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.

Subsidence and sea-level rise in the Thames Estuary

1972 ◽  
Vol 272 (1221) ◽  
pp. 121-130 ◽  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Average Rate ◽  
Thames Estuary ◽  
The North ◽  
Storm Waves ◽  
Late Cretaceous Period ◽  
The North Sea ◽  
Sea Area ◽  
Cretaceous Period

The development of the area, of the Thames Estuary is briefly traced since the late Cretaceous period, with its present outline being due to a combination of factors. The overall subsidence of the North Sea area, the ‘Alpine5 fold movements, and the transgression of the sea since the retreat of the Weichselian icesheets have all contributed. The positions of the shore-line during the critical phase, 9600 b.p. to 8000 b.p., of this last transgression of the sea are shown. Subsequent to this main transgressive phase, erosion of the shoreline has been rapid due to storm-waves and tidal current action. An estimation of the average rate of subsidence and/or sea-level rise is given based on the concept of sedimentary equilibrium in which a figure of 12.7 cm (5 in) per century is arrived at.

scholarly journals Late Holocene sea-level change around Newfoundland

2007 ◽  
Vol 44 (10) ◽  
pp. 1453-1465 ◽  
Author(s):  
Julia F Daly ◽  
Daniel F Belknap ◽  
Joseph T Kelley ◽  
Trevor Bell
Keyword(s):  
Salt Marsh ◽  
Sea Level Rise ◽  
Sea Level ◽  
Late Holocene ◽  
Sea Level Change ◽  
Laurentide Ice Sheet ◽  
Change Analysis ◽  
Level Change ◽  
Rising Sea Level ◽  
Holocene Sea Level

Differential sea-level change in formerly glaciated areas is predicted owing to variability in extent and timing of glacial coverage. Newfoundland is situated close to the margin of the former Laurentide ice sheet, and the orientation of the shoreline affords the opportunity to investigate variable rates and magnitudes of sea-level change. Analysis of salt-marsh records at four sites around the island yields late Holocene sea-level trends. These trends indicate differential sea-level change in recent millennia. A north–south geographic trend reflects submergence in the south, very slow sea-level rise in the northeast, and a recent transition from falling to rising sea-level at the base of the Northern Peninsula. This variability is best explained as a continued isostatic response to deglaciation.

The physical sustainability of the coastal zone of the Ganges-Brahmaputra-Meghna delta under climatic and anthropogenic stresses

2021 ◽  
Author(s):  
Stephen Darby ◽  
Md. Munsur Rahman ◽  
Anisul Haque ◽  
Robert Nicholls ◽  
Frances Dunn
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Average Rate ◽  
River Management ◽  
Tidal River ◽  
Natural Conditions ◽  
Fluvial Sediment ◽  
Average Value ◽  
Delta Plain ◽  
The Ganges

<p>The Ganges-Brahmaputra-Meghna (GBM) delta is one of the world’s largest deltas, and consists of large areas of low flat lands formed by the deposition of sediment from the GBM rivers. However, recent estimates have projected between 200~1000 mm of climate-driven sea-level rise by the end of the 21st century, at an average rate of ~6 mm/yr. Eustatic sea-level rise is further compounded by  subsidence of the delta, which in the coastal fringes varies from 0.2 to 7.5 mm/yr, at an average value of ~2.0 mm/yr. Therefore, the combined effect of sea-level rise and subsidence (termed relative sea-level rise, RSLR) is around 8.0 mm/yr. Such high values of RSLR raise the question of whether sediment deposition on the surface of the delta is sufficient to maintain the delta surface above sea level. Moreover, as the total fluvial sediment influx to the GBM delta system is known to be decreasing, the retained portion of fluvial sediment on the delta surface is also likely decreasing, reducing the potential to offset RSLR. Within this context, the potential of various interventions geared at promoting greater retention of sediment on the delta surface is explored using numerical experiments under different flow-sediment regime and anthropogenic interventions.  We find that for the existing, highly managed, conditions, the retained portion of fluvial sediment on the delta surface varies between 22% and 50% during average (when about 20% of the total floodplain in the country is inundated) and extreme (> 60% of the total floodplain in the country is inundated) flood years, respectively. However, the degree to which sediment has the potential to be deposited on the delta surface increases by up to 10% when existing anthropogenic interventions such as polders that act as barriers to delta-plain sedimentation are removed. While dismantling existing interventions is not a politically realistic proposition, more quasi-natural conditions can be reestablished through local- sediment management using tidal river management, cross dams, dredging, bandal-like structures and/or combinations of the above measures.</p>

Holocene sea-level history of the Canadian Beaufort shelf

1993 ◽  
Vol 30 (1) ◽  
pp. 103-108 ◽  
Author(s):  
Philip R. Hill ◽  
Arnaud Héquette ◽  
Marie-Hélène Ruz
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Zone ◽  
Marine Sediments ◽  
Tidal Marsh ◽  
Relative Sea Level ◽  
The Holocene ◽  
Single Piece ◽  
History Of ◽  
Holocene Sea Level

New radiocarbon ages pertaining to the Holocene sea-level history of the Canadian Beaufort shelf are presented. The ages were obtained on samples of freshwater and tidal-marsh peat beds from offshore boreholes and shallow cores in the coastal zone and on molluscs and a single piece of wood deposited in foraminifera-bearing marine sediments. Although none of the samples record directly the position of relative sea level, the suite of ages constrains the regional curve sufficiently to suggest a faster rate of mid Holocene sea level rise (7–14 mm/a) than previously thought. The rate of relative rise slowed markedly in the last 3000 years, approaching the present at a maximum probable rate of 2.5 mm/a.

Ice sheet mass balance and sea level

2009 ◽  
Vol 21 (5) ◽  
pp. 413-426 ◽  
Author(s):  
I. Allison ◽  
R.B. Alley ◽  
H.A. Fricker ◽  
R.H. Thomas ◽  
R.C. Warner
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Average Rate ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Measurement Technology ◽  
Satellite Gravity ◽  
Intergovernmental Panel ◽  
Ice Sheet Mass Balance

AbstractDetermining the mass balance of the Greenland and Antarctic ice sheets (GIS and AIS) has long been a major challenge for polar science. But until recent advances in measurement technology, the uncertainty in ice sheet mass balance estimates was greater than any net contribution to sea level change. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (AR4) was able, for the first time, to conclude that, taken together, the GIS and AIS have probably been contributing to sea level rise over the period 1993–2003 at an average rate estimated at 0.4 mm yr-1. Since the cut-off date for work included in AR4, a number of further studies of the mass balance of GIS and AIS have been made using satellite altimetry, satellite gravity measurements and estimates of mass influx and discharge using a variety of techniques. Overall, these studies reinforce the conclusion that the ice sheets are contributing to present sea level rise, and suggest that the rate of loss from GIS has recently increased. The largest unknown in the projections of sea level rise over the next century is the potential for rapid dynamic collapse of ice sheets.

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