This study documents the character and occurrence of hybrid event beds deposited across a range of deep-water sub-environments in the Cretaceous-Palaeocene Gottero system, north-west Italy. Detailed fieldwork (>5200 m of sedimentary logs) has shown that hybrid event beds are most abundant in the distal confined basin plain domain (>31% of total thickness). In more proximal sectors, HEBs occur within outer-fan and mid-fan lobes (up to 15% of total thickness), whereas they are not observed in the inner-fan channelised area. Six hybrid event bed types (HEB-1 to HEB-6) were differentiated mainly on basis of the texture of their muddier and chaotic central division (H3). The confined basin plain sector is dominated by thick (max 9.57 m; average 2.15 m) and tabular hybrid event beds (HEB-1 to HEB-4). Their H3 division can include very large substrate slabs, evidence of extensive auto-injection and clast break-up, and abundant mudstone clasts set in a sandy matrix (dispersed clay ca 20%). These beds are thought to have been generated by highly This article is protected by copyright. All rights reserved.energetic flows capable of delaminating the sea-floor locally, and carrying large rip-up clasts for relatively short distances before arresting. The unconfined lobes of the mid-fan sector are dominated by thinner (average 0.38 m) hybrid event beds . Their H3 divisions are characterised by floating mudstone clasts and clay-enriched matrices (dispersed clay >25%) with hydraulically-fractionated components (mica, organic matter and clay flocs). These hybrid event beds are thought to have been deposited by less energetic flows that underwent early turbulence damping following incorporation of mud at proximal locations and by segregation during transport. Although there is a tendency to look to external factors to account for hybrid event bed development, systems like the Gottero imply that intrabasinal factors can also be important; specifically the type of substrate available (muddy or sandy) and where and how erosion is achieved across the system producing specific hybrid event bed expressions and facies tracts. (A) INTRODUCTIONBed character and bed stack architecture are two key elements controlling the heterogeneity of deep-water turbidite systems. The former represents the depositional record of sediment gravity flows at a given location with the vertical sequence of grain-size, textures and sedimentary structures recording flow evolution in time and space (Bouma, 1962; Lowe, 1982; Mutti, 1992; Kneller, 1995; Kneller & McCaffrey, 2003). The latter is set by the longer term response of the system to variations in flow volume and concentration over many events modulated by the inherited seafloor topography (Prélat et al., 2010; Brunt et al., 2013b; Marini et al., 2015a). Both define the character and distribution of sedimentary sub-environments in deep-water systems.A wide range of sediment gravity flow deposits have been recognised in turbidite systems; they include the well-known Bouma-type graded sandstones an...

Turbidity currents, and other types of submarine sediment density flow, redistribute more sediment across the surface of the Earth than any other sediment flow process, yet their sediment concentration has never been measured directly in the deep ocean. The deposits of these flows are of societal importance as imperfect records of past earthquakes and tsunamogenic landslides and as the reservoir rocks for many deep-water petroleum accumulations. Key future research directions on these flows and their deposits were identified at an informal workshop in September 2013. This contribution summarizes conclusions from that workshop, and engages the wider community in this debate. International efforts are needed for an initiative to monitor and understand a series of test sites where flows occur frequently, which needs coordination to optimize sharing of equipment and interpretation of data. Direct monitoring observations should be combined with cores and seismic data to link flow and deposit character, whilst experimental and numerical models play a key role in understanding field observations. Such an initiative may be timely and feasible, due to recent technological advances in monitoring sensors, moorings, and autonomous data recovery. This is illustrated here by recently collected data from the Squamish River delta, Monterey Canyon, Congo Canyon, and offshore SE Taiwan. A series of other key topics are then highlighted. Theoretical considerations suggest that supercritical flows may often occur on gradients of greater than , 0.6u. Trains of up-slope-migrating bedforms have recently been mapped in a wide range of marine and freshwater settings. They may result from repeated hydraulic jumps in supercritical flows, and dense (greater than approximately 10% volume) near-bed layers may need to be invoked to explain transport of heavy (25 to 1,000 kg) blocks. Future work needs to understand how sediment is transported in these bedforms, the internal structure and preservation potential of their deposits, and their use in facies prediction. Turbulence damping may be widespread and commonplace in submarine sediment density flows, particularly as flows decelerate, because it can occur at low (, 0.1%) volume concentrations. This could have important implications for flow evolution and deposit geometries. Better quantitative constraints are needed on what controls flow capacity and competence, together with improved constraints on bed erosion and sediment resuspension. Recent advances in understanding dilute or mainly saline flows in submarine channels should be extended to explore how flow behavior changes as sediment concentrations increase. The petroleum industry requires predictive models of longer-term channel system behavior and resulting deposit architecture, and for these purposes it is important to distinguish between geomorphic and stratigraphic surfaces

10The outer parts of deep-water fans, and the basin plains into which they pass, are often described as 11 areas where erosion is negligible and turbidite systems have net aggradation. Nevertheless 12 sedimentological and stratigraphic analysis of outer fan lobe and confined basin plain deposits in 13Cretaceous-Paleocene Gottero Sandstone (NW of Italy) has revealed extensive but cryptic bedding-14 parallel substrate-delamination features at the base of many sheet-like event beds. These comprise well layered substrate (e.g. muddy outer fans or confined or ponded basins with thick mudstone 25 caps). Delamination is therefore suggested as an alternative mechanism leading to the formation of 26 hybrid event beds following local substrate entrainment on the basin floor as opposed to on more 27 remote slopes and at channel-lobe transition zones. 28

Please cite this article as: Fonnesu, M., Haughton, P., Felletti, F., McCaffrey, W., Short length-scale variability of hybrid event beds and its applied significance, Marine and Petroleum Geology (2015), doi: 10.1016/j.marpetgeo.2015.03.028. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Understanding the transformations of the climate system may help to predict and reduce the effects of global climate change. The geological record provides a unique archive that documents the long-term fluctuations of environmental variables, such as seasonal change. Here, we investigate how seasonal variation in seawater temperatures varied in the Mediterranean Sea during the early Pleistocene, approaching the Early-Middle Pleistocene Transition (EMPT) and the beginning of precession-driven Quaternary-style glacial-interglacial cycles. We performed whole-shell and sclerochemical stable isotope analyses (δ 18 O, δ 13 C) on bivalves, collected from