ABSTRACT The Cretaceous-Paleocene (K/P) boundary intervals are rarely preserved in successions of shallow-water limestones. Here, we describe a shallow rocky shore on the active orogenic wedge of the eastern Alps (Austria) fringed by a carbonate platform that was largely cannibalized by erosion. We compared this succession with similar nearshore environments globally, as well as the deep sea, to gain a better understanding of the environmental response to the K/P boundary transition. In the eastern Alps, Cretaceous and Paleocene lithofacies across the K/P boundary transition are separated by a hardground that formed during subaerial exposure and that terminates Upper Maastrichtian limestone with planktic foraminiferal assemblages deposited at neritic depth during zone CF3 (ca. 66.500 Ma). Above the hardground, there are beachrocks with early Danian zone P1a(1) assemblages, which indicate the hardground spans about ~600 k.y. of nondeposition and/or erosion. During the early Danian, the marine transgressive fringe fluctuated between “shoreface to emersion” environments, depositing limestones rich in bryozoans, rhynchonellids, coralline algae, and rare planktic foraminifera along with abraded, bored, and/or encrusted clasts eroded from older rocks. Repeated short subaerial exposure is marked by vadose diagenesis and hardgrounds, including an ~1.5 m.y. interval between magnetochrons C29n to C28n and planktic foraminiferal zones P1b to P1c(2). Comparison with platform carbonate sequences from Croatia, Oman, Madagascar, Belize, and Guatemala, as well as nearshore siliciclastic environments of southern Tunisia, Texas, and Argentina, across the K/P boundary transition revealed surprisingly similar deposition and erosion patterns, with the latter correlative with sea-level falls and repeated subaerial exposure forming hardgrounds. Comparison with deep-sea depositional patterns revealed coeval but shorter intervals of erosion. This pattern shows a uniform response to the K/P boundary transition linked to climate and sea-level changes, whether in shallow nearshore or deep-sea environments, with climate change tied to Deccan volcanism in magnetochrons C29r-C29n.

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 Upper Cretaceous reefs were concentrated in low- to mid-latitude regions in the Northern Hemisphere between the Americas and the Arabian Peninsula. Rudist bivalves, scleractinian corals, sponges, stromatoporoids, and algae were the dominant biota. Most Late Cenomanian through Santonian reefs occurred in low paleolatitudes (0–30° N) and were dominated by rudist bivalves. North of 30°, reefs constructed of corals, stromatoporoids, and siliceous sponges outnumbered those of bivalves. Campanian through Maastrichtian reefs occurred between the equator and 30° N and were also dominated by bivalves, whereas corals and bryozoans dominated the northern occurrences. The distribution of Upper Cretaceous reefs was analyzed with respect to paleogeography, surface current circulation patterns, sea level, and sea-water chemistry. Considering the paleogeographic setting of the Late Cretaceous, westward-flowing surface currents accounted for the low- to mid-latitude distribution patterns of reefs, whereas northward surface currents could account for northern occurrences in the European and North American regions, especially during sea-level highstands when shelfal areas were flooded. There is a global correspondence between the development of Upper Cretaceous reefs and the first-order sea-level highstand of Haq et al. (1987) , but there is only a regional, not global, correlation between reefs and second-order sea-level fluctuations; some reefs were associated with third-order and fourth-order fluctuations. We found no direct correspondence between the global distribution of Upper Cretaceous reefs and oceanic anoxic events, salinity, aragonite-calcite seas, or sea-surface temperature, although links still need to be investigated for geographic regions and subdivisions of the Late Cretaceous. Numerical analyses of the PaleoReef database allowed for an assessment of the biological and physical attributes of reefs. From this database, Upper Cretaceous reefs representing the Upper Zuni 111 supersequence (Late Cenomanian-Santonian) can be characterized by rudists of the constructor guild. Other biota are also prominent. Biostromes and reef mounds in shallow intraplatform or platform-margin settings have large amounts of micrite and a moderate debris potential. Reefs representing the Upper Zuni IV supersequence (Campanian-Maastrichtian) can be characterized by rudists and oysters of the constructor guild. Other biota areprominent. Biostromes and reef mounds in a marginal marine setting have large to moderate amounts of micrite and a moderate debris potential.

Abstract Name: Maiella platform Authors: Gregor P. Eberli, Daniel Bernoulli, Diethard Sanders, and Adam Vecsei Location: From 42° 05' to 07' north latitude and 14° 08' to 09' east longitude, provinces of Aquila, Chieti, and Pescara, Italy Geologic time interval: Early Cretaceous-late Miocene Tectonic-sedimentary setting: Southern continental margin of Jurassic-Cretaceous Tethyan ocean, part of large late Tertiary sedimentary decollement nappe of the Southern Apennines, exposed in a broad frontal anticline Basin type: Passive continental margin Paleoclimate: Generally warm and only seasonally humid, some humid intervals (bauxite); paleolatitude was 10° to 30° north Platform type: Part of isolated platform with escarpment Platform geometry: Escarpment changing to low angle slope and distally steepened ramp. Thickness is 2000 m (Lower Cretaceous-upper Miocene). Length exposed north-south is approximately 30 km, probably corner of the large Apulian platform, which is largely buried below Tertiary rocks, approximately more than 400 km (750 km?) long. Width exposed is 10–15 km. Facies and fossils: Cretaceous shallow water platform margin in the south and a pelagic facies (Scaglia) with intercalated gravity flow deposits in the north, separated by an escarpment. Late Cretaceous platform margin rimmed by rudist biostromes (Hippurites and Caprinides) Systems tracts and stacking patterns: Unconformities and exposure surfaces separate sequences; onlap and downlap patterns occur in the sequences. Platform highstand systems tracts composed of aggradational and progradational parasequences with rudist biostromes at the margin. Basin assemblage of pelagic deposits and turbidites (biodetritus) deposited during sea level highstands. Lowstand systems tracts have incised channel fills, small slope fans, and gravity flow deposits. Transgressive systems tracts hard to distinguish from highstand systems tracts.