Predicting Coastal Depositional Style: Influence of Basin Morphology and Accommodation To Sediment Supply Ratio Within A Sequence Stratigraphic Framework

Author(s):  
R. BRUCE AINSWORTH ◽  
STEPHEN S. FLINT ◽  
JOHN A. HOWELL
2020 ◽  
Vol 57 (11) ◽  
pp. 1289-1304
Author(s):  
Brandon M. Keough ◽  
Olivia A. King ◽  
Matthew R. Stimson ◽  
Page C. Quinton ◽  
Michael C. Rygel

The Maritimes Basin of Atlantic Canada contains a rich record of Pennsylvanian cyclothems. Previous studies have focused on rapidly subsiding depocenters in the central part of the basin where Carboniferous successions feature cyclic alternations between terrestrial and marginal marine strata. In contrast, the Pennsylvanian Clifton Formation was deposited on the relatively stable New Brunswick platform and contains almost entirely terrestrial strata. Although early studies of the Clifton Formation noted a cyclic architecture, particularly within Member B, this unit has remained understudied. We provide a sedimentological and sequence stratigraphic framework for the lower 85 m of Member B and interpret our results relative to a broader regional framework. Near the base of the study interval, the highstand systems tract is composed of red floodplain mudrocks; overlying sequence boundaries are composed of calcretes and (or) channels. The transgressive systems tract and maximum flooding surface are represented by coals and aquatic bivalve-bearing mudrocks. Moving upward through the section, the architecture of the highstand systems tract remains largely unchanged while sequence-bounding paleosols become less well developed, the transgressive systems tract becomes thinner and eventually not preserved, and the maximum flooding surface is only occasionally preserved, possibly represented by carbonaceous shales. These changes in cyclic architecture may be attributed to changes in the magnitude of glacioeustatic fluctuations, climate, and (or) the accommodation/sediment supply ratio. The results of this study show that the Clifton Formation represents the terrestrial/proximal endmember for cyclicity in the Maritimes Basin and provide new insight into paleotopography as a possible control on cyclothem architecture.


1998 ◽  
Vol 38 (2) ◽  
pp. 132
Author(s):  
I.A. Dyson

Greensand reservoirs are particularly significant in siliciclastic shoreline systems. Formation of autochthonous glauconite is restricted almost exclusively to the rising limb of the relative sea level (RSL) curve. Depositional environments that are typically developed in response to a rise in RSL are estuaries, barrier bars and shoreface sands. In this setting, the greensands are diachronous and exploration for hydrocarbon reservoirs should ideally be based on a sequence stratigraphic framework. These deposits are characterised by a number of significant surfaces that differ greatly in their origin, geographic extent and chronostratigraphic significance, and their thickness depends on the rate of RSL rise and sediment supply. The identification of significant surfaces bounding or contained within depositional sequences is critical, especially where drillhole samples are either unreliable or not available for geochemical and palynological analysis. Abrupt physical and chemical changes often occur on or across these surfaces, e.g. porosity, permeability and the presence of Fe-rich authigenic minerals such as glauconite and siderite. Greensands deposited in estuarine, barrier bar and shoreforce environments have excellent oil and gas potentail. Early Cretaceous greensand reservoirs from the North West Shelf are best developed where they overlie ravinement surfaces. Recognition of greensands within estuarine, barrier bar and shoreface environments is dependent on the correct identification of facies and the subsequent interpretation of the bounding discontinuities.


GeoArabia ◽  
2010 ◽  
Vol 15 (2) ◽  
pp. 91-156 ◽  
Author(s):  
Bastian Koehrer ◽  
Michael Zeller ◽  
Thomas Aigner ◽  
Michael Poeppelreiter ◽  
Paul Milroy ◽  
...  

ABSTRACT The Middle Permian to Lower Triassic Khuff Formation is one of the most important reservoir intervals in the Middle East. This study presents a sequence stratigraphic analysis of the Khuff Formation of a well-exposed outcrop in the Oman Mountains, which may provide a reference section for correlations across the entire Middle East. On the Saiq Plateau of the Al Jabal al-Akhdar, the Permian Upper Saiq Formation is time-equivalent to the Lower and Middle Khuff Formation (K5–K3 reservoir units in Oman). The Permian section is dominated by graded skeletal and peloidal packstones and cross-bedded grainstones with a diverse marine fauna. The Lower Mahil Member (Induan Stage), time-equivalent to the Upper Khuff Formation (K2–K1 reservoir units in Oman), is dominated by grainstones composed of microbially-coated intra-clasts and ooids. In general, the studied outcrop is characterized by a very high percentage of grain-dominated textures representing storm-dominated shoal to foreshoal deposits of a paleogeographically more distal portion of the Khuff carbonate ramp. A sequence-stratigraphic analysis was carried out by integrating lithostratigraphic marker beds, facies cycles, bio- and chemostratigraphy. The investigated outcrop section was subdivided into six third-order sequences, named KS 6 to KS 1. KS 6–KS 5 are interpreted to correspond to the Murgabian to Midian (ca. Wordian to Capitanian) stages. KS 4-Lower KS 2 correspond to the Dzhulfian (Wuchiapingian) to Dorashamian (Changhsingian) stages. Upper KS 2–KS 1 represent the Triassic Induan stage. Each of the six sequences was further subdivided into fourth-order cycle sets and fifth-order cycles. The documentation of this outcrop may contribute to a better regional understanding of the Khuff Formation on the Arabian Platform.


2017 ◽  
Vol 4 (1) ◽  
pp. 85 ◽  
Author(s):  
Zhipeng Lin ◽  
Le Chen ◽  
Jingfu Shan ◽  
Tan Zhang ◽  
Qianjun Sun ◽  
...  

Currently, the recognition and research on the classification of fluvial types mainly focus on the description and results of a series of indicators, such as the plane shape and sediment characteristics. However, there is limited literacy about how to demonstrate the fluvial types from the depositional process, especially less on sequence model of inland fluvial. Thus, this paper aims o propose a new kind of sequence stratigraphic framework, which is able to reflect the fluvial processes under the perspective of sequence stratigraphy. Accordingly, we use the principle of concrete analysis for concrete problems by comprehensively summing up the previous classification schemes of river types. With the research method of sedimentation process, new fluvial systems tracts for fluvial are presented here, including four parts: low fluvial system tract (LFST), advancing fluvial system tract (AFST), flooding fluvial system tract (FFST), receding fluvial system tract (RFST). Moreover, these could be applied to tackle the problem of the traditional division of fluvial. Various rivers have the different characteristics of systems tracts, then this may play a vital role in the discrimination of meandering river, braided river, anastomosing river and branched river. This study embodies the philosophical thought of Process Sedimentology and may contribute to revealing the deposition process of the fluvial system more profoundly from the aspect of genetic mechanism and evolution course. Most importantly, the fluvial classification system is definitely improved from the description stage to a complete rational stage.


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