Nass River on the move: radar facies analysis of glaciofluvial sedimentation and its response to sea-level change in northwestern British Columbia

2006 ◽  
Vol 43 (11) ◽  
pp. 1733-1746 ◽  
Author(s):  
S J McCuaig ◽  
M C Roberts
Keyword(s):  
British Columbia ◽  
Sea Level ◽  
Facies Analysis ◽  
Late Glacial ◽  
Depositional Environments ◽  
Coarse Grained ◽  
Sea Levels ◽  
Stratal Architecture ◽  
Forced Regression ◽  
Radar Facies

The Nass Valley of northwestern British Columbia is a glacial fiord containing extensive glaciomarine and glaciofluvial sediments. Two parallel braidplains, separated by a bedrock ridge, were deposited within the fiord. Mapping of these deposits led to the hypothesis that the braidplains must have terminated at deltas. However, a lack of surface exposures meant that ground-penetrating radar was needed to investigate these deposits. Radar facies analysis aided in the identification of braidplain, braid delta and glaciomarine depositional environments, as well as underlying bedrock. Several deltas graded to different sea levels were discovered, allowing inferences to be made about the relationship of falling sea level to sediment architecture. The upper section of the western braidplain is graded to a sea level of 185 m above sea level (asl), indicating that the proto-Nass River flowed on the western side of the bedrock ridge when the sea was at that level. However, the river moved to the east side of the ridge as sea level fell, depositing the extensive Aiyansh Braidplain – Braid Delta, which is graded to a 152 m sea-level stand. Several other deltas also formed at this sea-level stand. Avulsion occurred and the river flowed on the west side of the ridge again when sea level fell to 134 m asl. The river remained in this position throughout late glacial time and eventually evolved into the modern Nass River. The coarse-grained deposits are indicative of forced regression, with both stepped-top attached and detached stratal architecture present.

Past Sea Levels, Eustasy and Deformation of the Earth

1972 ◽  
Vol 2 (1) ◽  
pp. 1-14 ◽  
Author(s):  
R. I. Walcott
Keyword(s):  
Sea Level ◽  
Late Glacial ◽  
The United States ◽  
Ground Subsidence ◽  
Postglacial Rebound ◽  
Vertical Movements ◽  
Sea Levels ◽  
Atlantic Seaboard ◽  
The Earth ◽  
Change In Mean

Vertical movements of the earth's surface related to postglacial rebound, the eustatic rise in sea level and the elastic deformation of the globe due to melting of late glacial ice sheets are calculated for simplified models of the earth. The movements of the ground are large and require a reevaluation of what is meant by eustatic sea level change. This is defined here as an ocean-wide average change in mean sea level and its measurement requires widely distributed observations weighted according to the areas of oceans they represent. Evidence of a postglacial (6000-0 years BP) relative rise in sea level comes largely from regions affected by ground subsidence related to adjacent upward postglacial rebound movements in deglaciated areas: evidence for a relative fall of sea level comes from coastlines well removed from areas of rebound and which have been affected by a rise of the continental areas through compensation for the eustatic load. It is concluded: (1) no substantial eustatic change of sea level in the past 6,000 years is required to explain postglacial sea levels: (2) in late glacial time the eustatic curve is probably more like the sea level curve of Texas and Mexico than that of the Atlantic seaboard of the United States: (3) that the information of past sea levels, when sufficiently widespread, can provide an important method of studying the deep mechanical structure of the earth.

A reconnaissance survey of late Quaternary sea levels, Bella Bella/Bella Coola region, central British Columbia coast

1978 ◽  
Vol 15 (3) ◽  
pp. 341-350 ◽  
Author(s):  
J. T. Andrews ◽  
R. M. Retherford
Keyword(s):  
British Columbia ◽  
Sea Level ◽  
Late Quaternary ◽  
Middle Part ◽  
Relative Sea Level ◽  
Marine Transgression ◽  
Sea Levels ◽  
Reconnaissance Survey ◽  
Rate Of Emergence ◽  
Bella Coola

A preliminary relative sea level curve that covers the last 10 200 years is derived for the area of the islands and outer mainland centered on Bella Bella and Namu, the central coast of British Columbia. The curve shows postglacial emergence of 17 m over this period. The rate of emergence was ~0.6 m/100 year about 9000 BP, and present sea level was attained between 7000 and 8000 BP. Relative sea level continued to fall until the last few hundred to one thousand years BP when a marine transgression led to a rise of sea level and resultant erosion of many coastal Indian middens. Marine limits on the outer islands may reach 120 m asl, whereas in the middle part of the fiord country observed delta surfaces are lower (54–75 m asl). Elevations of raised deltas then attain ~150 m at fiord heads. A readvance of the ice front ≤ 12 210 ± 330 BP (GSC-1351) is suggested by the stratigraphy of one section.

scholarly journals Granulometric and facies analysis of Middle–Upper Jurassic rocks of Ler Dome, Kachchh, western India: an attempt to reconstruct the depositional environment

Geologos ◽  
2019 ◽  
Vol 25 (1) ◽  
pp. 51-73 ◽  
Author(s):  
Asma A. Ghaznavi ◽  
M.A. Quasim ◽  
A.H.M. Ahmad ◽  
Sumit K. Ghosh
Keyword(s):  
Grain Size ◽  
Facies Analysis ◽  
Upper Jurassic ◽  
Depositional Environments ◽  
Coarse Grained ◽  
Energy Conditions ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Western India ◽  
Jurassic Rocks

Abstract Grain size analysis is an important sedimentological tool used to unravel hydrodynamic conditions, mode of transportation and deposition of detrital sediments. For the present study, detailed grain size analysis was carried out in order to decipher the palaeodepositional environment of Middle–Upper Jurassic rocks of the Ler Dome (Kachchh, western India), which is further reinforced by facies analysis. Microtextures were identified as grooves, straight steps and V-shaped pits, curved steps and solution pits suggesting the predominance of chemical solution activity. Grain size statistical parameters (Graphic and Moment parameters) were used to document depositional processes, sedimentation mechanisms and conditions of hydrodynamic energy, as well as to discriminate between various depositional environments. The grain size parameters show that most of the sandstones are medium- to coarse-grained, moderately to well sorted, strongly fine skewed to fine skewed and mesokurtic to platykurtic in nature. The abundance of medium- to coarse-grained sandstones indicates fluctuating energy levels of the deposition medium and sediment type of the source area. The bivariate plots show that the samples are mostly grouped, except for some samples that show a scattered trend, which is either due to a mixture of two modes in equal proportion in bimodal sediments or good sorting in unimodal sediments. The linear discriminant function analysis is predominantly indicative of turbidity current deposits under shallow-marine conditions. The C-M plots indicate that the sediments formed mainly by rolling to bottom suspension and rolling condition in a beach subenvironment. Log probability curves show that the mixing between the suspension and saltation populations is related to variable energy conditions.

Linking macrobenthic fauna and seismic facies to improve stratigraphic reconstructions: the case of the Mid Adriatic Depression since the late glacial period (Central Adriatic Sea)

2020 ◽  
Author(s):  
Michele Azzarone ◽  
Daniele Scarponi ◽  
Giulia Barbieri ◽  
Veronica Rossi ◽  
Claudio Pellegrini ◽  
...  
Keyword(s):  
Adriatic Sea ◽  
Benthic Fauna ◽  
Late Glacial ◽  
High Amplitude ◽  
Depositional Environments ◽  
Seismic Facies ◽  
Po River ◽  
Sedimentary Environments ◽  
Delta Plain ◽  
Stratal Architecture

<p>Direct observations from the geologic record are commonly used in conjunction with indirect seismo-stratigraphic inferences to detail environmental settings and stratal architecture of sedimentary successions. However, examples of integration between seismic facies and macrobenthic insights are scarce and limited to the use of such a group as auxiliary to other proxies. This case study investigated mollusc and ostracod dynamics along an onshore-offshore profile that intersects the C<sub>2</sub> clinothem (15.6 – 14.4 ky BP) of the Po River Lowstand Wedge (PRLW) and the overlying transgressive deposits formed in the central Adriatic Sea. Multivariate analyses were applied to benthic data to assess to what extent mollusc and ostracod assemblages can improve the resolution of seismic-derived depositional environments and stratigraphic architecture of cored succession. Along the profile of the C<sub>2</sub> clinothem, seismic reflection facies correspond with three sedimentary environments. Specifically, i) High Amplitude Continuous reflections (HAC) are interpreted as delta plain/subaqueous shelf; ii) High Amplitude Continuous Wavy Dipping reflections (HACWDip) characterize prodelta deposits, and iii) Low Amplitude Continuous reflections (LAC) are associated with distal basin settings. The integration of quantitative palaeoecologic trends with the seismic-derived depositional environments allowed the subdivision of the HAC facies into a proximal (core LSD-26) and a distal (cores LSD-27 and -28) area. In particular, the proximal area with HAC seismic facies encompasses semi-barred lower delta plain with vegetated substrates that evolves to more open, nearshore settings. Conversely, the distal area with HAC seismic facies is distinguished by clusters reminiscent of ecological mixing due to strong bioturbation and gravity flows in offshore transition/inner shelf settings. The paucity of benthic fauna for the units with HACWDip (core LSD-05) and LAC (core LSD-04) seismic facies, hampered a complete reconstruction of the palaeoenvironmental dynamics. However, both benthic groups investigated support the seismic-derived interpretation of shelf and basinal settings respectively, both subjected to high sedimentation rates. Moreover, the integration of mollusc and ostracod multivariate-derived trends with grain-size data across the study profile reveals distinctive stratal stacking patterns useful in constraining the position of key stratigraphic surfaces such as the Maximum Regressive Surface that marks the initial phase of the abandonment of the PRLW.</p>

Holocene sea-level change and delta growth: Fraser River delta, British Columbia

1989 ◽  
Vol 26 (9) ◽  
pp. 1657-1666 ◽  
Author(s):  
Harry F. L. Williams ◽  
Michael C. Roberts
Keyword(s):  
British Columbia ◽  
Sea Level Rise ◽  
Sea Level ◽  
Average Rate ◽  
Depositional Environments ◽  
Fraser River ◽  
Lithostratigraphic Units ◽  
Accretion Rates ◽  
Depositional Architecture ◽  
Holocene Sea Level

The Fraser River has been building its delta into the Strait of Georgia in southwestern British Columbia for about the last 9000 years. This period encompassed a relative sea-level rise of some 13 m. This study concerns the effects of the rise in sea level on the depositional evolution of the delta.The lithostratigraphy of the delta was established by a series of drill cores. Four major lithostratigraphic units were defined: peat, organic-rich silt, interbedded silts and sands, and massive sands. These units were interpreted in terms of the delta's contemporary depositional environments, including peat bog, floodplain, and intertidal zone.Analysis of the delta's depositional architecture and chronology indicates that the delta continued to prograde during the rise in sea level. A marine transgression, accompanied by the landward migration of marine and intertidal facies, did not occur. Growth of the delta during the rise in sea level was accomplished by both vertical accretion and lateral progradation.Vertical-accretion rates during the rise in sea-level averaged 2.4 mm/year and ranged up to about 5.3 mm/year. Lateral progradation of the delta was most rapid in the early stages of growth (9000 – 8000 years ago), when the average rate was 6.5 m/year, and slowest during the period of most rapid sea-level rise, when the rate declined to less than 1 m/year. The progradation rate of 2.4 m/year calculated for the most recent period (2250–present) compares well with estimates based on bathymetric surveys.A revised sea-level curve for the Fraser Lowland region is proposed on the basis of the identification of former sea-level positions in core at the lithologic transitions from tidal-marsh to intertidal deposits. The curve contains a hitherto unknown stillstand that occurred ca 6000 years ago and shows that the mid-Holocene sea-level rise continued until about 2250 years ago.

scholarly journals Stratigraphy and depositional evolution of the uppermost Oligocene –Miocene succession in western Denmark

2004 ◽  
Vol 51 ◽  
pp. 89-109 ◽  
Author(s):  
Erik Skovbjerg Rasmussen
Keyword(s):  
Sea Level ◽  
Middle Miocene ◽  
Depositional Environments ◽  
Sediment Supply ◽  
Coarse Grained ◽  
Sea Level Changes ◽  
Fluvial Systems ◽  
North East ◽  
The North ◽  
Tectonic Movements

The uppermost Oligocene – Miocene succession in Denmark is subdivided into six depositional sequences. The development of the succession was controlled both by tectonic movements and eustatic sea-level changes. Tectonic movements generated a topography, which influenced the depositional pattern especially during low sea level. This resulted in sediment by-pass on elevated areas and the confinement of fluvial systems to structural lows. Structural highs further created restricted depositional environments behind the highs during low sea level. The structural highs were also the locus for sandy spit deposits during transgression and high sea level. Initially sediment supply was from the north and north-east but shifted within the Middle Miocene to an easterly direction indicating a significant basin reorganisation at this time. Eustatic sea-level changes mainly controlledthe timing of sequence boundary development and the overall architecture of the sequences.Consequently, the most coarse-grained sediments were deposited within the forced regressive wedge systems tract, the lowstand systems tract and the early transgressive systems tract. The most distinct progradation occurred in the Aquitanian (Lower Miocene) and was associated with a cold period in central Europe.The subsequent rise of sea level until the Serravallian (Middle Miocene) resulted in an overall back-stepping stacking pattern of the sequences and in decreasing incision.

Holocene sea levels, paleoceanography, and late glacial ice configuration near the Northumberland Strait, Maritime Provinces

1987 ◽  
Vol 24 (4) ◽  
pp. 668-675 ◽  
Author(s):  
David B. Scott ◽  
Franco S. Medioli ◽  
Ann A. L. Miller
Keyword(s):  
Sea Level ◽  
Atlantic Coast ◽  
Late Glacial ◽  
Bay Of Fundy ◽  
Maritime Provinces ◽  
Glacial Ice ◽  
Sea Levels ◽  
Ice Caps ◽  
Present Rate ◽  
Nova Scotian

Work on new cores from old core sites in Baie Verte, New Brunswick, led to the identification of submerged salt-marsh peats, reported earlier as freshwater ones. A comprehensive sea-level curve, between 9 and 15 m below present, is based on marsh foraminiferal assemblages. These data indicate that between 4500 and 5400 BP relative sea-level (RSL) rise was comparatively slow (about 10 cm/100 years); the rate increased dramatically between 4500 and 4000 BP (1 m/100 years) and decreased between 2000 and 4000 BP to its present rate of 15 cm/100 years. We suggest RSL was falling before 5400 BP and that the sequence in our deepest core is similar to some observed in the Bay of Fundy and Nova Scotian Atlantic coast where early RSL fall is documented. To account for this sea-level record and others nearby we suggest that the ice history here is complex, with three separate ice caps thinning towards this area in late glacial times.Earlier work also indicated a number of sediment sequences barren of benthonic foraminifera, suggesting a complex marine–freshwater history for the area. The study of new cores containing the same sequences indicates no barren zones but a simple transgressive sequence with a warm-water calcareous fauna followed by an agglutinated transitional estuarine foraminiferal fauna.

Sea-level changes and depositional environments in the İzmit Gulf, eastern Marmara Sea, during the late glacial–Holocene period

2003 ◽  
Vol 202 (3-4) ◽  
pp. 159-173 ◽  
Author(s):  
M.N. Çağatay ◽  
N. Görür ◽  
A. Polonia ◽  
E. Demirbağ ◽  
M. Sakınç ◽  
...  
Keyword(s):  
Sea Level ◽  
Late Glacial ◽  
Depositional Environments ◽  
Marmara Sea ◽  
Sea Level Changes ◽  
Holocene Period

scholarly journals Facies Analysis and Depositional Stages of The Albian-Aptian Succession in Balad Oil Field, Central Iraq

2021 ◽  
Vol 54 (1B) ◽  
pp. 43-56
Author(s):  
Zainab Amer
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Facies Analysis ◽  
Depositional Environments ◽  
Oil Field ◽  
Delta Plain ◽  
Second Stage ◽  
The Third ◽  
Delta System ◽  
Distributary Channel

Carbonate-clastic succession which includes the Shu'aiba, Nahr Umr and Mauddud formations are representing a part of the Barremian-Aptian Sequence (Wasi'a Group). The present study includes three boreholes (Ba-1, 4 and 8) within the Balad Oil Field. The study area is located in central Iraq. This field represents a subsurface anticline with a northwest to southeast direction axis within the Mesopotamian Zone. Eight types of microfacies were recognized in the succession of the Mauddud and Shu’aiba formations. These microfacies represent shallow open marine, restricted and semi-restricted, reef - back reef, deep open marine and basinal depositional environments. While Nahr Umr Formation includes two successions, the first is the upper unit which is characterized by shale dominated rocks and the second is the lower unit which is characterized by sand-dominated rocks. Four major lithofacies were recognized in these two successions, they represent four depositional environments which are distributary channel, bay fill, delta plain and prodelta. The Albian-Aptian sequence was deposited during three cycles overlying the regional unconformity below the Shu’aiba Formation, the Zubair Formation, and ended with local unconformity with the Ahmadi Formation. The first stage is represented by deposition of Shu’aiba Formation during the sea-level rise after regression stage during the Zubair deposition which deposition in delta association facies. The second stage was showed a regressed of deposit the delta system above the shallow open marine of the Shu’aiba Formation, where the succession became characterized by mud-dominated rock with fissile and organic material. The third depositional stage is represented by the continuation of sea-level rise. This transgression leads to the building of carbonate ramp of the Mauddud Formation above the deltaic system of Nahr Umr Formation with a conformable surface. The Mauddud depositional stage was represented by two cycles of transgression succession, where appeared deepening upward in both cycles. The unconformity between these formations have been determined by observing the glauconite mineral and detected by log response in depth 2880m in well Ba-1.

scholarly journals A forced regressive shelf-margin wedge formed by transition-slope progradation: lowermost Cretaceous Rauk Plateau Member, Jameson Land, East Greenland

2005 ◽  
Vol 52 ◽  
pp. 227-243 ◽  
Author(s):  
F. Surlyk
Keyword(s):  
Sea Level ◽  
Large Scale ◽  
Coarse Grained ◽  
Shelf Edge ◽  
High Angle ◽  
Seismic Profiles ◽  
East Greenland ◽  
Shelf Slope ◽  
Forced Regression ◽  
Shelf Margin

The Middle Jurassic – lowermost Cretaceous succession of Jameson Land, East Greenland records a marine, overall regressive–transgressive–regressive cycle with regressive maxima in the Late Bajocian and Late Volgian separated by a transgressive maximum in the Kimmeridgian. Smaller-scale regressive interludes took place in the Late Callovian and Mid Oxfordian. A shelf-slope-basin physiography started to develop in the Late Callovian due to increasing rifting and a relief of several hundred metres was attained during maximum end-Jurassic regression and deposition of the Volgian Raukelv Formation. The formation consists of a forestepping stack of laterally extensive shelf-edge wedges, each several tens of metres thick, composed of coarse-grained sandstone, showing highangle clinoform bedding and containing marine body and trace fossils. These clinoform beds are superimposed on the large-scale clinoforms of the shelf–slope–basin. The wedges onlap older shelf deposits in a landward direction and are overlain by thin transgressive sandstones or mudstones, or directly by the next coarse-grained wedge. The top wedge, comprising the Rauk Plateau Member, is of Late Volgian (i.e. earliest Cretaceous) age and is characterized by steep clinoforms truncated by internal erosional downlap surfaces. The clinoforms are simple avalanche beds, a few tens of centimetres thick, or they may be several metres thick and contain large-scale cross-bedded intrasets of probable tidal origin. The erosional events were associated with downshift of the succeeding clinoforms, recording minor sea-level fall and forced regression. The top surface of the Rauk Plateau wedge is incised by a system of minor channels leading to a large canyon-like valley. The wedge was deposited by transition-slope progradation below wave base during a period of sea-level stillstand punctuated by minor, stepwise falls. It provides an excellently exposed example of a laterally derived, coarse-grained shelf-margin wedge, showing high-angle clinoform bedding and representing an ancient counterpart to Holocene and Late Pleistocene prograding infralittoral wedges seen on seismic profiles across Mediterranean shelf edges.

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