The effects of downstream base-level control on fluvial architecture and geometry are well explored in several broadly similar sequence-stratigraphic models. Cretaceous Dakota Group strata, U.S. Western Interior, have characteristics reflecting combined downstream and upstream base-level controls that these models cannot address. Particularly, three layers of amalgamated channel-belt sandstone within this group thicken and are continuous for distances (# 300 km) along dip that stretch the reasonable lengths for which these models are intended to apply. As well, architecture in up-dip reaches records repeated valley-scale cut-and-fill cycles. This contrasts with equivalent strata down dip which record channel-scale lateral migration with no such valley-scale cycles apparent.We here introduce the concept of ''buffers and buttresses'' to address these observations. We assume that river longitudinal profiles are each anchored down dip to some physical barrier (e.g., the sea strand, etc.) that we refer to as a ''buttress.'' Buttress shift is considered the primary downstream control on base level. Profiles extrapolated up dip from the buttress over any modeled duration of buttress shift can range widely because of high-frequency variability in upstream base-level controls (e.g., discharge, etc.). All these potential profiles however are bounded above by the profile of highest possible aggradation, and below by the profile of maximum possible incision. These upper and lower profiles are ''buffers,'' and they envelop the available fluvial preservation space. Thickness of the buffer zone is determined by variability in upstream controls and should increase up dip to the limit of downstream profile dominance. Dakota valley-scale surfaces record repeated cut-and-fill cycles driven by up-dip controls and are confined between thick stable buffers. Equivalent strata down dip record lateral reworking within a thinner channel-scale buffer zone that was positioned by downstream controls. Regression exposed slopes similar to the buffer zone, thus buffers were stable for long distances and durations. This prompted dip-extensive lateral reworking of strata into upstream valley-scale and downstream channel-scale sheets.Buffers and buttresses provide a broadly applicable model for fluvial preservation that captures upstream vs. downstream base-level controls on geometry and architecture. The model lends general insights into dip-oriented variations in fluvial architecture, production of sheet vs. lens geometry, total preservation volumes for fluvial systems, and variations in these factors related to contrasting climatic conditions and basin physiography. The model can be amended to existing sequence stratigraphic approaches in order to capture dip-oriented variations in sequence architecture.

No abstract

Carbonate deposits dominated the southeastern part of the Arabian Shelf from Berriasian to Santonian time, approximately 60 Ma. Deposition was terminated by the development of the Oman Foredeep in Coniacian-Santonian following the initial emplacement of the Hawasina and Semail nappes in the Turonian. The Lower and middle Cretaceous units in Arabia correlate with European reference sections and the current ages of the stage boundaries can be used to form a quantitative scale.The Thamama-Kahmah Group to the Ilam-Halul Limestone consists of four major unconformity-bounded, shoaling-up depositional sequences that range in duration from 3 to 22 Ma. These sequences represent significant transgressive events on the shelf. The

A high‐energy Aptian–Albian platform margin in northern Oman fronted onto an open oceanic basin, making the area a valuable analogue for coeval guyot margins. Most similar aged carbonate margins described in the literature faced either intracratonic or minor oceanic basins. The studied margin is characterized by a stabilized outer rim, which, although it did not rise discernibly above the adjacent lagoonal deposits, flanked a steep upper slope (32–40°) basinwards with a relief of at least 30 m. Two main facies provided the rigidity of the outer margin: Lithocodium boundstones that constituted up to 50% of the rock volume; and marine fibrous cements that occluded up to 35% of primary pore space. In contrast, coral–rudist patches and other shelly sessile benthos were distributed irregularly, and the rudist bioherms of the outer margin were often disrupted, with shells being transported and redeposited. The inner margin is characterized by wedge‐shaped storm layers that radiate from the platform top lagoonwards, where they interdigitate with carbonate sands and small rudist bioherms. Polygenetic discontinuity surfaces that bear evidence of both marine hardground and subaerial exposure stages are prominent features of the margin. Throughout the latest Aptian to Middle Albian, the platform succession recorded some 30 relative sea‐level falls, of which seven reached amplitudes of many tens of metres. These seven high‐amplitude falls in sea level are recorded across the entire south‐eastern portion of the Arabian craton and are probably of eustatic origin.

Photodynamic therapy simultaneously reduces plaque inflammation and promotes repopulation of plaques with a SMC-rich stable plaque cell phenotype while reducing disease progression. These early healing responses suggest that PDT is a promising therapy for the treatment of acute coronary syndromes.

No abstract

No abstract

No abstract