Hybrid event beds are texturally and compositionally-diverse deposits preserved within deepwater settings. They are deposited by flows exhibiting 'mixed behaviour', forming complex successions of sandstone and mudstone, which are often challenging to predict.Hybrid event beds are documented in deep-marine settings, where they have been thoroughly characterized, and are well-known as effective fluid transmissibility barriers and Accepted ArticleThis article is protected by copyright. All rights reserved baffles in reservoirs. By comparison, there are far-fewer studies of hybrid event beds from deep-lacustrine settings, where their character and distribution remains relatively underexplored. In order to provide insights into these deposits, this study presents the detailed analysis of three-dimensional seismic data, wireline logs and core from a series of ancient deep-lacustrine fan systems in the North Falkland Basin. Results confirm that deeplacustrine hybrid event beds comprise the same idealized sequence of the 'H1-H5' divisions.However, in this study H3 'debrite' units can be sub-divided into 'H3a-H3c', based on: sharp or erosional intra-H3 contacts, bulk lithology, mud-content and discrete sedimentary textures. This study interprets the H3a-H3c sub-units as the products of multiple flow components formed through significant rearward longitudinal flow transformation processes, during the emplacement of a single hybrid event bed. Hybrid event beds are observed within lobe fringes, where flow types, energies, and transport mechanisms diversify as a result of flow transformation. The temporal context of hybrid event bed occurrences is considered in relation to stages of fan evolution, including: the Initiation; Growth (I); Growth (II); By-pass; Abandonment; and Termination phases. Hybrid event beds are mainly found in either the initiation phase where flow interaction and erosion of initial substrates promoted mixed flow behaviour, or in the abandonment phase as facies belt retreated landward. The results of this study have important implications in terms of flow processes of hybrid event bed emplacement, in particular sub-division of the H3 unit, as well as the prediction of hybrid event bed occurrence and character within ancient deeplacustrine fan settings, in-general.

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Fault relay ramps are important sediment delivery points along rift margins and often provide persistent flow pathways in deepwater sedimentary basins. They form as tilted rock volumes between en-echelon fault segments, which become modified through progressive deformation, and may develop through-going faults that 'breach' the relay ramp. It is well established that hinterland drainage (fluvial/alluvial systems) is greatly affected by the presence of relay ramps at basin margins. However, the impact on deepwater (deep-marine/lacustrine) subaqueous sediment gravity flow processes, particularly by breached relay ramps, is less well documented. To better evaluate the complex geology of breached relay settings, this study examines a suite of high-quality subsurface data from the Early Cretaceous deep-lacustrine North Falkland Basin (NFB). The Isobel Embayment breached relay-ramp, an ideal example, formed during the syn-rift and was later covered by a thick transitional and early post-rift succession. Major transitional and early post-rift fan systems are observed to have consistently entered the basin at the breached relay location, directed through a significant palaeo-bathymetric low associated with the lower, abandoned ramp of the structure. More minor systems also entered the basin across the structure-bounding fault to the north. Reactivation of basin-bounding faults is shown by the introduction of new point sources along its extent. This study shows the prolonged influence of marginlocated relay ramps on sedimentary systems from syn-rift, transitional and into the early post-rift phase. It suggests that these structures can become reactivated during post-rift times, providing continued control on deposition and sourcing of overlying sedimentary systems. Importantly, breached relays exert control on fan distribution, characterised by laterally extensive lobes sourced by widespread feeder systems, and hanging walls settings by small-scale lobes, with small, often line-sourced feeders. Further characterising the likely sandstone distribution in these structurally complex settings is important as these systems often form attractive hydrocarbon reservoirs. EAGE PLENDERLEITH et al.

A significant knowledge gap exists when analysing and predicting the hydraulic behaviour of faults within carbonate reservoirs. To improve this, a large database of carbonate fault rock properties has been collected from 42 exposed faults, from 7 countries. Faults analysed cut a range of lithofacies, tectonic histories, burial depths and displacements. Porosity and permeability measurements from c.400 samples have been made, with the goal of identifying key controls on the flow properties of fault rocks in carbonates. Intrinsic and extrinsic factors have been examined, such as host lithofacies, juxtaposition, host porosity and permeability, tectonic regime, displacement, maximum burial depth as well as the depth at the time of faulting. The results indicate which factors may have the most significant influence on fault rock permeability, improving our ability to predict the sealing or baffle behaviour of faults in carbonate reservoirs. Intrinsic factors, such as host porosity, permeability and texture, appear to play the most important role in fault rock development. Extrinsic factors, such as displacement and kinematics, have shown lesser or, in some instances, a negligible control on fault rock development. This conclusion is, however, subject to two research limitations: lack of sufficient data from similar lithofacies at different displacements, and a low number of samples from thrust regimes.Thematic collection: This article is part of the Fault and top seals collection available at: https://www.lyellcollection.org/cc/fault-and-top-seals-2019