Abstract The International Geoscience Programme Project IGCP 609 addressed correlation, causes and consequences of short-term sea-level fluctuations during the Cretaceous. Processes causing several ka to several Ma (third- to fourth-order) sea-level oscillations during the Cretaceous are so far poorly understood. IGCP 609 proved the existence of sea-level cycles during potential ice sheet-free greenhouse to hothouse climate phases. These sea-level fluctuations were most probably controlled by aquifer-eustasy that is altering land-water storage owing to groundwater aquifer charge and discharge. The project investigated Cretaceous sea-level cycles in detail in order to differentiate and quantify both short- and long-term records based on orbital cyclicity. High-resolution sea-level records were correlated to the geological timescale resulting in a hierarchy of sea-level cycles in the longer Milankovitch band, especially in the 100 ka, 405 ka, 1.2 Ma and 2.4 Ma range. The relation of sea-level highs and lows to palaeoclimate events, palaeoenvironments and biota was also investigated using multiproxy studies. For a hothouse Earth such as the mid-Cretaceous, humid–arid climate cycles controlling groundwater-related sea-level change were evidenced by stable isotope data, correlation to continental lake-level records and humid–arid weathering cycles.

Abstract Deep-time sea-level oscillations in the Milankovitch-band of orbital cyclicities govern deposition in the pelagic realm mainly by varying siliciclastic input. Pelagic sediments from the Cretaceous greenhouse climate phase provide a valuable archive for sea-level change. Although sea-level variations are of negligible amplitude compared with depositional water-depths, direct physical proxy data are based on higher and coarser siliciclastic input during sea-level lowstand and regressions, and include coarser grain size and grain-size parameters as well as the heavy mineral and clay content. Chemical proxies that relate to siliciclastics are manganese, titanium and zirconium, often normalized v. aluminium. Further proxies provide the ratios of strontium v. calcium, controlled by shelf carbonate erosion, and partly redox-sensitive elements like uranium and thorium. From a mineralogical point of view, the total amount of siliciclastics and their diversity relating to heavy minerals provides sea-level information in hemipelagites, as well as the phyllosilicate content v. biogenic pelagic background deposition of carbonate and siliceous microfossils in pelagites. In addition, measurements of gamma ray emission, linked to U, Th, K content and magnetic susceptibility may relate to sea-level cycles and various other more climate-dependent proxies like oxygen isotopes of fossil calcite and compositional maturity of hemipelagic sediments.

Abstract Upper Cretaceous strata at Göynük, northwestern Anatolia, Turkey, provide a geological record of the Campanian–Maastrichtian from the Sakarya Terrane along the active Neotethys margin. Shales and shaly marls with siliciclastic and volcaniclastic intercalations indicate a pelagic palaeoenvironment rich in planktonic and benthonic foraminifera and calcareous nannofossil assemblages. A composite record from the Campanian to the Maastrichtian records nannofossil standard zones UC15c (CC21) to UC20a (CC26) as well as the Globotrunanella havanensis planktonic foraminifera Zone to the Racemiguembelina fructicosa planktonic foraminifera Zone. The complete ‘mid’-Campanian to early Maastrichtian composite section can be correlated to other western Tethyan sections. The Campanian–Maastrichtian boundary is positioned between the first occurrence of the planktonic foraminifera Gansserina gansseri and the last occurrence of the nannofossil Uniplanarius trifidus . Clastic input and higher sedimentation rates constrain regional sea-level lowstands around the late Campanian calcarata Zone and the Campanian–Maastrichtian boundary, corresponding to the Campanian–Maastrichtian boundary event.

Abstract The interplay of Late Cretaceous basin subsidence and oscillations in sea level produced a mixed freshwater–marine succession within the Upper Cretaceous Gosau Group of the Northern Calcareous Alps. Cored sections from wells of the Glinzendorf and Gießhübl Syncline, as well as sediments from the outcrop area of Grünbach–Neue Welt and Slovakian equivalents have been investigated for their stable isotopic composition. Bulk carbonate δ 13 C and δ 18 O values of 116 fine-grained samples (shales, siltstones, marls) and 87 Sr/ 86 Sr values of 10 samples from the borehole Markgrafneusiedl T1 were analysed in order to distinguish between non-marine and marine deposits and to compare and correlate isotope characteristics of the different Gosau synclines and basins. Non-marine samples have significantly lower mean δ 13 C values compared to the mean of marine samples. The discrimination between a marine and non-marine group using δ 18 O is also highly significant statistically, even though the difference between the average non-marine and marine values is small. Strontium isotope values of marine intervals are near the range of values of normal Upper Cretaceous sea water but show a trend towards higher ratios in marginal marine and non-marine deposits. Although diagenesis and the detrital carbonate admixture partly influence the isotopic composition, the original environmental signal can still be reliably identified.

Corb Definition Cretaceous oceanic red beds—CORBs—are reddish to pinkish to brownish sedimentary rocks, of Cretaceous age, deposited in pelagic marine environments. Generally these are limestone, marl, shale, and/or chert.

Abstract Cretaceous oceanic red beds (CORBs) are mainly pelagic red shales, marls, or fine-grained limestones. These facies have been the subject of two closely related International Geosciences Programs GCP 463 and 494. They are a significant facies of deep-water pelagic deposits and pelagic-hemipelagic sedimentary systems. A major contribution of these two three-and five-year projects is that CORBs are globally distributed in outcrops in Europe, Asia, Africa, New Zealand, Caribbean, and at DSDP and ODP sites in the Tethyan Atlantic, Pacific, and Indian oceans. CORBs experienced two paleogeographical expansions, (1) in Aptian nannofossil zone CC7 shortly after the OAEla and (2) in Turonian zone CC11 after the OAE2, respectively. Lower Cretaceous CORBs are much less common than Upper Cretaceous. Above OAE2, CORBs in zone CC11 crop out in 25 basins or tectonic zones; CORB distribution is greatest in Coniacian-Early Santonian zones CC13-CC15 in up to 34 basins or tectonic zones in the world. The ages of CORBs are constrained by paleontological data including planktic foraminifera and nannofossils in calcareous CORBs, and agglutinated foraminifera and dinoflagellates or radiolaria in noncalcareous CORBs. The biostratigraphic data were assembled into an integrated, testable data base by graphic correlation. The data base was then correlated to GSSPs and reference sections of Cretaceous stages. Three general facies types of CORB are defined using the end members clay, carbonate, and chert: deep-water red claystones deposited below the calcite compensation depth, red hemipelagic and pelagic carbonates, and red cherts and radiolarites. The depositional environment of most CORB units was in relatively deep oceanic basins. Deposition was generally far from shoreline and only locally associated with coarse terrigenous clastics such as turbidites. Significant controlling factors of CORBs were slow sediment accumulation rates at great paleo–water depths. Like most marine sediments, CORBs are a complex mixture of terrigenous detritus and seawater-derived material. According to data reported from the studied localities, the common geochemical properties of CORBs are their extremely low organic-carbon content and high level of ferric oxides. The ratio between ferric oxides to the total iron is not only higher than the level of adjacent non-red sediments, but also higher than that of Phanerozoic normal marine oxic sedimentary rocks. These chemical properties indicate that CORBs were deposited in environments that were highly oxic at or below the sediment-water interface. Other major and trace elements and isotopic data suggest an oxic, oligotrophic water mass having overall low productivity. The paleoceanographic and paleoclimatological conditions are corroborated by carbon stable-isotope data, phosphorus burial records, dissolved-oxygen index, and comprehensive geochemical modeling results. Paleoclimate, paleogeography, ocean currents, and nutrient flux, among other processes, were related to the deposition and wide distribution of CORBs during the Late Cretaceous. The development of the paleogeographic configuration and Late Cretaceous climate cooling provided the basis for increasing ventilation of the deep ocean. The behavior of redox-sensitive nutrient elements like phosphorus further stimulated the development of oligotrophic conditions. All of these factors contributed to the global distribution of CORBs.

Abstract An integrated, testable chronostratigraphic database of Late Cretaceous bioevents in numerous reference sections was constructed in order to test the global synchrony of Upper Cretaceous oceanic redbeds—CORBs—and to measure precisely their rates of sediment accumulation. Graphic correlation was the method of choice because it is based on species checklists and because the range projections are transparent and testable. Stage boundaries are defined by GSSP or key reference sections with ammonites, planktic foraminifera, and nannofossils, as well as with magnetochrons. Sequence boundaries and other sedimentary markers as defined in reference sections are projected into the database by graphic correlation of the co-occurring fossils. The database scale is calibrated to radiometric ages of Upper Cretaceous stages that are generally similar to those of the 2004 time scale. This database is used in three areas to interpret deposition of CORBs, the North Atlantic, the Swiss Pre-Alps, and the Eastern Austrian Alps. North Atlantic CORB intervals in six cores range in age from Turonian to Maastrichtian. This succession was deposited within two distinct deep water masses. A Turonian–Santonian oxygenated water mass with a relatively shallow calcite compensation depth (CCD) hosted red-bed deposition and diversification of benthic foraminifera. Deep-water, low pH conditions existed in the North Atlantic during Late Cretaceous submarine volcanism. The well oxygenated Campanian–Maastrichtian water mass was above the CCD, and calcareous fossils were preserved during a second benthic foraminifer diversification event. Red marine clay and turbidites alternated with gray and green beds. Rates of sediment accumulation generally were higher during the Campanian–Maastrichtian period than during the earlier period. CORB strata in the Swiss Pre-Alps were deposited at different times in different places for varying durations and at different rates beginning in the Aptian and continued sporadically into the Santonian. In the Eastern Alps Upper Cretaceous marine red beds are interbedded with siliciclastic and calcareous facies deposited in the Penninic Ocean between colliding plates. Oldest CORB deposition is recorded in the Albian and became persistent during the Campanian. Interbedded red and gray strata record climatic forcing during tectonically controlled transgressive events. The duration of CORB deposition generally was shorter in epicontinental basins than in oceanic basins, but the average rate of sediment accumulation tended to be similar in epicontinental and oceanic basins. Even-bedded CORBs were deposited at the sameaverage duration as homogeneously bedded deposits, but even-bedded CORBs accumulated faster than homogeneous deposits. Many repetitively interbedded oceanic red beds were deposited at rates close to orbital frequencies and may have been related to climatic forcing.

Abstract: Sedimentological studies of Cretaceous deep–sea sediments deposited in the western Tethys allow at least rough analyses of the Earth Systems processes involved. The deep–sea evidence shows that the change from Lower Cretaceous pelagic carbonates to mid–Cretaceous black shales was not a sudden event, but took 15 Myr for a complete transition. This change was a response to thermal subsidence of oceanic crust in the western Tethys. The mid–Cretaceous black–shale development was forced by high deposition of organic matter in a response to a humid, warm climate, with the latter in turn resulting in decreased rate of deep water formation, poor ventilation, and lower content of dissolved oxygen in deep waters. However, the bottom waters remained oxic and/or variably dysoxic, as indicated by presence of mid–Cretaceous greenish–gray claystones in the Moroccan basin, while elsewhere black shales were deposited, and by local bioturbation and intercalated reddish, oxic horizons. Various processes were involved in the origin of oceanic anoxic events (OAE1a and OAE2). Sediments deposited during these events were laid down during onset of major transgressions in the central North Atlantic and thus can be viewed as condensed horizons related to flooding events. The high content of organic matter is most probably a phytoplankton response to ocean surface water fertilization by iron during extensive Aptian volcanic activity along North Atlantic continental margins. Less certain is the influence of the Caribbean igneous plateau (93–89 Ma) and Madagascar flood basalts on the development of OAE2. The reddish colors of the overlying Upper Cretaceous pelagic claystones and shales are of early diagenetic origin and not a depositional feature. Sediment oxidation was forced by low sedimentation rate of 20 mm/kyr, driven by eustatic sea–level rise and increased ventilation of the basin. The red beds intercalated in mid–Cretaceous strata in western Tethys have variable origins, such as 1) an inflow of higher–salinity surface waters from the southern Atlantic when the equatorial seaway began to open; 2) reduction of sedimentation rate as a result of local tectonics; and 3) sea–level changes. Less certain is whether a temporary inflow of colder, more oxygenated bottom water into small tectonic sub–basins of the Mediterranean region could have resulted in bottom–sediment oxidation, because the validity of such a hypothesis cannot be confirmed by studies of modern marine sediment.

Abstract: CORBs are described from a north-south transect from the passive European margin with the Helvetic–Ultrahelveticshelf and continental slope through the Alpine Tethys, including the Rhenodanubian Flysch Zone into the southern, tectonically active margin of the Austro–Alpine microplate, including the Northern Calcareous Alps. In the Helvetic (shelf) and Ultrahelvetic (slope) part of the European margin, the proportion of CORBs in the Upper Cretaceous successions increases significantly with increasing water depth and increasing pelagic character. In the Ultrahelvetic units of Upper Austria (Rehkogelgraben, Buchberg), CORBs define a continuous red interval from the Lower Turonian to the Lower Campanian. The onset of CORB deposition in the Ultrahelvetic Zone corresponds to a major change in paleoceanographic conditions from anoxic during the Late Cenomanian OAE 2 to highly oxic during the Early to Middle Turonian. In the Rhenodanubian Flysch, hemipelagic red and green shales alternate with turbiditic siltstones and minor sandstones in the Upper Aptian–Lower Cenomanian Lower Varicolored Marls, the Coniacian–Lower Campanian Seisenburg Formation, and the uppermost Campanian Perneck Formation. CORBs in the Rhenodanubian Flysch are controlled mainly by tectonic events and sea-level changes, and occur during times of transgressions, low clastic input, and low turbidite frequencies. In the Austro–Alpine Northern Calcareous Alps, CORBs occurfrom the Santonian onwards in the upper parts of transgressive sequences of the Gosau Group, e.g., in the Tiefenbach and the Dalsenalm sections. In areas where clastic input was low, CORB deposition continued up into the Maastrichtian. Based on these data a peak of oceanic red beds is inferred for the middle Santonian–Early Campanian time interval. Prerequisites for CORB sedimentation are low clastic input, low sedimentation rates, and increasing paleo–water depth. CORBs can be classified as a variation of three end members: clayey CORBs, consisting mainly of terrigenous clay minerals; calcareous CORBs, mainly pelagic limestones; and siliceous CORBs, consisting mainly of biogenic SiO 2 .

Abstract We studied two sets of Lower Cretaceous pelagic red beds (CORBs) in the Northern Calcareous Alps in the northwestern Tethys. Red pelagic calcareous intervals are known from the Anzenbach Member of the Schrambach Formation and from the base of the overlying Tannheim Formation. Biostratigraphic data from the Anzenbach Member, a several–meters–thick red marly to marly limestone interval within gray pelagic limestones south of Salzburg, indicate a Late Berriasian to Early Valanginian age. Red Hedbergella limestones form the base of the Tannheim Formation, and, together with overlying red and gray marlstones, give a Late Aptian to earliest Albian age, confirmed by strontium isotope stratigraphy. Whereas the Hedbergella limestones are interpretedas a condensed facies due to regional basin morphology, the other two CORB intervals coincide with cold periods in the Early Cretaceous, suggesting a causal link between cool climate and CORB deposition. Ephemeral ice sheets during icehouse interludes may have enhanced the formation of oxygenated bottom waters in high latitudes.

Abstract Study of the Upper Cretaceous oceanic red beds (CORBs) in the Outer Western Carpathians, Czech Republic, was based on integrated biostratigraphy (foraminifera, dinoflagellata, calcareous nannofossils). Agglutinated foraminifers are the only abundant microfossil group in red shale. Reconstruction of the sedimentary paleoenvironment was supported by mineralogical and paleoichno-logical analysis. Bioturbation and lack of organic matter indicate highl oxic sedimentary conditions. The CORBs range from the Albian to the Lower Paleocene. Both their bases and their tops are heterochronous through individual facies zones of the Outer Carpathians. Generally, the time span of the CORBs decreases from abyssal to slope facies and from inner to outer zones. The CORBs reached their maximum extent during the Turonian. The CORBs were terminated by increased influx of terrigenous organic matter. Key words: Outer Carpathians, red beds, Cretaceous, dinoflagellates, agglutinated foraminifera, calcareous nannofosils, ichnofossils

Abstract: Three Cretaceous oceanic red-bed (CORB) successions from the Eastern Carpathians of Romania were studied in detail to determine their age and depositional environments. Our investigations revealed that the studied CORBs display a variety of lithofacies, such as red shales, red radiolarites, red cherts with radiolarians, red cherts, and red claystones and marlstones with microfossils. The CORBs of the Eastern Carpathians encompass the latest Albian-Coniacian interval, based on calcareous nannofossil analyses. But the main part of the CORBs is carbonate free or has very low carbonate content; the upper part becomes increasingly more calcareous. The CORBs average 60% SiO 2 , and also includes a high amount of Fe 2 O 3 which suggests an oxic deep marine environment. The CORBs of the Eastern Carpathians, overlying Albian black shale lithofacies, are similar in lithology and age to other Tethyan CORBs. CORB deposition indicates significant paleoenvironmental changes, from an anoxic setting to an oxic one, across the Early-Late Cretaceous boundary interval. KEY WORDS: Eastern Carpathians, CORBs, lithofacies, biostratigraphy, paleoenvironment

Abstract: The uppermost Cretaceous marine red beds from the Romanian Carpathian bend area were investigated in detail from the lithostratigraphic and biostratigraphic points of view. Geochemical and mineralogical investigations were performed along the same profile. The investigated sequence spans the Upper Campanian and the whole Maastrichtian stages, including the K-T boundary, as evidenced by the nannofloral mass extinction and the well known carbon isotope excursion. Both qualitative and semiquantitative calcareous nannofossil studies were conducted. The semiquantitative investigations focused on six taxonomic groups, such as Watznaueria barnesae, Micula spp., Boreal nannofossils, Tethyan nannofossils, Braarudosphaera bigelowii, and the calcareous dinoflagellate genus Thoracosphaera. The new data indicate constant δ 13 C values in the Upper Campanian and Lower Maastrichtian red marls of the Gura Beliei Formation. In the Upper Maastrichtian deposits of the Ialomica section, lithological and mineralogical changes, together with several negative δ 13 C and δ 18 O excursions, suggest instability of the ecosystems, fluctuating sea level, and/or detrital input as well as climatic changes during the Late Maastrichtian interval. The age and the lithology of the Gura Beliei red beds are similar to other red beds deposited in the Tethys Realm (i.e., the Nierental Formation of Austrian Northern Calcareous Alps, the Puchov Marl of the Slovakian and Polish Western Carpathians, the Vojvodina region of Serbia, and the Scaglia Rossa of Apennines).

Abstract: The deep-water Pindos Basin was characterized by siliceous sedimentation during Jurassic-Cretaceous times. Cretaceous siliceous oceanic red beds, i.e., red cherts and radiolarites 25 to 100 m in thickness, are present in the Katafito Formation (Valanginian-Coniacian), whereas the overlying Upper Cretaceous Platy Limestone Formation is characterized by red and gray pelagic carbonates and turbidites. The Katafito Formation consists of siliceous red claystones, ribbon radiolarites, cherts to marly claystones with an apparent red-green cyclicity, silicified mud, and radiolarian-sand turbidites. Sedimentation rates vary between 0.5 and 1.5 mm/kyr. In the siliceous CORB succession, five green to black levels have been recognized, composed of greenish claystones, mudstone turbidites, green to black layered or nodular cherts, and distinct black shales. These green to black intervals can be correlated to oceanic anoxic events, namely, the Late Valanginian Weissert Event, a latest Barremian event, and the Early Aptian OAE 1a, the Late Aptian to early Albian OAE 1b, and the Late Albian OAE 1c and OAE 1d events. From the Middle Cenomanian onwards, turbidites and mass-flow deposits increase in number, but red radiolarites remain the normal background sedimentation in the Pindos Basin. The overlying red marlstones and limestones of the basal Platy Limestone Formation, starting diachronously in the Coniacian to Santonian, record a shallowing of the basin to above the calcite compensation depth and again an increase in detrital carbonate input. The siliceous red beds of the Pindos Basin and other basins in the eastern Mediterranean indicate a long-term record of oxic sedimentation during the Early Cretaceous up to the Coniacian that was punctuated only by short-term anoxia during widespread oceanic anoxic events.

Abstract Cretaceous oceanic red beds (CORBs) in New Zealand are found in Upper Cenomanian to Coniacian marine successions at a number of localities in the Raukumara Peninsula and Wairarapa (East Coast) in the North Island, and Marlborough in the South island, New Zealand. The New Zealand CORBs represent so far the southernmost occurrence of these enigmatic strata. CORBs in New Zealand are found in siliciclastic mudstone-dominated successions interpreted as emplaced by low-density turbidity currents deposited at lower bathyal depths and occur as either 0.5-6 m thick red mudstones or as 10-20 m thick intervals of interbedded red, green, and olive-gray mudstone. The onset of red-bed deposition is penecontemporaneous with the Cenomanian-Turonian boundary and a possible biotic signal, manifested as a rapid decline of macrofauna at the onset of red-bed deposition, culminating in a barren section coincident with the acme of CORB formation. No signal of the Bonarelli OAE2 Event is known from sedimentary rocks in New Zealand.

Abstract: The Söhlde Formation (Upper Cenomanian-lower Upper Turonian) of Lower Saxony and Sachsen-Anhalt is characterized by an alternation of red and white limestones of a pelagic biosedimentary system, deposited ca. 200 km distant from the nearest coastline on the European Cretaceous shelf sea at a paleolatitude around 45° N. Seven sedimentary cycles of ca. 430 ky duration can be recognized, each of which is separated by discontinuities and/or significant facies changes. White limestones and marl–limestone alternations were deposited mainly in intrashelf depressions and/or during relative sea–level highs. The red limestones were deposited on intrashelf swells above and shortly below storm wave base. Storm-and current-induced advective pore-water flow associated with low accumulation rates in a nutrient-depleted intrashelf swell setting (low C org flux into the sediment) resulted in an excess of oxygen in the sediment column and an early diagenetic window, in which ferric iron minerals were generated, causing the red pigmentation. The source of the iron was most likely clay minerals, inasmuch as a positive correlation between clay content and red pigmentation is observed. No trace of microbial activity associated with the genesis of the red color can be confirmed yet.

Abstract: A one-meter-thick marine red bed (Cretaceous oceanic red beds, CORBs) is reported from Early Turanian sediments associated with the Levant carbonate platform in central Jordan. These CORBs are of regional significance, in that deposits similar in facies and age are present in various sections of the Levant carbonate platform farther southwest in the Sinai. The red bed represents a rare shallow marine counterpart to the widely known deeper marine CORBs. The onset of sedimentation of these brick-red marls in a shallow sea (shallow subtidal) of the southern Tethys margin is shown to be synchronous with the Tethys-wide onset of marine red beds in oceanic settings in the latest Early Turonian. The transition into red marls marks a significant change in sedimentation from marly, gypsum-rich clay, representing lowstand deposits below, into a sequence including massive platform limestone beds forming a transgressive systems tract above the red bed. The sedimentary conditions on the Levant platform during red-bed deposition show some similarities to its deeper marine counterparts on the Northern Tethys margin: they are related to strongly fluctuating sedimentation rates, and they follow periods of high marine productivity, which occurred in the aftermath of OAE2. It is obvious that both strong synsedimentary fluctuations in water depth and accumulation rate and significant early and late evaporite diagenesis influenced the investigated section, so the cause of the red coloring is likely to be not solely a synsedimentary feature. The time-equivalent onset of shallow marine red beds and deep marine red beds in the Early Turonian indicates that both share common global prerequisites regardless of the paleobathymetry. Key Words: Cretaceous oceanic red beds, diagenesis, shallow marine, Levant carbonate platform, Turonian

Abstract: A major change in oceanic sedimentation from Uppermost Cenomanian organic-carbon-enriched black shales (Bonarelli Level) to predominantly Lower Turonian oceanic red beds occurred in the Tethys. This paper presents high-resolution inorganic geochemical and mineralogical data on the transitional interval from the Scaglia Bianca to the Scaglia Rossa above the Bonarelli Level of the Vispi Quarry section, Umbria-Marche basin, Italy. Limestones from the Vispi Quarry section have very low Al 2 O 3 concentrations (0.19–1.14 wt%) indicating low input of terrigenous detritus. Elements characterizing lithogenic input, such as Ti, K, Mg, Rb, and Zr, are of similar concentration in both the white limestone and the red/pink limestone and correlate positively with Al 2 O 3 , pointing to a homogeneous source area. The sources of terrigenous detrital input did not change throughout the transition from the Scaglia Bianica to the Scaglia Rossa. Geochemical data show that the red limestones were deposited under more oxic conditions, close to the sediment-water interface, as opposed to the white limestones in the Vispi Quarry section. This is supported by: (1) high Fe 2 O 3 values (0.22% in average) and high Fe 3+ / TFe ratio (0.58); (2) low values of relative enrichment factor (EF) of redox-sensitive elements U, V, Cr, Co, and Ni in the red limestones, with ratios of Ni/Co <2.5, V/Cr <1.2, V/(V+Ni) < 0.6, Fe 3 +/TFe > 0.45; and (3) a strongly negative 6Ce anomaly (0.28–0.42). The positive correlation between the peak height of hematite in the diffuse reflectance spectrophotometry (DRS) diagram and redness values (R 2 = 0.98) indicates that hematite is responsible for the color of the limestones in the Vispi Quarry section. The DRS data confirm that the red color of the Scaglia Rossa limestones is the result of low concentration (~ 0.1 wt%) of finely dispersed hematite. SiO2( excess ) P, and Ba productivity proxies show that there is no significant difference in depositional conditions and paleoproductivity levels between red limestone and white limestone. An increase in dissolved oxygen in bottom waters is the most probable cause of the origin of the red color. We suggest that intensification of bottom circulation with waters having higher content of dissolved oxygen may have resulted in significant oxidation of bottom sediments.

Abstract: This paper investigates the deposition of cyclic limestone CORBs of the Rehkogelgraben section at the passive (northern) margin of the Alpine Tethys during the Santonian with mineralogical, geochemical, and stable-isotope analyses. Mineralogical data suggest a constant source area over the investigated interval. The preservation of organic carbon is very low in this environment. The higher content of organic carbon in the Upper Santonian may indicate a regressive event in accordance with the global sea-level curve. Plagioclase and organic carbon correlate positively and might indicate enhanced input of nutrient-like trace metals during episodes of higher volcanic activity. In the Upper Santonian, terrigenous elements (Al, Li, Rb, Be) decrease upwards. Data on iron speciation for marl and limestone layers attest to oxic early diagenesis during marl deposition compared to limestone episodes. This may have been caused by varying initial TOC concentration that resulted in suboxic conditions during limestone deposition and cementation, or it might have been caused by higher sedimentation rates during limestone deposition and thus faster cementation. On the whole, geochemistry and stable-isotope data indicate a highly oligotrophic environment with efficient recycling of organic matter and nutrients in the upper water column. This is the first carbonate geochemical study of CORBs from the Ultrahelvetic Santonian. The investigated Santonian CORBs were deposited above the Late Cretaceous CCD and show that nutrient availability varied and resulted in periods of higher primary production. This might have been caused by a more proximal setting than for other CORBs from the Carpathians or from the Rhenodanubic Flysch Zone.