Abstract Stratal stacking patterns and platform distribution within the Devonian Beaverhill Lake Sequence of northern Alberta were influenced by several factors, those that were primarily external (e.g., climate change, trade-wind flow, terrigenous mud supply) and those that were internal (e.g., carbonate factory, water circulation, basin topography). Within the first-rank Beaverhill Lake Sequence, our study revealed two second-rank (1,2) and 10 third-rank (A-J) transgressive-regressive (T-R) sequences within the Beaverhill Lake Sequence, many of which were progradational and basin-filling, even during a relative rise in sea level. Furthermore, our study reveals three distinct phases of sedimentation during the depositional interval. The first phase of sedimentation occurred during T-R sequence A. During the initial sea-level rise of sequence A, the Peace River Arch fringing platform and Hay River platform initiated along the western margin of the study area. Platforms aggraded, but they did not prograde significantly, likely because detrital carbonate sediment was transported by surface currents into the inner platform and because of the proximity of the platforms to a limited but adequate supply of nutrients. The condensed limestone across the shallow Waterways Subbasin at the end of sequence A was produced by a local carbonate factory within or near the base of the photic zone, but under nutrient-starved conditions. Slope environments near the platforms contained a mixture of locally produced carbonate sediment and transported allochems. Therefore, this first phase of sedimentation during the Beaverhill Lake Sequence contains circulation-and nutrient-constrained carbonate platforms on the western side of the study area and limited carbonate accumulation within a shallow basin. Mixing of sediments between the two environments occurred only within slope deposits. The second phase of sedimentation occurred during the clinoformal infilling of the Waterways Subbasin with the progradation of the carbonate-siliciclastic Eastern Platform, the drowning and burial of the Hay River platform, and the back stepping of the Peace River Arch fringing platform. Lithofacies and faunas found on the Eastern Platform generally grade into deeper-water components, often by the increase in argillaceous sediment in carbonate beds and the loss of shallow-water organisms. Basinal sediments are mainly argillaceous in the thin toes of the clinoforms in the Waterways Subbasin. Evidence of sediment transport by gravity flow or other mechanisms from the Eastern Platform down the slope and into the basin is rare in core and restricted to occasional tempestite-like beds and individual allochems derived from shallow-water organisms. Although the transport of micrite basinward by water currents is likely to have occurred, an in situ fauna inhabited at least the upper portion of the slope environment and produced carbonate sediment. The third and final phase of sedimentation in the Beaverhill Lake Sequence was generally aggradational, with a much-reduced difference in topography between the Eastern Platform and the Waterways Subbasin. Lithofacies and faunas found on the Eastern Platform can be traced into the Waterways Subbasin. Faunas change little, but lithofacies tend to become more argillaceous throughout the study area. The definition of the Eastern Platform margin can only be seen in cross section where carbonates thin abruptly westward.

Abstract Over the past 20 yr, the concept of storing or permanently storing (i.e., sequestering) carbon dioxide (CO 2 ) in geological media has gained increasing attention as part of the important technology option of carbon capture and storage (CCS) within a portfolio of options aimed at reducing anthropogenic emissions of greenhouse gases to the earth’s atmosphere (International Energy Agency [IΕΑ], 2004 , 2008 ; Pacala and Socolow, 2004 ; Intergovernmental Panel on Climate Change [IPCC], 2005 , 2007 ; Socolow, 2005 ; Balat and Öz, 2007 ; Bryant, 2007 ; National Energy Technology Laboratory [NETL], 2008 ). Research programs focusing on the establishment of field demonstration projects are being implemented worldwide to investigate the safety, feasibility, and permanence of CO 2 geological sequestration. The number of potential geological sinks for sequestration of CO 2 , such as depleted oil and gas reservoirs, deep-saline reservoirs (brine-filled formations), and deep, unmineable coalbeds, is shrinking. The technology to use these sinks is in various phases of applicability and implementation, with CO 2 sequestration in enhanced oil recovery being the most mature and economically feasible and CO 2 sequestration in coal beds in conjunction with enhanced coalbed methane recovery being still in the demonstration phase. Currently, the most significant barrier to the implementation of geological sequestration lies in the high cost of CO 2 capture, but major challenges also still exist in defining and identifying sinks with the necessary capacity in proximity to major CO 2 sources as well as identifying, mitigating, and remediating