Sedimentology and ichnology of the Lower Triassic Montney Formation in the Pedigree-Ring/Border-Kahntah River area, northwestern Alberta and northeastern British Columbia (original) (raw)
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International Journal of Coal Geology, 2015
This study summarizes the results of petrographic and geochemical analysis of Middle Triassic strata from the Sverdrup Basin in the Canadian Arctic. In this work, we investigate the distribution and depositional conditions of dispersed organic matter (OM) as a preliminary step towards understanding the potential of this stratigraphic interval as an unconventional reservoir. Closely-spaced samples from three Middle Triassic cores (southern margin, basin centre, northern margin) are analyzed using Rock-Eval analysis, inductively coupled plasma-mass spectrometry (ICP-MS), and organic petrology. Total organic carbon (TOC) ranges between 0 and 4.8 wt.%, with the most organic-rich interval having a median TOC value of 3.2 wt.%. Kerogen type varies from Type II to Type III throughout the sampled intervals. Samples from near the top of the regressive systems tract of the Anisian 3rd order sequence (basin centre) and near the middle of the Ladinian 3rd order sequence (southern margin) contain predominantly reworked, highly oxidized macerals and abundant coarser clastic material. Results support oxic to suboxic depositional conditions for these intervals. By contrast, samples from near the base of regressive systems tracts of both sequences (basin centre and northern margin) have the highest amounts of TOC (i.e., median = 3.2 wt.% and 1.4 wt.%), containing retained migrabitumen and abundant labile primary kerogen, respectively. The base of the Ladinian regressive systems tract near the basin axis was deposited under anoxic conditions and can be considered a prospective shale oil interval. Small-scale cyclic clastic influx episodes along the northern margin of the basin show changes from oxic to suboxic bottom waters. These cycles may be considered evidence for northerly-derived sediment from Crockerland during the Middle Triassic. The results and interpretations of this study can be applied to analogous fine-grained successions in other basins to better understand their unconventional reservoir potential.
Foreword -- Marine Conglomerate Reservoirs: Cretaceous of Western Canada and Modern Analogues
Bulletin of Canadian Petroleum Geology, 2004
This two-part special issue of the Bulletin of Canadian Petroleum Geology evolved from a technical session on "Marine Conglomerate Reservoirs" at the 2002 CSPG Diamond Jubilee Convention. The session was highlighted by eight oral and three poster presentations, seven of which formed the basis for manuscript contributions. The intent of the original technical session, as well as this subsequent special two-part publication, was to assemble a collection of targeted presentations covering a spectrum of topics relevant to hydrocarbon exploration in conglomerate reservoirs of marine origin in the Western Canada Sedimentary Basin. The majority of these conglomeratic units are natural gas reservoirs that comprise the backbone of the Deep Basin's productivity, and include some of the most prolific gas horizons in all of western Canada. From a global perspective, reservoirs of this geological nature and origin are relatively unique, if not rare. However, they are not uncommon in the Cretaceous of Alberta and British Columbia. Some, such as the Cardium and Viking formations, have been the focus of numerous studies, geological investigations and exploration drilling. However, for those conglomerate reservoirs of shallow marine origin within the Deep Basin, there has been little published work made available since the landmark AAPG Memoir 38 publication of Masters (1984). This lack of current information in the public domain, coupled with the recent completion of several relevant University theses and industry funded geological investigations, provided the impetus for the editors to compile these publications. This two-part publication was designed to be broad in its scope, and as such provides a multidisciplinary approach to the investigation and prediction of shallow marine conglomerate reservoir facies. Topics range from sedimentary processes and geomorphology of modern day graveliferous shorelines to the sedimentological, stratigraphic and ichnological analyses of conglomerates in outcrop and subsurface. Of greatest and most immediate practicality to the geoscientist involved in the exploration of conglomerate reservoirs, are the regional subsurface investigations of natural gas bearing horizons from the Deep Basin. However, we remind our industry colleagues that while time is almost always of the essence in the oil and gas business, the non-immediately applied investigations published in this two-part publication, or any other of a similar bent, provide the building blocks and tools to understanding the internal architecture and prediction of conglomerate reservoirs in general. It is for these reasons, that these publications provides a collection of both recent results from University research and industry work as well as summary articles of investigations of gravel and conglomerates of shallow marine origin. For reasons of efficiency and cost, the special publication has been divided into part one (December, 2003) and part two (March, 2004). The two-part publication includes fivetopical headings discussed below. MODERN DEPOSITIONAL ENVIRONMENTS AND ANALOGUES Shallow marine conglomerate is a unique, if not rare, sedimentary deposit in the geological record. It is however of significant economic and scientific importance. Recognizing this as a premise, Clifton introduces this topic with an examination of the specific conditions of supply, transport and concentration of gravel accumulations as the precursor to conglomerate deposits. Unlike their finer-grained counterparts within the spectrum of clastic sediments, gravel and/or conglomerate deposits are poorly understood and relatively under-studied. This is principally due to the logistical difficulties in coring, trenching and otherwise observing the preserved fabrics of gravel accumulations in modern environments. In addition, within the realm of process sedimentology, almost all understanding and knowledge of clastic sediment transport and formation of bedforms and structures has been observed through experimentation in the sand faction, not gravel. Thus, Clifton examines the issues of supply, segregation and succession of shallow marine gravels through his observations of the stratigraphic record. As a pioneer, and recognized authority in this field, Clifton provides several examples of detailed sedimentological and stratigraphic analyses of shallow marine conglomerates from the tectonically active margin of the northwestern United States.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2012
In spite of the high interest on the Late Devonian-Early Carboniferous Bakken Formation as one of the most important oil plays in North America and the numerous studies carried out in this unit, no ichnologic analysis has been presented yet. Based on conventional sedimentologic data, previous studies of the Bakken interpreted the unit as formed entirely under open-marine conditions. However, integration of ichnology has been key to the identification of not only open-marine but also brackish-water marginal-marine conditions. Based on the geometry of the sedimentary bodies and the sequence-stratigraphic framework, the brackishwater interval is interpreted as an embayment with limited or intermittent connection to the open sea. Salinity, oxygen content, and storms are regarded as the most important environmental parameters that controlled the distribution and nature of the trace fossils in the Bakken Formation. Sparse bioturbation, relatively low ichnodiversity, and the "impoverished" Cruziana ichnofacies characterize the marginalmarine deposits, suggesting stressful brackish-water conditions. Marine deposits from the middle member, in contrast, are highly bioturbated, with a moderate ichnodiversity and the "distal" Cruziana ichnofacies that flourished during fully marine well-oxygenated conditions. There is only a slight difference between the total ichnodiversity of the open-marine interval (ten ichnogenera) and that of the brackish-water interval (seven ichnogenera). Ichnodiversity should not be considered at face value and isolated from other aspects when evaluating stress levels in order to detect a brackish-water signal. Lack of bioturbation in the black shale of the lower and upper members resulted from anoxic conditions. The passage from anoxic (lower member) to well-oxygenated conditions (middle member) was gradational, as is revealed by the occurrence of oxygen-deficient trace-fossils at the top of the lower member. Finally, the contrasting styles in tempestite preservation in upper-offshore deposits from the lower and upper open-marine intervals is attributed to variations in the intensity and frequency of storm during deposition of the highstand and transgressive deposits.
In spite of the high interest on the Late Devonian-Early Carboniferous Bakken Formation as one of the most important oil plays in North America and the numerous studies carried out in this unit, no ichnologic analysis has been presented yet. Based on conventional sedimentologic data, previous studies of the Bakken interpreted the unit as formed entirely under open-marine conditions. However, integration of ichnology has been key to the identification of not only open-marine but also brackish-water marginal-marine conditions. Based on the geometry of the sedimentary bodies and the sequence-stratigraphic framework, the brackishwater interval is interpreted as an embayment with limited or intermittent connection to the open sea. Salinity, oxygen content, and storms are regarded as the most important environmental parameters that controlled the distribution and nature of the trace fossils in the Bakken Formation. Sparse bioturbation, relatively low ichnodiversity, and the "impoverished" Cruziana ichnofacies characterize the marginalmarine deposits, suggesting stressful brackish-water conditions. Marine deposits from the middle member, in contrast, are highly bioturbated, with a moderate ichnodiversity and the "distal" Cruziana ichnofacies that flourished during fully marine well-oxygenated conditions. There is only a slight difference between the total ichnodiversity of the open-marine interval (ten ichnogenera) and that of the brackish-water interval (seven ichnogenera). Ichnodiversity should not be considered at face value and isolated from other aspects when evaluating stress levels in order to detect a brackish-water signal. Lack of bioturbation in the black shale of the lower and upper members resulted from anoxic conditions. The passage from anoxic (lower member) to well-oxygenated conditions (middle member) was gradational, as is revealed by the occurrence of oxygen-deficient trace-fossils at the top of the lower member. Finally, the contrasting styles in tempestite preservation in upper-offshore deposits from the lower and upper open-marine intervals is attributed to variations in the intensity and frequency of storm during deposition of the highstand and transgressive deposits.
The provenance of Jurassic and Lower Cretaceous clastic sediments offshore southwestern Nova Scotia
Canadian Journal of Earth Sciences, 2017
Jurassic and Cretaceous sandstones in the Shelburne subbasin and Fundy Basin, offshore Nova Scotia are poorly known, but are of current interest for petroleum exploration. The goal of this study is to determine the provenance of sandstones and shales, which will contribute to a better understanding of regional tectonics and paleogeography in the study area. Mineral and lithic clast chemistry was determined from samples from conventional cores and cuttings from exploration wells, using scanning electron microscope and electron microprobe. Whole-rock geochemical composition of shales was used to test the hypotheses regarding provenance of Mesozoic clastic sedimentary rocks in the SW Scotian Basin. Lower Jurassic clastic sedimentary rocks in the Fundy Basin contain magnetite, biotite and chlorite suggesting local supply from the North Mountain Basalt and Meguma Terrane, whereas pyrope and anthophyllite suggest small supply from distant sources. In the SW Scotian Basin, detrital minerals, lithic clasts and shale geochemistry from Middle Jurassic to Early Cretaceous indicate a predominant Meguma Terrane source, and transport by local rivers. Rare spinel and garnet grains of meta-ultramafic rocks, only in the Middle Jurassic at the Mohawk B-93 well, suggest minor supply from the rising Labrador rift, via the same river that transported distant sediments to the Fundy Basin. Lower Cretaceous sandstones from the Mohican I-100 well contain minor garnet, spinel and tourmaline from metaultramafic rocks, characteristic of sediment supplied to the central Scotian Basin at that time. The dominant Meguma Terrane provenance precludes thick deep-water sandstones in the eastern part of the Shelburne subbasin, but the evidence of Middle Jurassic distant river supply through the Fundy Basin is encouraging for deep water reservoir quality in the western part.
The Upper Devonian-Lower Mississippian Bakken Formation hosts one of the most important oil reservoirs in Saskatchewan. Integration of ichnological and sedimentological data indicates that deposition of Bakken strata occurred in two different paleoenvironmental settings: open-marine and brackish-water marginal marine. This paper focuses on the open-marine deposits in the Lower Member, the basal and the upper part of the Middle Member, and the Upper Member. The open-marine deposits embrace shelf, lower and upper offshore, offshore transition, and a transgressive lag facies. The large extension and continuity of the open-marine sedimentary facies point towards deposition in a low-gradient system in a shallow epeiric sea. With the exception of the black shale from the Lower and the Upper Member, all these deposits are characterized by a high bioturbation index and a "distal" Cruziana ichnofacies with Phycosiphon incertum and Nereites missouriensis as dominant elements, and Asterosoma isp., Planolites montanus, and Teichichnus rectus as subordinate elements.
CSPG Annual Convention – Program & Abstracts, 1999
The Upper Coniacian substage in the Western Canada Sedimentary Basin is characterized by relative sea level fall and basinward migration of littoral facies of the Cretaceous epicontinental seaway. During this interval (~86.2 to 85.5 Ma BP: 700 Kyrs.) the Marshybank Member of the Wapiabi Formation was deposited as a series of shoaling-upwards parasequences in shoreface to coastal plain sedimentary environments along the Alberta–Britsh Columbia provincial border. The top of this clastic wedge is marked by a sharply-defined regional disconformity, separating middle/upper shoreface or coastal plain siliciclastics and a laterally-persistent chert pebble and siderite nodule transgressive lag. Both are abruptly overlain by offshore marine mudstone (Dowling Mbr: Lower Santonian) in surface exposures throughout the Rocky Mountain Foothills (e.g. South Ram River). Near the southern limit of the Peace River Arch ("PRA"; township 69:W6), however, the typical Marshybank Mbr progradational sequence is capped by a ~1.0 m thick interval of thoroughly bioturbated fine to medium-grained sandstone containing 1.0–80% ooids composed principally of iron-rich phyllosilicate minerals (e.g. nontronite). These shallow-water deposits contain identical biostratigraphic index fossils and are very similar to iron ooid-bearing marine sandstones exposed along the Smoky River in township 76:W6, ~100 km farther north. In the PRA region these regressive facies are referred to as the Bad Heart Formation (Upper Coniacian: Scaphites depressus Zone), but are never represented at surface exposures in association with Marshybank Mbr facies. As Marshybank Mbr facies are not known from the PRA (defined by Leduc Fmn fringing reef trend; Bad Heart Fmn appears to be restricted within this area), this core interval allows for a rare glimpse of these two facies occurring together. (continued ...)
The architecture, distribution and facies of sandstone bodies in the Gog Group of the southern Rocky Mountains of Western Canada record the dynamics of sand movement on the broad continental shelf of West Laurentia during the Early Cambrian phase of worldwide transgression. These sandstones represent early deposits of a passive margin under high rates of sediment supply; accommodation was sustained by high rates of thermal subsidence plus sea-level rise. This study focuses on the stratigraphy and sedimentology in the Bow Valley region, specifically the sector from Mount Assiniboine northwest to the North Saskatchewan River. The objectives are to: 1) revise the existing stratigraphic nomenclature; 2) provide a general facies description and paleoenvironmental analysis of the constituent units; and 3) place the depositional setting in the context of the evolution of the Western Canada Sedimentary Basin.
2009
Relative to their occurrence in thick siliciclastic sections, thin carbonates show utility as sensitive indicators of the surrounding sand and shale sedimentation. When composed of in situ framebuilders (microbial and skeletal) as demonstrated by inter-growth position, bioerosion, associated submarine cements and marine geopetals, the carbonates are particularly helpful for environmental inferences. Within the Sable Island paleodelta, cores in Penobscot L-30 and West Venture C-62 show both dark colors and limited biotic diversity with microbial textures. The C-62 cores are particularly interesting because they provide an independent check on the shelf-margin delta model and sequence stratigraphic scenario presented by Cummings and Arnott for the Venture gas field. In less than 7 metres, facies and fauna in limestone change upward from a biotically depauperate marl to a microbial mud mound which is succeeded by an argillaceous sponge-microsolenid coral reef mound with some stromatoporoids and possible red algae. The sequence is interpreted to reflect a forced regression and falling sea level. This closely supports the published deltaic sequence stratigraphy as long as it is appreciated that the "condensed limestone facies" is actually a distal composite, recording changes in sea level, nutrient supply, and ultimately sediment type that replaces the carbonate as the delta progrades. The maximum flooding surface (MFS) occurs during the microbial mound stage, below an abrupt lithologic change across a pyritized hardground which is overlain by laminated black shale. This placement of the MFS reflects problematic differences in sequence stratigraphic concepts of carbonates versus siliciclastics. Relative to understanding the Abenaki platform, the C-62 core provides insights into relationships seen only in cuttings and sidewall cores in Queensland M-88 which drilled the slope and basin facies immediately in front of the Deep Panuke (Abenaki reservoir) gas field. M-88 and C-62 may be potential links for correlating and dating the massive (Abenaki) carbonates and the deltaic siliciclastics. (This is a much abbreviated version of Eliuk and Wach 2008 of 28 pages with 19 figures.