The basal unconformity of the Nanaimo Group, southwestern British Columbia: a Late Cretaceous storm-swept rocky shoreline

2006 ◽  
Vol 43 (8) ◽  
pp. 1165-1181 ◽  
Author(s):  
P D Johnstone ◽  
P S Mustard ◽  
J A MacEachern
Keyword(s):  
British Columbia ◽  
Sediment Supply ◽  
Storm Activity ◽  
Fine Grained ◽  
Accommodation Space ◽  
Facies Associations ◽  
Intrusive Rocks ◽  
Coastal Cliffs ◽  
Sandstone Facies ◽  
High Sediment

The Turonian to Santonian Comox Formation forms the basal unit of the Nanaimo Group. In the southern Gulf Islands of British Columbia, the Comox Formation nonconformably overlies Devonian metavolcanic and Jurassic intrusive rocks and is interpreted to reflect a rocky foreshore reworked by waves and ultimately drowned during transgression. The nonconformity displays a relief of metres to tens of metres. Basal deposits vary in thickness, as does the facies character along the several kilometres of paleoshoreline studied. In the study area, three distinct but related environments are expressed, typical of a complex rocky shoreline with headlands and protected coves. Crudely stratified conglomerates represent gravel-dominated fans characterized by debris-flow processes, building out from local coastal cliffs and gullies directly onto the rocky shoreline. Fine-grained basal units represent shoreline environments protected from higher energy shoreline processes, presumably in small embayments. Sandstone facies associations reflect storm-dominated shoreface environments. The unusual thickness and coarseness of these shoreface intervals suggest a combination of increasing accommodation space, proximal and high sediment supply, and high frequency and energy of storm activity. This, in turn, suggests that the majority of the shoreline was exposed to the full effects of large, open-ocean storms. This interpretation differs from most previous models for the lower Nanaimo Group, which suggest that deposition occurred in more sheltered strait or bay environments.

scholarly journals TECTONOSEDIMENTARY SIGNIFICANCE OF THE MESSINIA CONGLOMERATES (SW PELOPONNESE, GREECE)

2017 ◽  
Vol 43 (2) ◽  
pp. 715
Author(s):  
A. Pavlopoulos ◽  
E. Kamperis ◽  
S. Sotiropoulos ◽  
M. Triantaphyllou
Keyword(s):  
Flow Direction ◽  
Foreland Basin ◽  
Sediment Supply ◽  
Accommodation Space ◽  
Gravity Flows ◽  
Facies Associations ◽  
Rapid Changes ◽  
Gravity Driven ◽  
Main Flow Direction ◽  
Lateral Variations

The marine fill of the Gavrovo-Tripolis foreland basin in the Messinia area (SW Peloponnese), includes facies and facies associations, deposited by sediment gravity flows in slope and inner fan settings. The above-mentioned gravity-driven sedimentary processes, resulted in the formation of thinning-upward sequences and fining fan facies associations, composed of impressive sheet-conglomerates at the base (Agia Mavra, Agia Varvara and Mali units), presenting mainly normal internal structure, while clay and sand-clay members predominate at the top. These conglomerates advocate a significant sediment supply and extended accommodation space, during periods of dramatic tectonic uplift, associated with the westward propagation of Pindos thrust front. In the prograding fan system, dominate paleo-currents with main flow direction to southwest. The finer fan facies associations show rapid lateral variations, both in lithology and thickness, indicating rapid changes in the inner, incised, part of the foredeep. Nannofossil analyses suggest that the sedimentation took place during Oligocene (NP22 to NP24 biozones). Three NNW-SSE trending thrust fault zones bound the above-mentioned units and they caused an important structural thickening of the fan facies associations. Biostratigraphic analyses date the end of the thrust activity in GavrovoTripolis zone in Late Oligocene (biozone NP24).

Stratigraphy and palaeoenvironmental interpretation of late Quaternary colluvial slope deposits in southern Africa

2021 ◽  
Author(s):  
J. Knight
Keyword(s):  
Southern Africa ◽  
Land Surface ◽  
Late Quaternary ◽  
Ecological Factors ◽  
Surface Instability ◽  
Sediment Supply ◽  
Spatial And Temporal Patterns ◽  
Catchment Scale ◽  
Accommodation Space ◽  
Slope Sediment

Abstract Slope and lowland sediment systems throughout southern Africa are dominated by the presence of colluvium with interbedded palaeosols and hardground duricrusts. These sediments correspond to phases of land surface instability and stability, respectively, during the late Quaternary. This study examines the stratigraphy and environmental interpretation of slope sediment records from specific sites in southern Africa for the period of marine isotope stages (MIS) 6 to 1 (~191 ka to present), informed by theoretical ideas of the dynamics of slope systems including sediment supply and accommodation space. Based on this analysis, phases of land surface instability and stability for the period MIS 6 to 1 are identified. The spatial and temporal patterns of land surface conditions are not a simple reflection of climate forcing, but rather reflect the workings of slope systems in response to climate in addition to the role of geologic, edaphic and ecological factors that operate within catchment-scale sediment systems. Considering these systems dynamics can yield a better understanding of the usefulness and limitations of slope sediment stratigraphies.

Telluride Mineralogy of the Deer Horn Au-Ag-Te-(Bi-Pb-W) Deposit, British Columbia: Implications for the Generation of Tellurides

2021 ◽  
Author(s):  
Jordan A. Roberts ◽  
Lee A. Groat ◽  
Paul G. Spry ◽  
Jan Cempírek
Keyword(s):  
British Columbia ◽  
Fluid Inclusions ◽  
Hanging Wall ◽  
Oscillatory Zoning ◽  
Stage Iii ◽  
Fine Grained ◽  
Melting Temperatures ◽  
Homogenization Temperatures ◽  
Intrusive Suite ◽  
Cathodoluminescence Imaging

ABSTRACT The Deer Horn deposit, located 150 km south of Smithers in west-central British Columbia, is an Eocene polymetallic system enriched in Au-Ag-Te with lesser amounts of Bi-Pb-W; the Au and Ag are hosted in Te-bearing minerals and Ag-rich gold (Au-Ag alloy). A quartz-sulfide vein system containing the main zones of Au-Ag-Te mineralization and attendant sericite alteration occurs in the hanging wall of a local, spatially related thrust fault and is genetically related to the nearby Eocene Nanika granodiorite intrusive suite. Tellurium-bearing minerals commonly form isolated euhedral to subhedral grains or composite grains (up to 525 μm in size) of Ag-, Bi-, Pb-, and Au-rich tellurium-bearing minerals (e.g., hessite, tellurobismuthite, volynskite, altaite, and petzite). Panchromatic cathodoluminescence imaging revealed four generations of quartz. Within remnant cores of quartz I, local oscillatory zoning occurs in quartz II. Fine-grained veinlets of quartz III and IV crosscut quartz I and II, showing evidence of at least two deformation events; late-forming veinlets of calcite crosscut all generations of quartz. The tellurides and Ag-rich gold occur in stage III quartz. Three types of fluid inclusions were observed in stage III and IV quartz: (1) aqueous liquid and vapor inclusions (L-V); (2) aqueous carbonic inclusions (L-L-V); and (3) carbonic inclusions (vapor-rich). Primary fluid inclusions related to the telluride mineralization within quartz III were tested with microthermometry, along with a few primary inclusions from quartz IV. Homogenization temperatures are 130.0–240.5 °C for L-V inclusions and 268.0–336.4 °C for L-L-V inclusions. Aqueous carbonic inclusions had solid CO2 melting temperatures from –62.1 to –56.8 °C, indicating the presence of ≈1 to 30 mol.% dissolved methane in these inclusions. The Deer Horn Au-Ag-Te-(Bi-Pb-W) deposit is a reduced intrusion-related gold system characterized by sheeted veins, metal zoning, low salinity aqueous-carbonic fluids, and a genetic relationship to an Eocene granodiorite. Values of δ34S of pyrite vary from –1.6 to 1.6 per mil and are compatible with a magmatic source of sulfur.

scholarly journals High resolution stratigraphy of initial stages of rifting, Sergipe-Alagoas Basin, Brazil

2017 ◽  
Vol 47 (4) ◽  
pp. 657-671 ◽  
Author(s):  
Carrel Kifumbi ◽  
Claiton Marlon dos Santos Scherer ◽  
Fábio Herbert Jones ◽  
Juliano Kuchle
Keyword(s):  
Radical Change ◽  
High Rate ◽  
Tectonic Activity ◽  
Accommodation Space ◽  
Facies Associations ◽  
Half Graben ◽  
Lateral Connection ◽  
Depositional Units ◽  
Two Parameters ◽  
Channel Deposits

ABSTRACT: The present work aims to characterize the Neo-Jurassic to Neocomian succession of the Sergipe-Alagoas Basin, located in northeast region of Brazil, in order to discover the influence of tectonics on sedimentation in detailed scale and thus separating this sedimentary succession in tectono-stratigraphic units. Fieldwork observations and stratigraphic sections analysis allowed subdividing this rift succession into three depositional units that indicate different paleogeographic contexts. Unit I, equivalent to the top of Serraria Formation, is characterized by braided fluvial channel deposits, with paleocurrent direction to SE; unit II, corresponding to the base of Feliz Deserto Formation, is composed of anastomosed fluvial channel and floodplain facies associations; and unit III, equivalent to the major part of Feliz Deserto Formation, is characterized by delta deposits with polymodal paleocurrent pattern. The changes of depositional system, as well as paleocurrent direction, suggest that the previously described units were deposited in different evolutionary stages of rifting. Units I and II represent the record of a wide and shallow basin associated with the first stage of rifting. Unit I is characterized by incipient extensional stress generating a wide synclinal depression, associated to the low rate of accommodation and low tectonic activity. These two parameters progressively increase in unit II. The paleocurrent direction of unit I indicates that the depocenter of this wide basin was located at SE of the studied area. No conclusion could be done on paleocurrent from unit II because of the low amount of measurements. Unit III suggests a second stage marked by a deeper basin context, with a high rate of accommodation space associated with the lateral connection of faults and individualization of the half-graben. The scattering in the paleocurrent direction in this unit indicates sedimentary influx coming from several sectors of the half-graben. The boundary between these two stages is marked by a flooding surface that indicates an extremely fast transition and suggests a radical change in geometric characteristics of the basin due to the increase of tectonic activity.

scholarly journals Characterization of volcanic and intrusive rocks across the British Columbia - Yukon border, GEM 2 Cordillera

2014 ◽  
Author(s):  
A Zagorevski ◽  
M G Mihalynuk ◽  
N Joyce ◽  
K Martin
Keyword(s):  
British Columbia ◽  
Intrusive Rocks

scholarly journals Lithostratigraphy and late Cenozoic fluvial styles of Siwalik Group along Kankai River section, East Nepal Himalaya

1970 ◽  
Vol 12 ◽  
pp. 63-74 ◽  
Author(s):  
Prakash Das Ulak
Keyword(s):  
Grain Size ◽  
River Section ◽  
Late Cenozoic ◽  
Nepal Himalaya ◽  
Fine Grained ◽  
The North ◽  
Lithostratigraphic Units ◽  
Facies Associations ◽  
Siwalik Group ◽  
Southern Flank

This paper describes on lithostratigraphy as well as evolution of the fluvial styles in late Cenozoic Siwalik Group along the Kankai River section of east Nepal Himalaya. The Siwalik Group lies on the southern flank of the Himalaya, is composed of molasse sediments, which were derived from the rising Himalaya in the north. The group along the Kankai River section is lithologically divided into the Lower, Middle and Upper Siwaliks, in ascending order based on increasing grain size and lithology. The Lower Siwaliks is subdivided into the lower and upper members, whereas the Middle Siwaliks is subdivided into the lower, middle and upper members on the basis of the relative thickness of the sandstone and mudstone beds, frequency of occurrence of these beds, and grain size of sandstone. The Upper Siwaliks is subdivided into the lower and upper members based on the clast size in conglomerate and constituent of the Siwalik sandstone boulders in conglomerate. Based on the lithology, assemblages of sedimentary structure and sediment body architectures, seven facies associations (FA1 to FA7) are recognised. These facies associations are closely related to each lithostratigraphic units of the area. The sediments of the lower and upper members of the Lower Siwaliks are products of the fine-grained meandering and flood flow-dominated meandering systems, respectively. The lower, middle and upper members of the Middle Siwaliks are interpreted as the deposits by sandy meandering, deep sandy braided and shallow braided systems, respectively whereas the lower and upper members of the Upper Siwaliks are the products of gravelly braided to debris flow-dominated braided systems, respectively.   doi: 10.3126/bdg.v12i0.2251 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 63-74

scholarly journals Bedrock incision by bedload: insights from direct numerical simulations

2016 ◽  
Author(s):  
Guilhem Aubert ◽  
Vincent J. Langlois ◽  
Pascal Allemand
Keyword(s):  
Numerical Approach ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Analytical Models ◽  
Water Stream ◽  
Direct Measurements ◽  
Bedload Sediment ◽  
Discrete Element Simulations ◽  
High Sediment

Abstract. Bedload sediment transport is one of the main processes that contribute to bedrock incision in a river and is therefore one of the key control parameters in the evolution of mountainous lanscapes. In recent years, many studies have addressed this issue through experimental setups, direct measurements in the field or various analytical models. In this article, we present a new direct numerical approach: using the classical methods of discrete element simulations applied to granular materials, we compute explicitely the trajectories of a number of pebbles entrained by a turbulent water stream over a rough solid surface. This method allows us to extract quantitatively the amount of energy that successive impacts of pebbles deliver to the bedrock, as a function of both the amount of sediment available and the Shields number. We show that we reproduce qualitatively the behaviour observed experimentally by Sklar and Dietrich (2001) and observe both a "tool-effect" and a "cover- effect". Converting the energy delivered to the bedrock into an average long-term incision rate of the river leads to predictions consistent with observations in the field. Finally, we reformulate the dependency of this incision rate with Shields number and sediment flux, and predict that the cover term should decay linearly at low sediment supply and exponentially at high sediment supply.

scholarly journals Growth faults affecting depositional geometry, facies and sequence stratigraphy record on a carbonate platform edge (South Vercors Urgonian platform, SE France)

2019 ◽  
Vol 190 ◽  
pp. 1
Author(s):  
Serge Ferry ◽  
Danièle Grosheny
Keyword(s):  
Small Area ◽  
Carbonate Platform ◽  
Growth Fault ◽  
Sequence Stratigraphic ◽  
Fine Grained ◽  
Accommodation Space ◽  
Western Side ◽  
The Waves ◽  
Se France ◽  
Depositional Geometries

The first two calcarenite units at the base of the Urgonian limestones on the southern edge of the platform bear different depositional geometries depending on place (Cirque d’Archiane to Montagnette and Rocher de Combau). The lower calcarenite unit (Bi5 of Arnaud H. 1981. De la plate-forme urgonienne au bassin vocontien. Le Barrémo-Bédoulien des Alpes occidentales entre Isère et Buëch (Vercors méridional, Diois oriental et Dévoluy). Géologie Alpine, Grenoble, Mémoire 12: 3. Disponible sur https://tel.archives-ouvertes.fr/tel-00662966/document), is up to 200 m thick and shows three different patterns, in terms of accommodation space, from the western Archiane Cirque to the Montagnette to the east. On the western side of the Cirque, the unit begins on slope fine-grained limestone with thin sigmoïdal offlap geometry, suggesting little available space after a relative sea level fall. It is overlain by thick progradational/aggradational, then purely aggradational calcarenite capped by a coral and rudist-bearing bed. This bed is, therefore, interpreted as a maximum (although moderate) flooding facies. The depositional geometry is different on the eastern side of the Cirque, where a progradational pattern in the lower part of the unit is interrupted by a rotational movement affecting the depositional profile. The deformation promoted aggradation updip and retrogradation downdip as a result of starvation. The inferred growth fault updip (thought to be responsible for the change) began to function earlier at the Montagnette, explaining the huge calcarenite clinoforms found there, filling a deeper saddle created in the depositional profile. The same fault probably was reactivated later during the deposition of the overlying, thinner Bi6-1 unit, which appears at Rocher de Combau with an uncommon tidal facies at the base. A rotational bulge, created by the inferred growth fault, would have protected a small area behind it to spare the local calcarenite deposition from the waves for a while. These two examples show that sequence stratigraphic interpretation may differ from one place to the other, and even show opposite trends due to this kind of disturbance.

APPROACHES TO PALAEOGEOGRAPHIC RECONSTRUCTIONS OF THE LATROBE GROUP, GIPPSLAND BASIN, SOUTHEASTERN AUSTRALIA

2005 ◽  
Vol 45 (1) ◽  
pp. 581 ◽  
Author(s):  
T. Bernecker ◽  
A.D. Partridge
Keyword(s):  
Co2 Storage ◽  
Depositional Environments ◽  
Petroleum Systems ◽  
Fine Grained ◽  
Southeastern Australia ◽  
Depositional System ◽  
Facies Associations ◽  
Marine Fossils ◽  
Coal Accumulation ◽  
Gippsland Basin

In the Gippsland Basin, the seaward extent of paralic coal occurrences can be mapped in successive time slices through the Paleocene and Eocene to provide a series of straight to gently arcuate surrogate palaeoshorelines within the petroliferous Latrobe Group. Palaeogeographic reconstructions that incorporate this information provide a unique perspective on the changes affecting a siliciclastic depositional system on a passive continental margin where basin development has been primarily controlled by thermal sag. In contrast, the absence of calcareous marine fossils and lack of extensive, widespread and thick fine-grained sediments on the marine shelf and continental slope, beyond the seaward limits of coal accumulation, have contributed to the false impression that the Latrobe Group accumulated in a largely non-marine basin. Based on the proposed model for palaeoshoreline delineation, seismic data, sequence analysis, petrography and palynology can be integrated to subdivide the main depositional environments into distinct facies associations that can be used to predict the distribution of petroleum systems elements in the basin. The application of such palaeogeographic models to the older section of the Latrobe Group can improve the identification of these petroleum systems elements in as yet unexplored parts of the Gippsland Basin. Given the recent attention paid to the basin as a CO2 storage province, palaeogeographic interpretations may be able to assist with the selection of appropriate injection sites.

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