Abstract Large earthquakes and related tsunamis serve as triggering mechanisms that generate turbidity currents which form turbidites. The event deposits from the recent 2011 Tohoku-oki earthquake and tsunami are observed throughout a wide area along the Pacific coast of Tohoku, northern Japan, extending from the coast through the shelf and slope, to the trench floor. Spatio-temporal correlation of turbidites and other tsunamigenic deposits, such as those generated in the 2011 event, can be used to reconstruct the recurrence history of large earthquakes and tsunamis. Here we use sediment cores and sub-bottom profiles to analyse the depositional setting along the Japan Trench, and show that the environment is ideal for preserving turbidites. The subducting Pacific Plate creates graben or basins along the trench floor that accommodate the episodic deposition of fine-grained turbidites; and interseismic hemipelagic deposits that form with high sedimentation rates along the Japan Trench effectively cover earthquake-induced turbidites and preserve the deposits as a geological record of large earthquakes. Therefore, small deep-sea basins with high sedimentation rates, such as in and around the Japan Trench floor, are favourable environments for studies of turbidite palaeoseismology.

Environmental changes linked to Deccan volcanism are still poorly known. A major limitation resides in the paucity of direct Deccan volcanism markers and in the geologically short interval where both impact and volcanism occurred, making it hard to evaluate their contributions to the mass extinction. We investigated the low-magnetic-susceptibility interval just below the iridium-rich layer of the Bidart (France) section, which was recently hypothesized to be the result of paleoenvironmental perturbations linked to paroxysmal Deccan phase 2. Results show a drastic decrease of detrital magnetite and presence of scarce akaganeite, a hypothesized reaction product formed in the aerosols derived from reaction of a volcanic plume with water and oxygen in the high atmosphere. A weathering model of the consequences of acidic rains on a continental regolith reveals nearly complete magnetite dissolution after ~31,000 yr, which is consistent with our magnetic data and falls within the duration of the Deccan phase 2. These results highlight the nature and importance of the Deccan-related environmental changes leading up to the end- Cretaceous mass extinction.

The Campanian Manson impact structure of Iowa represents the best-preserved, large-diameter complex crater within the continental United States. The related bolide struck from the southeast at a low angle, potentially distributing ejecta downrange to the northwest across the Western Interior Cretaceous Seaway. Here, we (1) examine possible correlation of Manson impact horizons across the Cretaceous seaway to terrestrial formations of Montana, and (2) test a large hadrosaur bone bed from the Two Medicine Formation for evidence indicative of the Manson impact. The study includes geochronology; palynomorph, soot, and geochemical analyses; and physical searches for impact ejecta. The impact ejecta–bearing Crow Creek Member of the marine Pierre Shale can be correlated to the SB2 discontinuity in the Judith River and Two Medicine Formations of Montana based on radiometric dates, ammonite zonation, and an association with the onset of the Bearpaw transgression. A 40 Ar/ 39 Ar analysis of an associated bentonite bed dates the hadrosaur bone bed (TM-003) to 75.92 ± 0.32 Ma referenced to MMhb-1 at 523.1 Ma. This bentonite and associated lacustrine units suggest a potential correlation with the SB2 and the Crow Creek Member. However, our examination of the bone bed produced no definitive impact evidence. The combined analyses did reveal three unusual aspects: (1) an abundance of Ulmoideipites sp., (2) a high soot content, and (3) elemental and mineralogical changes suggestive of distinct geochemical units. A major wildfire followed by a postcatastrophe bloom dominated by Ulmoideipites sp. likely preceded the eventual debris flow that generated the bone bed. The SB2 discontinuity and the 33n.3r magnetic subzone represent traceable stratigraphic markers that could serve as guides in future exploration for Manson impact evidence in terrestrial formations west of the seaway.

Results are presented of fieldwork and laboratory analyses on the volcanostratigraphy of the Ürgüp Formation in the Central Anatolian volcanic province, Cappadocia, Turkey. The formation of late Miocene to early Pliocene age is exposed in areas of the Ürgüp Basin and Nevşehir Plateau. It consists of volcaniclastic and epiclastic members with intercalated local basaltic to andesitic lava flows and scoria. The volcaniclastic members are composed of widespread covers of voluminous rhyolitic, less often dacitic, low-aspect ignimbrites and unconsolidated Plinian air-fall pumice layers. Intercalated abundant terrestrial and/or lacustrine sedimentary successions occur, which are dominated by lahars in the south and carbonates or diatomites in the north, respectively. Based on field, mineralogical, and geochemical evidence, a number of revisions are suggested by our studies, two of which are presented and discussed here: (1) the new correlation of the former “Sofular Ignimbrite” with the ignimbritic bed of the Sarimaden Tepe Member, and (2) the identification of a widespread pair of Plinian air-fall pumice lapilli beds, tentatively called Güzel Dere Member. It can be correlated with the former stratigraphic units “Tilköy Fall” and “Karain Fall.” The Tilköy Fall is recognized as a local remnant in an unconformity-bounded stratigraphic profile, and the Karain Fall unit is recognized as a set of reworked pumice-enriched layers in a lacustrine sediment pile. From complete terrestrial sediment sections, we identified the stratigraphic position of the Güzel Dere Member between the ignimbritic Cemilköy and Tahar Members. The pumice layers provide a new marker horizon for external epiclastic profiles in Central Anatolia not reached by ignimbrites.