. Finally, we revise other available materials of Cretaceous trionychids from 45 localities in Mongolia. Nemegtemys conflata, if correctly assigned, is the earliest known member of Cyclanorbinae. The two species of the new genus Gobiapalone are included in two phylogenetic analyses of Trionychidae. In both analyses Gobiapalone is monophyletic. In the first analysis, Gobiapalone is placed within Apalonina. In the second analysis, Gobiapalone is sister to Apalonina. Thus, the results of both analyses show that Apalonina, which is a rather advanced and well-supported trionychid clade, or its closest sister taxon (stem-Apalonina), were present in the Late Cretaceous of Asia. These results suggest that most other supra-generic clades of modern trionychids had been established in Asia by the Late Cretaceous. That suggestion is supported by the discovery of a cyclanorbine Nemegtemys conflata in the Late Cretaceous of Mongolia. Finally we summarize the latest data on temporal and geographical distributions of Cretaceous Trionychidae of Asia and North America.http://zoobank.org/urn:lsid:zoobank.org:pub:921DA1C5-C4B2-463D-A49D-608024C6036A

The tectonic development of the Northern Adriatic region constrained by Jurassic and Cretaceous paleomagnetic results

In the Northern Adriatic region, there is a clear boundary between the weakly deformed stable core of the Adriatic microplate and its tectonically complicated NE margin, the External Dinarides which are further subdivided on stratigraphic and structural grounds. Although most authors distinguish an Adriatic and a Dinaridic realm within the External Dinarides, the relationship and the present boundary between the realms are matters of discussion. The aim of this study was to obtain paleomagnetic directions from different parts of the Northern Adriatic segment of the External Dinarides and discuss their bearing on the different types of the tectonic models. For this purpose we carried out standard paleomagnetic measurements on biostratigraphically well-controlled samples from 28 localities from the Adriatic mainland and the Northern Adriatic islands and from one Middle Jurassic locality representing the stable core of the Adriatic microplate. In addition, six localities from the Northern Adriatic islands, earlier studied paleomagnetically, were biostratigraphically updated and thus included in the data set. For the Northern Adriatic islands an Albian ( D/ I = 333°/48°, k = 44, α 95 = 9°) and a Cenomanian–Santonian ( D/ I = 334°/46°, k = 188, α 95 = 5°) paleomagnetic direction was defined. They are in perfect agreement with coeval paleomagnetic directions from stable Adria. Thus, the paleomagnetic data clearly support the models which conceive the area as the imbricated margin of the Adriatic microplate. The Early ( D/ I = 338°/49°, k = 118, α 95 = 11°), the Middle ( D/ I = 342°/54°, k = 112, α 95 = 7°) and the Late ( D/ I = 336°/42°, k = 62, α 95 = 16°) Jurassic paleomagnetic directions, all representing the tectonic units of the Adriatic mainland, suggest an about 30° CW rotation of this belt of the External Dinarides with respect to stable Adria. The difference can be interpreted as inherited from the differencial rotations of two independent carbonate platforms, an Adriatic and a Dinaric. Alternatively, thrusting of the more internal belt of the External Dinarides above the Adriaticum may be responsible for the difference.

Carbon isotope fluctuations of terrestrial organic matter for the Upper Cretaceous (Cenomanian–Santonian) in the Obira area of Hokkaido, Japan

AbstractStratigraphic fluctuations of carbon isotope values of terrestrial organic matter within the Upper Cretaceous (Cenomanian–Santonian) sequence in the Obira area of Hokkaido, Japan, record distinctive δ13C fluctuations for the Cenomanian–Turonian boundary, the Middle Turonian, the upper Turonian–lower Coniacian, and the Santonian. A biostratigraphic framework of the age-diagnostic taxa (ammonoids, bivalves and planktic foraminifers) indicates that these δ13C fluctuation events are comparable with those recorded in δ13C data of terrestrial organic matter in Japan and marine carbonates in Europe. These correlations reinforce the utility of these δ13C events in terms of global chemostratigraphy. In particular, the δ13C patterns within the overall positive interval of the Cenomanian–Turonian boundary event are highly conformable between marine and terrestrial records. The consistent nature of these different records of δ13C fluctuation patterns demonstrates that the terrestrial organic δ13C data mirror the global-scale δ13C patterns in the carbon reservoir of ocean–atmosphere–terrestrial biosphere during the Cenomanian–Turonian boundary event. In addition, global correlation of short-term marine and terrestrial organic δ13C fluctuations of the Upper Cretaceous sequence indicate that the magnitude of several terrestrial organic δ13C events appears more amplified than that of coeval marine carbonate δ13C events. This correlation is interpreted to mean that the effects of local CO2 emission into the atmosphere by release of terrestrial methane hydrate or biomass burning of terrestrial vegetation in the hinterland of the NE Asian region have been superimposed on the global δ13C trend and resulted in the terrestrial organic δ13C records of the Yezo Group.

Origins and maturity of organic matter in mid-Cretaceous black shales from ODP Site 1138 on the Kerguelen Plateau

We have conducted elemental, isotopic, and Rock-Eval analyses of Cenomanian–Santonian sediment samples from ODP Site 1138 in the southern Indian Ocean to assess the origin and thermal maturity of organic matter in mid-Cretaceous black shales found at this high-latitude location. Total organic carbon (TOC) concentrations range between 1 and 20 wt% in black to medium-gray sediments deposited around the Cenomanian–Turonian boundary. Results of Rock-Eval pyrolysis indicate that the organic matter is algal Type II material that has experienced modest alteration. Important contributions of nitrogen-fixing bacteria to the amplified production of organic matter implied by the high TOC concentrations is recorded in δ 15N values between −5 and 1‰, and the existence of a near-surface intensified oxygen minimum zone that favored organic carbon preservation is implied by TOC/TN ratios between 20 and 40. In contrast to the marine nature of the organic matter in the Cenomanian–Turonian boundary section, deeper sediments at Site 1138 contain evidence of contributions land-derived organic matter that implies the former presence of forests on the Kerguelen Plateau until the earliest Cenomanian.

Upper Cretaceous stratigraphy of the Gebel Somar area, north-central Sinai, Egypt

The Upper Cretaceous sequence (446 m thick) exposed at Gebel Somar (north-central Sinai) is subdivided, from base to top, into the Raha (upper Cenomanian), Abu Qada (upper Cenomanian–lower Turonian), Buttum (middle Turonian), Wata (middle–upper Turonian), Matulla (Coniacian–Santonian), and Sudr Chalk (lower–upper Maastrichtian) Formations. Foraminifera (mainly planktonic) were used to assign ages to these. Vertical variations in the bio- and lithofacies for the Cenomanian–Santonian succession reflect global changes of sea level. During the late Santonian, the area studied was uplifted in association with the generation of the Syrian arc system. This was accompanied by non-deposition of Campanian sediments. The Maastrichtian Sudr Chalk was laid down in the basin or depocenter generated as a result of the Syrian arc system.

Coniacian ammonites from James Ross Island, Antarctica

The Cenomanian–Santonian biostratigraphy of the James Ross Basin, north-eastern Antarctic Peninsula is in need of comprehensive revision. This is being achieved by the systematic re-investigation of a series of key reference sections on the north-west coast of James Ross Island, with the first of these being located in the vicinity of Brandy Bay. A new suite of 10 ammonite taxa from the uppermost Whisky Bay and Hidden Lake Formations at this locality has overwhelming Coniacian age affinities. It comprises representatives from the Tetragonitidae and Gaudryceratidae, together with the stratigraphically earliest representative of the Kossmaticeratidae and the three earliest Pachydiscidae species from the James Ross Basin. Some fragmentary specimens are assigned to the Collignoniceratidae, and various heteromorphs to the Nostoceratidae, Diplomoceratidae and Baculitidae. The one new taxon described herein is Gaudryceras ( Gaudryceras) strictum sp. nov. This ammonite fauna represents an important precursor to the much more prolific assemblages that occur in the overlying Santa Marta and López de Bertodano formations (latest Coniacian–Maastrichtian). It shows some affinities to the Madagascan Coniacian ammonite fauna, and offers an opportunity for strengthening Late Cretaceous biostratigraphic correlations between the northern and southern hemispheres.

Origins and accumulation of organic matter in expanded Albian to Santonian black shale sequences on the Demerara Rise, South American margin

Ocean Drilling Program Leg 207 recovered thick sequences of Albian to Santonian organic-carbon-rich claystones at five drill-sites on the Demerara Rise in the western equatorial Atlantic Ocean. Dark-colored, finely laminated, Cenomanian–Santonian black shale sequences contain between 2% and 15% organic carbon and encompass Oceanic Anoxic Events 2 and 3. High Rock-Eval hydrogen indices signify that the bulk of the organic matter in these sequences is marine in origin. However, δ 13C org values lie mostly between −30‰ and −27‰, and TOC/TN ratios range from 15 to 42, which both mimic the source signatures of modern C 3 land plants. The contradictions in organic matter source indicators provide important implications about the depositional conditions leading to the black shale accumulations. The low δ 13C org values, which are actually common in mid-Cretaceous marine organic matter, are consequences of the greenhouse climate prevailing at that time and an associated accelerated hydrologic cycle. The elevated C/N ratios, which are also typical of black shales, indicate depressed organic matter degradation associated with low-oxygen conditions in the water column that favored preservation of carbon-rich forms of marine organic matter over nitrogen-rich components. Underlying the laminated Cenomanian–Santonian sequences are homogeneous, dark-colored, lower to middle Albian siltstones that contain between 0.2% and 9% organic carbon. The organic matter in these rocks is mostly marine in origin, but it occasionally includes large proportions of land-derived material.

Secular variation in Late Cretaceous carbon isotopes: a new δ13C carbonate reference curve for the Cenomanian–Campanian (99.6–70.6 Ma)

Carbon stable-isotope variation through the Cenomanian–Santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven Chalk successions in England. The sections show consistent stratigraphic trends and δ13C values that provide a basis for high-resolution correlation. Positive and negative δ13C excursions and inflection points on the isotope profiles are used to define 72 isotope events. Key markers are provided by positive δ13C excursions of up to +2‰: the Albian/Cenomanian Boundary Event; Mid-Cenomanian Event I; the Cenomanian/Turonian Boundary Event; the Bridgewick, Hitch Wood and Navigation events of Late Turonian age; and the Santonian/Campanian Boundary Event. Isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons. An age-calibrated composite δ13C reference curve and an isotope event stratigraphy are constructed using data from the English Chalk. The isotope stratigraphy is applied to successions in Germany, France, Spain and Italy. Correlation with pelagic sections at Gubbio, central Italy, demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the Cenomanian–Turonian stages, confirming established relationships between Tethyan planktonic foraminiferal and Boreal macrofossil biozonations. Correlation of the Coniacian–Santonian stages is less clear cut: magnetostratigraphic evidence for placing the base of Chron 33r near the base of the Upper Santonian is in good agreement with the carbon-iso-tope correlation, but generates significant anomalies regarding the placement of the Santonian and Campanian stage boundaries with respect to Tethyan planktonic foraminiferal and nannofossil zones. Isotope stratigraphy offers a more reliable criterion for detailed correlation of Cenomanian–Santonian strata than biostratigraphy. With the addition of Campanian δ13C data from one of the English sections, a composite Cenomanian–Campanian age-calibrated reference curve is presented that can be utilized in future chemostratigraphic studies.The Cenomanian–Campanian carbon-isotope curve is remarkably similar in shape to supposedly eustatic sea-level curves: increasing δ13C values accompanying sea-level rise associated with transgression, and falling δ13C values characterizing sea-level fall and regression. The correlation between carbon isotopes and sea-level is explained by variations in epicontinental sea area affecting organic-matter burial fluxes: increasing shallow sea-floor area and increased accommodation space accompanying sea-level rise allowed more efficient burial of marine organic matter, with the preferential removal of 12C from the marine carbon reservoir. During sea-level fall, reduced seafloor area, marine erosion of previously deposited sediments, and exposure of basin margins led to reduced organic-carbon burial fluxes and oxidation of previously deposited organic matter, causing falling δ13C values. Additionally, drowning of carbonate platforms during periods of rapid sea-level rise may have reduced the global inorganic relative to the organic carbon flux, further enhancing δ13C values, while renewed platform growth during late transgressions and highstands prompted increased carbonate deposition. Variations in nutrient supply, changing rates of oceanic turnover, and the sequestration or liberation of methane from gas hydrates may also have played a role in controlling carbon-isotope ratios.

Clay mineralogy of the Cretaceous strata of the British Isles

AbstractThe clay mineralogy of the Cretaceous strata of the British Isles is described and discussed within its lithostratigraphical and biostratigraphical framework using published and unpublished sources as well as 1400 new clay mineral analyses. The regional clay mineral variation is described systematically for the following strata:(1)Southern England — Purbeck Limestone Group (Berriasian/Ryazanian; Lulworth and Durlston formations), Wealden Group (Valanginian—Barremian/Aptian; Ashdown, Wadhurst Clay, Tunbridge Wells Sands, Grinstead Clay Member, Wealden Clay, Wessex and Vectis formations), Lower Greensand (Aptian—Lower Albian; Atherfield Clay, Hythe, Sandgate, Folkestone Sands, Ferruginous Sands, Woburn Sands and Faringdon Sponge Gravels formations), Selborne Group (Middle—Upper Albian; Gault Clay and Upper Greensand formations) and the Chalk Group (Cenomanian—Lower Maastrichtian).(2)Eastern England — Cromer Knoll Group (Ryazanian—Upper Albian; Speeton Clay, Spilsby Sandstone, Sandringham Sands, Claxby Ironstone, Tealby, Roach Ironstone, Dersingham, Carstone and Red Chalk (or Hunstanton Red Limestone) formations).(3)Scotland — Inner Hebrides Group (Cenomanian—Campanian; Morvern Greensand, Gribun Chalk, Coire Riabhach Phosphatic Hibernian Greensands formations).(4)Northern Ireland — Hibernian Greensands (Cenomanian—Santonian) and Ulster White Limestone formations (Santonian—Lower Maastrichtian).The stratigraphical patterns of clay mineral variation divide naturally into two types; firstly, the more complex pattern of the Lower Cretaceous strata and secondly, the simple pattern of the Upper Cretaceous. Clay mineral variations in the non-marine and marine Lower Cretaceous strata of England are best explained by the interplay of two main clay mineral assemblages between which all gradations occur. The assemblage which dominates the main clay formations consists of mica, kaolin and poorly defined mixed-layer smectite-mica-vermiculite minerals, and sometimes includes vermiculite and traces of chlorite. It is dominantly of detrital origin and detailed evidence indicates it is derived largely from the reworking of Mesozoic sediments although ultimately from weathered Palaeozoic sediments and metasediments. Although mainly of detrital origin, this assemblage contains a persistent component that formed coevally with the approximate depositional age of its host sediment. Whether this component is of soil origin or was neoformed in the sediment shortly after deposition is unclear. There is little firm evidence indicating the sources of this clay mineral detritus. However, in the strata of the Wealden Group of southern England, mineral trends suggest three sources; one of these was to the west (Cornubian Massif), another must have been the Anglo- Brabant landmass. In the Selborne Group (Middle—Upper Albian) and in the overlying Lower Chalk (Cenomanian) where this assemblage makes its last appearance in the Cretaceous of England, there is good evidence of easterly and south-easterly sources.The second main assemblage tends to be largely monominerallic, and usually dominated by smectite with or without small amounts of mica; less frequently, kaolin, berthierine or glauconite sensu lato is the sole or dominant component. It is considered to be of volcanogenic origin, derived from the argillization of volcanic ash under different conditions of deposition and diagenesis. The source of the ash in Berriasian—Aptian times seems to have been an extensive volcanic field in the southern part of the North Sea and in the Netherlands, whereas in the Albian (and extending into the Cenomanian) a westerly source dominated. The current controversy about the role of climate or pattern of volcanic activity controlling the clay mineral stratigraphy of the Lower Cretaceous is reviewed.In the lower part of the Upper Cretaceous strata of England, Scotland and Ireland, sand-grade glauconite is particularly abundant. Much of it represents the glauconitization of pene- contemporanous volcanic ash, possibly of basaltic origin, associated with continental breakup and the opening up of the Atlantic Ocean and the earliest stages in the development of the Hebridean Tertiary Igneous Province. The Upper Cretaceous Chalk facies of England and Ireland is dominated by a smectite-rich clay assemblage containing mica, and the various hypotheses for its origin (detrital, neoformation, volcanogenic) are reviewed in the light of available mineralogical, chemical and geological data.

The first plesiosaur from the Primorye krai

Riabinin, 1915 wasfound by N.N. Tikhonovich in 1909 in the LowerSenonian (Coniacian–Santonian, 89–83 Ma) of Sakha-lin [3, 4]. This specimen is impossible to identify moreclosely than Plesiosauria indet. [1]. The teeth and ver-tebrae of the long-necked plesiosaurs Elasmosauridaewere found by L.A. Nessov in 1988 in the upper strataof the Koryak Formation (Upper Maastrichtian, 68–65 Ma) on the Pacific coast of the Chukotka Peninsula[4]. In the areas bordering on Russia (Korea, China, andJapan), plesiosaurs have not been recorded. In 2000,V.K. Popov discovered the fourth plesiosaur occurrencein the Far East; it was found during the geological sur-vey in southern Primorye in marine deposits of theKangauz Formation of the Upper Albian (103–98 Ma)on the right slope of the Sukhodol River (Kangauz),opposite the village of Novonezhino ( 43°12 ′ N, 132°35 ′ E), Primorye krai (Fig. 1). This is a caudal ver-tebra of a plesiosaur (specimen ZIN PH, no. 1/48, Pale-oherpetological collection of the Zoological Institute ofthe Russian Academy of Sciences). The bone beds arecomposed of dark greenish gray fine- and medium-grained tuffaceous sandstones, with carbonate material,containing abundant gastropod and bivalve shells, plantdetritus, and rare fragments of reptile bones. Thesesandstones are interbedded with siltstones containingplant remains. The presence of fragmentary reptilebones in these beds (Cape Sedlovidnyi) was first estab-lished in an unpublished report by N.A. Belyaevskiiand V.D. Prinada (1948). They found a relatively largefragment of a reptile bone (at least 45 cm long) incoarse-grained (gravellike) sandstones forming inter-beds in massive dense medium-grained sandstones inthe northern extremity of the Cape Sedlovidnyi (Khan-gan). This was the first finding of reptile bones in theNikanskaya Beds of southern Primorye. Subsequently,in the explanatory note to the geological map of Pri-morye, scale 1 : 500000 [5, p. 123], it was indicatedthat “…in siltstone deposits considered, vertebrates arerepresented by unidentifiable fish remains (scale andgill covers) and an imprint of a vertebral column, whilesandstone deposits have yielded large fragments of rep-tile bones.” Siltstones of these strata yielded conchost-racans, ostracodes, freshwater gastropods and bivalves,and plant imprints. From 2001 to 2003, V.S. Markevich,E.V. Bugdaeva (Institute of Biology and Soil Sciences,Far East Division, Russian Academy of Sciences), andYu.L. Bolotskii (AMURKNII) collected fish imprintsand unidentifiable fragments of reptile bones in out-crops on capes Palets and Sedlovidnyi.The strata described extend in northeast directionfrom Cape Sedlovidnyi (Andreev Bay) on the easterncoast of Ussuriiskii Gulf to the village of Novonezhino(Sukhodol River Basin) over a distance of more than20 km. Belyaevskii and Prinada (report, 1948)described bone-bearing beds in the green siltstonestrata dated Early Cretaceous. Subsequently, thesedeposits were assigned to the Cenomanian–Santonian(97–83 Ma) [5]. As a result of geological survey(1 : 200000), these strata were later assigned to theFrentsevka Formation dated Albian–Cenomanian(112–93 Ma) [6]. At present, these strata are recognizedas the separate Kangauz Formation dated Middle–LateAlbian (105–98 Ma) [7]. The Kangauz Formation iscomposed of siltstones, sandstones, tuffites, and con-glomerates and occurs on the eastern coast of Ussuri-iskii Gulf.The vertebra (Fig. 2) is platycelous, with circulararticular facets. The ventral side of the vertebral cen-trum is 23.5 mm long. The greatest height of the verte-bra, including the neural spine, is 48 mm. The posteriorarticular facet of the vertebral centrum is slightlyoblique. Its ventral margin, along with the articular fac-ets for the haemal arch, are broken off. The transverseprocess is stout, its base occupies the ventral area of theneural arch and the dorsal area of the vertebral centrum.The distal end of the transverse process expandsabruptly dorsoventrally. The transverse process is39 mm long. The vertebral foramen is relatively small.The prezygapophyses are broken off. The postzygapo-physes are shifted close to one another, located near themidheight of the neural arch. Anteroposteriorly, the

Sequence architecture and carbonate platform configuration (Late Cenomanian–Santonian), Sinai, Egypt

Abstract Relative sea‐level changes on the mixed carbonate–siliciclastic platform of Sinai are manifested in shifts of distinct facies belts (deep‐water facies, high‐energy subtidal, shallow subtidal, lagoon, shallow shoreface siliciclastics, supratidal) and are interpreted in terms of sequence stratigraphy. Eight sedimentary sequences are recognized for the Upper Cenomanian to Santonian. Their correlation along a north–south transect reveals distinct changes in lithofacies and progradation/retrogradation patterns within the individual systems tracts. The number and stratigraphy of the sequence boundaries of Sinai correlate well with those from adjacent areas. Patterns of increased subsidence are documented for the Central Sinai Basin since the Late Cenomanian by increased thickness of the stratal packages (post‐CeSin 7 HST, post‐TuSin 1 LST and HST, post‐TuSin 2 LST) and are balanced by varying accumulation rates. Based on new sedimentological and biostratigraphic data, large‐scale palaeogeographic maps and cross‐sections show the: (1) temporal and spatial evolution of the Central Sinai Basin, e.g. its latest Cenomanian initial formation, Lower Turonian deep‐water facies, Middle Turonian to Coniacian synsedimentary subsidence; (2) drowning of the Cenomanian platform coinciding with the latest Cenomanian to Early Turonian relative sea‐level rise; (3) re‐establishment of the platform in Middle–Late Turonian times; and (4) a Coniacian basin and swell morphology.

Lithostratigraphy and biostratigraphy of the Cenomanian–Santonian strata of Sinai, Egypt

The Cenomanian–Santonian successions of Sinai mainly consist of inner-shelf siliciclastics and carbonates. Five formations (Halal, Raha, Abu Qada, Wata, Matulla) have been recognized and a multibiostratigraphic framework has been constructed. The biostratigraphic assignments of the formations are mainly based on calcareous nannofossils. Their semiquantitative distribution within nine sections is presented, enabling us to identify the biozones CC10–CC16 in some cases. Ammonites are abundant in the uppermost Lower Turonian Mammites nodosoides Zone only. Planktic foraminifera of the Coniacian–Santonian Dicarinella concavata and D. asymetrica zones have been found. In addition to these groups, ostracods are used to differentiate between the stages supplemented by data in the literature on benthic foraminifera and rudists. Some modifications of previous lithostratigraphic schemes are proposed for the sections studied: from the ammonite data, a hiatus is proposed between the Halal/Raha and Abu Qada formations (Cenomanian/Turonian boundary); the Abu Qada Formation is considered to range from the M. nodosoides Zone to the lowermost Upper Turonian; and the base of the Matulla Formation is uppermost Turonian (CC13). A combined lithostratigraphic and biostratigraphic correlation of ten sections along a N-S transect allows the differentiation of eleven stratigraphic units. Units 1–8 within the Cenomanian–Turonian Halal, Raha, Abu Qada and Wata formations are considered to be synchronous. In contrast, ‘Syrian Arc’ tectonics most probably led to diachronous deposition of units 9–11 within the Coniacian–Santonian Matulla Formation.

Nonmarine Cretaceous bivalve assemblages in China

Bivalve fossils are very abundant in nonmarine Cretaceous rocks in China. Six assemblages are documented: Nakamuranaia-Margaritifera ( Mengyinaia)- Neomiodonoides and Peregrinoconcha-Koreanaia-Pseudohyrioides (Berriasian-Barremian); Trigonioides (T.)-Plicatounio (P.)-Nippononaia (N.) (Aptian-Albian); Plicatounio (P.?)-Maninsonella-Kwanmonia (?) and Trigonioides (Hoffetrigonia)-Trigonioides (Kumamotio?)-Plicatounio (P.) (Cenomanian Santonian); and Pseudohyria-Sainshandia Limnocyrena (Campanian-Maastrichtian). During the Early Cretaceous there appears to have been provincialism of these assemblages, notably the second-named assemblage which is limited to the extreme southwest of China.