Abstract The Lower Jurassic Cook Formation reservoir is a hydrocarbon-prolific unit that produces from several fields in the northern North Sea. For 40 years this formation has been interpreted as a westward-prograding deltaic unit sourced from Norway. Despite numerous discoveries, exploration targeting this unit has been hampered by well failures with lack of reservoir sand, discouraging companies from further exploration of this play. During a current re-evaluation of the process sedimentology of the Norwegian offshore basins, the Cook Formation is now interpreted as the middle to distal reaches of a very large, north-to-south-oriented delta system, variably confined within the Early Jurassic Seaway running from the Norwegian Sea into the northern North Sea. The Cook Formation is a subaqueous delta built southward during regression, whereas several internal transgressive phases produced sands that were reworked as north–south-oriented, shelf tidal ridges. The tidal ridges of the Cook Formation constitute some of the best reservoirs and are elongated with stacked, well-sorted, cross-bedded sandstone sets with mudstone drapes. Both the elongate tidal sand-ridges and intervening mudstone-rich, inter-ridge zones are proven by numerous well observations and illustrated by seismic amplitudes. In contrast to earlier eastern derivation models, these new results for the depositional system of the Cook Formation better explain the Cook well successes and failures in the northern North Sea. This work also strongly suggests that the tide-dominated subaqueous delta to transgressive-ridge system of the Cook Formation is spatially linked with the time-equivalent shorelines, subaerial tidal deltas and estuaries of the Tilje Formation in the Haltenbanken region to the north. The Tilje Formation deltas built into the Early Jurassic Seaway due to rift-initiation and rift-shoulder uplift, drained southwards and spilled eventually into the northern North Sea, becoming the entirely subaqueous Cook Formation. The relatively narrow seaway enhanced the tidal currents and suppressed wave activity, resulting in Cook subaqueous delta lobes and ridges without any delta-top facies. Overall, this elongate and extensive, Pliensbachian deltaic to estuarine system of the Early Jurassic Seaway off Norway competes in scale with some of Earth's largest present-day deltas.

Abstract Two outcrops of the Bremen Sandstone are located on or near River Highway, 2.4 mi (3.9 km) north of Alabama 69, in Sec.l, T.13S, R.6W, and Sec.6, T.13S, R.5W, Walker County, Alabama, on the Lewis Smith Lake Dam 7½-minute Quadrangle.

Abstract: Deltas represent the major sediment source for tectonically confined, tide-dominated seaways or straits. Modern examples show how along-shore tidal currents are able to modify the impinging delta shape, generating asymmetrical coastal plains, deflected delta fronts and elongate sandbanks. Seaway or strait deltas can become become tide-influenced or tide-dominated, assuming physical attributes that may depart from classical models. Ancient deltas in seaways and straits can also reveal unexpected facies stacking and stratigraphies, which can be misinterpreted or attributed to different depositional settings. Two ancient analogues of deltas that prograded into elongate basins dominated by amplified tidal currents are presented here. A common element in these deltas is the progressive-upwards change in the dominant process of sediment dispersion recorded in the delta facies. Early stages of progradation are dominated by river- and wave-influenced lithofacies, whereas late deltaic advancements occur with a dominance of tidal current circulation on the delta fronts and the consequent morphologies are deflected/elongated in the direction of tidal flow. This study provides the basis for a preliminary stratigraphic framework for the depositional style of these types of delta. The studied deposits also suggest analogies with the spatial distribution of many hydrocarbon reservoirs investigated along the margins of confined, narrow, linear basins, the interpretation of which is still debated.