Abstract The Paleocene–Eocene-aged Sele Formation is developed across the basinal region of the Central North Sea. The section comprises a number of deep-marine fan systems that expanded and contracted across the basin floor in response to relative sea-level changes on the basin margin and fluctuating sediment yield off the Scottish landmass modulated by climate and hinterland uplift. Persistent sediment entry points to the basin resulted in the development of discrete axial and transverse fan fairways with a geometry dictated by an irregular bathymetry sculpted by differential compaction across Mesozoic faults, halokinesis and antecedent fan systems. A high-resolution biostratigraphic framework has allowed the evolution of fan-dispersal systems in response to these effects to be tracked across the basin within four genetic sequences. The proximal parts of the fans comprised channel complexes of low sinuosity, high lateral offset, and low aggradation. The development of these systems in a bathymetrically confined corridor of the Central Graben ( c. 65 km wide), combined with high sediment supply, resulted in the eventual burial of any underlying relief. The behaviour of sand-rich reservoirs in this region is dominated by the permeability contrast between high-quality channel fairways and more heterolithic overbank regions, with the potential for early water breakthrough and aquifer coning in the channel fairways, and unswept volumes in overbank locations. Compartmentalization of compensationally stacked channel bodies occurs locally, with stratigraphic trapping caused by lateral channel pinch-outs, channel-base debrites, mud-rich drapes and abandonment fines. Towards the southern part of Quadrant 22, approximately 150 km down-palaeoflow, the systems became less confined and in this region are dominated by channel–lobe complexes, which continued to interact with an irregular bathymetry controlled by antecedent fans, mass-transport complexes and halokinesis in the form of rising salt diapirs. Reservoirs in this region are inherently stratigraphically compartmentalized by their heterolithic lithology and compensational stacking of lobes, and further complicated by structuration and instability induced by the diapiric or basement structures needed to generate a trapping structure in these settings.

Abstract The purpose of this field trip is to examine the sedimentology, sedimentary architecture, stacking patterns, and correlation of fluvial, coastal plain, deltaic, and shoreface to shelf deposits in the low accommodation Desert Member to Castlegate Sandstone stratigraphic interval (Campanian), Book Cliffs, eastern Utah. Traditional sequence stratigraphic models of falling stage deposits will be tested against an alternative sequence stratigraphic model that links the nonmarine to shallow-marine facies belts in both time and space. The trip will focus on the exceptional three-dimensional outcrop exposures in the Thompson Pass to Sagers Canyon region. At least eight sequence stratigraphic rock packages are identified and correlated, and these combine to form two progradational parasequence sets. The lower set comprises Desert Member rock packages 1-7, while the upper set comprises the SM/CC-2 rock package and overlying nonmarine strata of the Castlegate Sandstone. Rock package 7 is bounded above and below by coal-bearing, carbonaceous-rich zones. Correlation of the Upper and Lower Coal zones across the Crescent Canyon to Blaze Canyon region establishes a clear chronostratigraphic link between the nonmarine and shallow-marine strata of the Desert-Castlegate interval. The “fusing/welding” of rock packages 7 and SM/CC-2 with underlying cliff-forming sandstones in the South Face-Central to South Face-East region of Horse Heaven further demonstrates the chronostratigraphic link between the nonmarine and shallow marine. The alternative sequence stratigraphic interpretation of the Desert-Castlegate interval connects the nonmarine and shallow-marine facies belts in time and space, through correlation of coals, marine flooding surfaces, multi-storey channel complexes, and falling stage shallow-marine successions. “High-frequency” fluvial incision surfaces (sequence boundaries) merge to form a diachronous, lithostratigraphic contact between the nonmarine and shallow-marine facies belts. These contacts were previously defined as the “Desert SB” and “Castlegate SB” by J.C. Van Wagoner and were linked to longer term sea-level falls. Subsequent analysis of the “Desert SB” has revealed an amalgamation of “high-frequency” sequence boundaries that merge and split in a complex manner. Each “high-frequency” surface represents a shorter term portion of the longer term falling sea-level curve, which is equivalent to a parasequence-scale relative fall in sea level. “High-frequency” sequence boundary development, forced regression, and minor coastal plain aggradation occurs during the falling limb of the shorter term sea-level curve, followed by shallow-marine flooding, valley in-fill, coastal plain aggradation, and regional coal deposition during the rising limb of the shorter term sea-level curve. Individual nonmarine to shallow-marine chrono-slabs stack together. Inter-slab incision is rare in shallow-marine sections and where noted is relatively gentle (<3 m incision). In contrast, inter-slab incision is more significant in coastal plain settings due to reduced accommodation under falling stage conditions. The chrono-slab, parasequence-scale model for falling stage deposits in the Desert-Castlegate interval has four facies belts or zones. These record the transition from (i) nonmarine settings with single storey channels and scattered multistorey channel-fill complexes, to (ii) large-scale, multi-storey channel-fill successions (IVFs), to (iii) interbedded large-scale, multi-storey channel-fill successions (IVFs) and sandstone-rich proximal shallow-marine deposits, to (iv) proximal to distal, shoreface to shelf parasequences. This alternative chrono-slab model is likely applicable to falling stage deposits worldwide, especially those within a foreland basin setting. Ongoing research will extend the chrono-slab correlations outside of the study area and examine the relationship between relative sea-level history and chrono-slab thickness, facies belt length, and number of facies belts per chrono-slab.

Abstract Marine mudstone-encased, inner shelf sandstone bodies are concentrated in a 70–90-m-thick interval that spans the upper Aberdeen and lower Kenilworth members (Blackhawk Formation, Campanian), Book Cliffs, eastern Utah. These sandstone bodies contain a complex mixture of event beds including wave or storm-modi-fied turbidites, hummocky cross stratified sandstones, hyperpycnites, and/or classical turbidites. The turbiditic channel-fills and lobes were deposited below fair weather wave base and are detached from their time equivalent shoreface deposits. Shallow marine facies models should be revised to include turbiditic-rich channels and lobes in some inner shelf settings. A three-component shoreface-to-shelf model, consisting of delta front deposits, subaqueous channels, and prodelta turbidites, is proposed to explain the depositional setting and environment of the Mancos Shale–encased sandstone bodies. Oceanic- or river-flood induced hyperpycnal flows were responsible for cutting a network of subaqueous channels on the inner shelf and for transporting fine-grained sediments from the shoreface to the inner shelf. Other Mancos Shale–encased isolated sandstone bodies in eastern Utah and western Colorado should be reexamined in the light of the new data and models presented herein.