Abstract The Namurian and Westphalian sequences from the onshore well Scaftworth-B2, located in the Gainsborough Trough, central England, have been analysed for whole-rock inorganic geochemical data via inductively coupled plasma optical emission spectrometry (ICP-OES) and mass spectrometry (MS). The changes within key elements, and elemental ratios, results in a chemostratigraphic zonation scheme consisting of eight chemostratigraphic sequences and 13 chemostratigraphic packages, providing the type zonation for the Bowland Shale and overlying formations. Mineralogical data are provided by whole rock X-ray diffraction (XRD) and are used to calibrate the mineral modelling in order to generate a modelled mineral log for the study well. Furthermore, the modelled mineralogy is then used to calculate a relative brittleness for the samples, which can then be collaborated with traditional rock properties data at a later date. Elemental data can also be used to model the relative abundance of detrital quartz and biogenic silica; while total silicon is detected by ICP, biogenic silica is not detected by XRD owing to its amorphous nature. Enrichment factors calculated from the inorganic elemental data suggest that the sediment was deposited in an unrestricted marine setting, which experienced periods of anoxia.

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.

Sediment discharged into the portion of the Southern California Bight extending from Santa Barbara to Dana Point enters a complex system of semi-isolated coastal cells, narrow continental shelves, submarine canyons, and offshore basins. On both the Santa Monica and San Pedro margins, 210 Pb accumulation rates decrease in an offshore direction (from ~0.5 g cm −2 yr −1 to 0.02 g cm −2 yr −1 ), in concert with a fining in sediment grain size (from 4.5φ to 8.5φ), suggesting that offshore transport of wave-resuspended material occurs as relatively dilute nepheloid layers and that hemiplegic sedimentation dominates the supply of sediment to the outer shelf, slope, and basins. Together, these areas are effectively sequestering up to 100% of the annual fluvial input. In contrast to the Santa Monica margin, which does not display evidence of mass wasting as an important process of sediment delivery and redistribution, the San Pedro margin does provide numerous examples of failures and mass wasting, suggesting that intraslope sediment redistribution may play a more important role there. Basin deposits in both areas exhibit evidence of turbidites tentatively associated with both major floods and earthquakes, sourced from either the Redondo Canyon (San Pedro Basin) or Dume Canyon (Santa Monica Basin). On the Palos Verdes shelf, sediment-accumulation rates decrease along and across the shelf away from the White's Point outfall, which has been a major source of contaminants to the shelf deposits. Accumulation rates prior to the construction of the outfall were ~0.2 g cm −2 yr −1 and increased 1.5–3.7 times during peak discharges from the outfall in 1971. The distal rate of accumulation has decreased by ~50%, from 0.63 g cm −2 yr −1 during the period 1971–1992 to 0.29 g cm −2 yr −1 during the period 1992–2003. The proximal rate of accumulation, however, has only decreased ~10%, from 0.83 g cm −2 yr −1 during the period 1971–1992 to 0.73 g cm −2 yr −1 during the period 1992–2003. Effluent-affected sediment layers on the Palos Verdes shelf can be identified in seabed profiles of naturally occurring 238 U, which is sequestered in reducing sediments. The Santa Clara River shelf, just north and west of the Santa Monica and San Pedro margins, is fine-grained and flood-dominated. Core profiles of excess 210 Pb from sites covering the extent of documented major flood deposition exhibit evidence of rapidly deposited sediment up to 25 cm thick. These beds are developing in an active depocenter in water depths of 30–50 m at an average rate of 0.72 g cm −2 yr −1 . Budget calculations for annual and 50-yr timescale sediment storage on this shelf shows that 20%–30% of the sediment discharge is retained on the shelf, leaving 70%–80% to be redistributed to the outer shelf, slope, Santa Barbara Basin, and Santa Monica Basin.

The Paleogene turbiditic sedimentation in the eastern Southern Alps represents the sedimentary response to tectonic activity related to the Mesoalpine phase, which involved the surrounding chains from Paleocene time onward. Field and petrographic analyses have allowed us to classify these turbiditic successions as multisource deposits, as demonstrated by the common presence of allochemical, mainly bioclastic detritus, associated with different types of terrigenous arenites. For all units, field data suggest more proximal sources for allochemical supply and distal sources for terrigenous material, characterized by the presence of chert, carbonate rocks, and metamorphic rock fragments. All the investigated successions display transparent heavy mineral associations, marked by the common presence of chrome spinel, alkaline amphibole, staurolite, epidote, and zoisite, which point to similar metamorphic sources. The location of the source of metamorphic rock fragments is uncertain, but inputs from the internal Dinaric belt are possible. The source of the allochemical detritus was located in the nearby reactivated Friuli Platform.

The Upper Jurassic Galice Formation of the Klamath Mountains, Oregon-California, overlies the ca. 162-Ma Josephine ophiolite and the slightly younger Rogue–Chetco volcano-plutonic arc complex. The Galice Formation that overlies the Josephine ophiolite consists of a siliceous hemipelagic sequence, which grades upward into a thick turbidite sequence. Bedded hemipelagic rocks and scarce sandstone, however, also occur at several localities within the Josephine ophiolite pillow basalts. Corrected paleoflow current data suggest that the Galice Formation was derived predominantly from the east and north. Detrital modes of sandstones from the Galice Formation indicate an arc source as well as a predominantly chert-argillite source with minor metamorphic rocks. A sandstone located ∼20 m below the top of the Josephine ophiolite has detrital modes and heavy mineral suites similar to the turbidite sandstones. Detrital Cr-spinel compositions from the turbidite and intra-pillow lava sandstones are also similar, indicating supra-subduction zone mantle peridotite and volcanic sources. Published detrital zircon data from a turbidite sandstone chiefly give a bimodal age distribution of 153 Ma and ca. 227 Ma but with a minor Proterozoic component. Whole-rock geochemistry from intra-pillow lava sedimentary rocks, the hemipelagic sequence, and the turbidites suggest a mixture between mafic and cratonic sources. It is suggested that the source area for the intra-pillow lava sedimentary rocks, hemipelagic sequence, and turbidites resulted from the mixing of arc and accreted terranes. These data indicate that the source areas for the Galice Formation were already established by ca. 162 Ma, probably during a Middle Jurassic orogeny that predated formation of the Josephine basin.