Abstract Petroleum geochemistry has historically relied on the analysis of field samples – source rocks, oils and gases. Data collected for individual samples are considered characteristic of a specific geographical location and geological position that, when aggregated with data from other samples, can be extrapolated to larger scales. These scale-ups may be as small as a few metres, such as a detailed characterization of source rocks penetrated by a single well, to global, such as petroleum systems that now span continents due to plate tectonics. However, a single sample contains a wealth of information at smaller scales. In situ analytical techniques have improved significantly over the last decade, allowing us to examine sedimentary rocks at ever higher spatial (areal and temporal) resolution. Mass spectrometric imaging is an emerging, enabling technology that can be performed at c. 200 µm (matrix-assisted laser desorption) to 50 nm (nanoSIMS) resolution. X-ray microcomputed tomography (µ-CT) is being applied to examine the storage and transport of petroleum in low-permeability shales and carbonates at spatial resolutions as low as c. 8 µm. Pore architecture in shale, both organic and inorganic, can be modelled from small-angle neutron scattering (SANS) data and imaged directly with helium ion microscopy at c. 1 nm resolution. Atomic force microscopy (AFM) can now resolve the molecular structure of individual asphaltene molecules. Information obtained with these techniques is now revealing the fundamental nature of geological organic materials, opening the span of petroleum geochemistry from atoms to continents.

ABSTRACT The Alikayasi canyon–channel system of the Miocene Maras Basin, eastern Turkey, is compared with the South Brae fan, South Viking Graben, United Kingdom sector, North Sea, demonstrating the importance of outcrop analogs to subsurface oil reservoirs. The Alikayasi canyon–channel is a coarse-grained, deep-water slope depositional system that developed in a contractional tectonic setting south of a large continental landmass. Sediment was fed through large, stable river systems and fan deltas, across a relatively narrow continental shelf, through gullies directly into the head of the slope system. Coarse sediment supply at Alikayasi was continuous, but periodic increases in tectonism caused increases in depositional slope, and hence canyon-cutting. First-order erosional surfaces mark such pulsed reactivation of the canyon–channel complex system. During slope steepening, canyon reincision took place, with sediment bypass downdip to the south. Backfilling of the canyon–channel complex system, alternating with pulses of sediment bypass, occurred during periods of more stable tectonic conditions, where the development of channel–overbank systems with aggradational channel levee elements is recognized. The South Brae fan is a coarse-grained, channelized lower base-of-slope system that developed in an extensional setting outboard of a relatively small landmass to the west and northwest. In the earlier, most active phase of rifting, high relief developed on the footwall and supply of coarse sediment was more or less continuous to the graben-margin trough, resulting in thick conglomeratic sections that lie beneath the South Brae reservoir. In later phases, as the graben-margin trough filled and the relief on the footwall decreased, deposition of gravels and sands in channels was more pronounced, muds were deposited close to channel systems, and sand deposition extended into the basin. Periodic interruptions in coarse sediment supply for substantial time periods led to deposition of field-wide muds. Coarse sediment supply then resumed, probably as a result of renewed tectonic activity that uplifted the footwall, initially resulting in down-cutting into the field-wide mudstone and bypass of sand into the basin. This was followed by backfilling of developing channels with gravel and sand and the development of interchannel muddy levees. Despite some differences in scale, channel systems at South Brae resemble canyon and channel complex systems like the Turkish Maras Basin examples. South Brae channel bases are erosional, at least in the thalwegs, as are the bases of Alikayasi channel complexes. Channel to channel-margin facies sequences at South Brae resemble to some extent channel fill–overbank sequences at Alikayasi. This is the main area where more detailed study of the geometric relationships between exposed channel fills and overbank deposits at Alikayasi might lead to revised interpretation of depositionally related units at South Brae, and hence aid more accurate reservoir mapping.