Sedimentary record of Harrison Lake: implications for deglaciation in southwestern British Columbia

1991 ◽  
Vol 28 (5) ◽  
pp. 800-815 ◽  
Author(s):  
Joseph R. Desloges ◽  
Robert Gilbert
Keyword(s):  
Surface Sediments ◽  
Hot Springs ◽  
Late Glacial ◽  
High Energy ◽  
The South ◽  
Sedimentary Record ◽  
Sea Levels ◽  
Transparent Layer ◽  
The North ◽  
Lake Cores

A sedimentary record from 60 km long Harrison Lake was constructed by using 3.5 kHz subbottom acoustic profiles and gravity cores of surface sediments. In places, the glaciolacustrine sediments exceed 70 m in thickness and represent the entire deglacial and postglacial accumulation record. An upper, acoustically transparent layer decreases in thickness from 12 to 4 m. southward from the upper lake. Cores from the upper metre of this layer demonstrate that deposition is dominated by settling of suspended sediment transported in a laterally mixed, wind-driven surface plume from the north. Depositional rates, inferred from 14C dating of organic macrofossils and counting of probable annual laminated couplets in the cores, are almost 2 mm/a in the north and decline to less than 0.1 mm/a in the south. Hence, the upper acoustic layer accounts for all postglacial (last 10 500 years BP) lacustrine deposition, with most of the sediment derived from Lillooet River. A lower, thicker (12–22 m), acoustically stratified layer is interpreted as high-energy glaciolacustrine deposits. This large volume of deglaciation sediment is derived from two sources: (i) ice retreating rapidly northwest up the Lillooet valley, which may have existed for no more than 400 years in the lower valley prior to opening of Lillooet Lake (which now traps most sediment derived from the upper basin); and (ii) inflow from the south as the late-glacial Fraser River rapidly built a delta north from the sill at Harrison Hot Springs. Despite known higher sea levels during deglaciation of the eastern Fraser Lowland, we have no evidence for a marine incursion.

scholarly journals Numerical modelling of the Caspian Sea tides

Ocean Science ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 209-219
Author(s):  
Igor P. Medvedev ◽  
Evgueni A. Kulikov ◽  
Isaac V. Fine
Keyword(s):  
Caspian Sea ◽  
Ocean Model ◽  
Tidal Range ◽  
The South ◽  
Tidal Dynamics ◽  
The Caspian Sea ◽  
Sea Levels ◽  
The North ◽  
Anticlockwise Rotation ◽  
Diurnal Tides

Abstract. The Caspian Sea is the largest enclosed basin on Earth and a unique subject for the analysis of tidal dynamics. Tides in the basin are produced directly by the tide-generating forces. Using the Princeton Ocean Model (POM), we examine details of the spatial and temporal features of the tidal dynamics in the Caspian Sea. We present tidal charts of the amplitudes and phase lags of the major tidal constituents, together with maps of the form factor, tidal range, and tidal current speed. Semi-diurnal tides in the Caspian Sea are determined by a Taylor amphidromic system with anticlockwise rotation. The largest M2 amplitude is 6 cm and is located in Türkmen Aylagy (called Turkmen Bay hereafter). For the diurnal constituents, the Absheron Peninsula separates two individual amphidromes with anticlockwise rotation in the north and in the south. The maximum K1 amplitudes (up to 0.7–0.8 cm) are located in (1) the south-eastern part of the basin, (2) Türkmenbaşy Gulf, (3) Mangyshlak Bay; and (4) Kizlyar Bay. As a result, the semi-diurnal tides prevail over diurnal tides in the Caspian Sea. The maximum tidal range, of up to 21 cm, has been found in Turkmen Bay. The strongest tidal currents have been located in the straits to the north and south of Ogurja Ada, where speeds reach 22 and 19 cm s−1, respectively. Numerical simulations of the tides using different mean sea levels (within a range of 5 m) indicate that spatial features of the Caspian Sea tides are strongly sensitive to changes in mean sea level.

scholarly journals Sedimentology and sequence stratigraphy of paralic and shallow marine Upper Jurassic sandstones in the northern Danish Central Graben

2003 ◽  
Vol 1 ◽  
pp. 367-402 ◽  
Author(s):  
Peter N. Johannessen
Keyword(s):  
Sea Level ◽  
Upper Jurassic ◽  
High Energy ◽  
Salt Dome ◽  
The South ◽  
The West ◽  
Relative Sea Level ◽  
Shallow Marine ◽  
The North ◽  
Plateau Area

Paralic and shallow marine sandstones were deposited in the Danish Central Graben during Late Jurassic rifting when half-grabens were developed and the overall eustatic sea level rose. During the Kimmeridgian, an extensive plateau area consisting of the Heno Plateau and the Gertrud Plateau was situated between two highs, the Mandal High to the north, and the combined Inge and Mads Highs to the west. These highs were land areas situated on either side of the plateaus and supplied sand to the Gertrud and Heno Plateaus. Two graben areas, the Feda and Tail End Grabens, flanked the plateau area to the west and east, respectively. The regressive–transgressive succession consists of intensely bioturbated shoreface sandstones, 25–75 m thick. Two widespread unconformities (SB1, SB2) are recognised on the plateaus, forming the base of sequence 1 and sequence 2, respectively. These unconformities were created by a fall in relative sea level during which rivers may have eroded older shoreface sands and transported sediment across the Heno and Gertrud Plateaus, resulting in the accumulation of shoreface sandstones farther out in the Feda and Tail End Grabens, on the south-east Heno Plateau and in the Salt Dome Province. During subsequent transgression, fluvial sediments were reworked by high-energy shoreface processes on the Heno and Gertrud Plateaus, leaving only a lag of granules and pebbles on the marine transgressive surfaces of erosion (MTSE1, MTSE2). The sequence boundary SB1 can be traced to the south-east Heno Plateau and the Salt Dome Province, where it is marked by sharp-based shoreface sandstones. During low sea level, erosion occurred in the southern part of the Feda Graben, which formed part of the Gertrud and Heno Plateaus, and sedimentation occurred in the Norwegian part of the Feda Graben farther to the north. During subsequent transgression, the southern part of the Feda Graben began to subside, and a succession of backstepping back-barrier and shoreface sediments, 90 m thick, was deposited. In the deep Tail End and Feda Grabens and the Salt Dome Province, sequence boundary SB2 is developed as a conformity, indicating that there was not a significant fall in relative sea level in these grabens, probably as a result of high subsidence rates. Backstepping lower shoreface sandstones overlie SB2 and show a gradual fining-upwards to offshore claystones that are referred to the Farsund Formation. On the plateaus, backstepping shoreface sandstones of sequence 2 are abruptly overlain by offshore claystones, indicating a sudden deepening and associated cessation of sand supply, probably caused by drowning of the sediment source areas on the Mandal, Inge and Mads Highs. During the Volgian, the Gertrud Plateau began to subside and became a graben. During the Late Kimmeridgian – Ryazanian, a long-term relative sea-level rise resulted in deposition of a thick succession of offshore claystones forming highstand and transgressive systems tracts on the Heno Plateau, and in the Gertrud, Feda and Tail End Grabens.

Event deposits in the Eastern Thermaikos Gulf and Kassandra Peninsula (Northern Greece): evidence of the 479 BC "Herodotus tsunami"

2019 ◽  
Vol 62 (2) ◽  
pp. 101-125
Author(s):  
Margret Mathes-Schmidt ◽  
Ioannis Papanikolaou ◽  
Klaus Reicherter ◽  
Aggelos Pallikarakis
Keyword(s):  
High Energy ◽  
Time Span ◽  
The South ◽  
Northern Greece ◽  
Reservoir Effect ◽  
Tsunami Waves ◽  
Vast Amount ◽  
The North ◽  
First Time ◽  
Bivalve Shells

Event deposits of high-energy waves in the Eastern Thermaikos Gulf and Kassandra Peninsula (Northern Greece) are investigated, and evidence for the 479 BC "Herodotus tsunami" is described for the first time. One of the first historical descriptions of tsunami waves and its effects on Persian troops near Potidaea in 479 BC was made by Herodotus. Sedimentary traces of tsunamis were investigated in cores from different areas from Angelochori in the north to the ruins of ancient Mende in the south (Kassandra peninsula). Evidence for one, locally two high-energy events, on the coasts of Chalkidiki is found. These layers are preserved in flat and lagoonal areas at least from 100 m of the present-day beach. Within ancient Mende, a high-energy layer was encountered. Besides a vast amount of ceramics, the layer also contains articulated bivalve shells. These were dated to a time span between 712 and 521 cal yrs BC by radiocarbon including a reservoir effect of 400 ± 40 years. Resulting ages resemble the time the tsunami mentioned by Herodotus in 479 BC. Deposits of a further event affecting the Thermaikos Gulf were dated between the 7 th to 10 th cent. AD.

The late Quaternary sedimentary record of Stave Lake, southwestern British Columbia

1992 ◽  
Vol 29 (9) ◽  
pp. 1997-2006 ◽  
Author(s):  
Robert Gilbert ◽  
Joseph R. Desloges
Keyword(s):  
Late Quaternary ◽  
Sediment Surface ◽  
Total Thickness ◽  
The South ◽  
Sedimentary Record ◽  
The Holocene ◽  
Acoustic Data ◽  
The North ◽  
Sediment Input ◽  
Fraser Valley

The postglacial sedimentary record of 59 km2 Stave Lake was investigated using 3.5 kHz subbottom profiles and cores from the sediment surface. The acoustic data show a thin cover of acoustically transparent sediment (unit 1) overlying bedrock or glacial sediment on the floor of the lake. Overlying acoustically stratified sediment is divided into unit 2, which thins from 28 m in the south of the lake to less than 12 m in the north, and unit 3, which thins from 20 m in the north to about 12 m in the south. Unit 1 is interpreted as resulting from deposition in a relatively quiet lacustrine or marine environment following retreat of Vashon glaciers about 13 ka ago. Unit 2 is ascribed to deposits of sediment in runoff to Stave Lake from the Sumas ice sheet in the Fraser Valley and connecting valleys to the Stave Basin. Following the retreat of the Sumas ice about 11 ka ago, deposition of unit 3 resulted almost entirely from sediment input from Stave River entering at the north end of the lake. Raising the lake in 1912 by damming for hydroelectric generation resulted in deposition of a thin but distinct marker horizon in the sediment, from which modern rates of accumulation averaging 3 mm/a are estimated. These are more than twice the average rates for the Holocene estimated from the total thickness of unit 3. The rates of sediment yield calculated from accumulation in Stave Lake are 4.5 × 105 kg∙km−2∙a−1 (modern) and less than 2 × 105 kg∙km−2∙a−1 (averaged over the Holocene).

Glacial and early postglacial lacustrine environment of a portion of northeastern Lake Ontario

1992 ◽  
Vol 29 (1) ◽  
pp. 63-75 ◽  
Author(s):  
Robert Gilbert ◽  
John Shaw
Keyword(s):  
Lake Ontario ◽  
Late Glacial ◽  
High Energy ◽  
Upper Great Lakes ◽  
Glacial Sediments ◽  
The North ◽  
Large Channel ◽  
Acoustic Facies ◽  
Short Time ◽  
Subglacial Meltwater

A deep channel in bedrock extending to more than 25 m below sea level occurs along the north shore of the otherwise uniformly shallow Kingston basin of Lake Ontario. Bathymetric and subbottom acoustic data are used to map the topography of the channel and to reconstruct its late glacial and postglacial sedimentary history. The results are interpreted as showing that the large channel and smaller channels nearby were created by high-velocity subglacial meltwater flow. Acoustic facies assemblages of sediments deposited in the channels record patchy deposition, or deposition followed by partial erosion, of glacial sediments on the bedrock of the channel floor, followed by deposition and episodic erosion of glaciolacustrine sediment in a high-energy, ice-proximal lake. Palaeoslope analysis confirms that the early Holocene low-water phase of Lake Ontario resulted in the development of a fluvial system in part of the channel. Water level was controlled by a sill at Kingston. Kingston basin, the Bay of Quinte, and possibly, for a short time, a much larger area of the upper Great Lakes drained through the channel. However, for most of the period, until it was flooded by the rising waters of Lake Ontario, the channel was occupied by a small river on a wide floodplain or it was flanked by broad marshes.

Late Glacial and Early Holocene Landscapes in Northern New England and Adjacent Areas of Canada

1985 ◽  
Vol 23 (3) ◽  
pp. 341-368 ◽  
Author(s):  
R. B. Davis ◽  
G. L. Jacobson
Keyword(s):  
New England ◽  
Late Glacial ◽  
The South ◽  
Individual Tree ◽  
Sea Levels ◽  
Vegetational Change ◽  
Closed Forest ◽  
Approximate Order ◽  
Paper Birch ◽  
Northern New England

The landscapes of northern New England and adjacent areas of Canada changed greatly between 14,000 and 9000 yr B.P.: deglaciation occurred, sea levels and shorelines shifted, and a vegetational transition from tundra to closed forest took place. Data from 51 14C-dated sites from a range of elevations were used to map ice and sea positions, physiognomic vegetational zones, and the spread of individual tree taxa in the region. A continuum of tundra-woodland-forest passed northeastward and northward without major hesitation or reversal. An increased rate of progression from 11,000 to 10,000 yr B.P. suggests a more rapid warming than in the prior 2000–3000 yr. Elevational gradients controlled the patterns of deglaciation and vegetational change. The earliest spread of tree taxa was via the lowlands of southern Vermont and New Hampshire, and along a coastal corridor in Maine. Only after 12,000 yr B.P. did the taxa spread northward through the rest of the area. Different tree species entered the southern part of the area at different times and continued their spread at different rates. The approximate order of arrival follows: poplars (13,000–12,000 yr B.P. in the south), spruces, paper birch, and jack pine, followed by balsam fir and larch, and possibly ironwood, ash, and elm, and somewhat later by oak, maple, white pine, and finally hemlock (10,000–9000 yr B.P. in the south).

Long-term Cyclic Variations of Prominences, Green and Red Coronae over Solar Cycles

2000 ◽  
Vol 179 ◽  
pp. 201-204
Author(s):  
Vojtech Rušin ◽  
Milan Minarovjech ◽  
Milan Rybanský
Keyword(s):  
Emission Lines ◽  
High Latitudes ◽  
Green Line ◽  
Solar Cycles ◽  
The South ◽  
Coronal Emission ◽  
Local Maxima ◽  
The North ◽  
Cyclic Variations

AbstractLong-term cyclic variations in the distribution of prominences and intensities of green (530.3 nm) and red (637.4 nm) coronal emission lines over solar cycles 18–23 are presented. Polar prominence branches will reach the poles at different epochs in cycle 23: the north branch at the beginning in 2002 and the south branch a year later (2003), respectively. The local maxima of intensities in the green line show both poleward- and equatorward-migrating branches. The poleward branches will reach the poles around cycle maxima like prominences, while the equatorward branches show a duration of 18 years and will end in cycle minima (2007). The red corona shows mostly equatorward branches. The possibility that these branches begin to develop at high latitudes in the preceding cycles cannot be excluded.

US and Russian policies and strategies in the Middle East: Iraq and Syria as a model

2019 ◽  
pp. 220
Author(s):  
Esraa Aladdin Noori ◽  
Nasser Zain AlAbidine Ahmed
Keyword(s):  
Middle East ◽  
East Asia ◽  
Balance Of Power ◽  
Western World ◽  
International Conflicts ◽  
The South ◽  
The West ◽  
The North ◽  
East Region ◽  
Middle East Region

The Russian-American relations have undergone many stages of conflict and competition over cooperation that have left their mark on the international balance of power in the Middle East. The Iraqi and Syrian crises are a detailed development in the Middle East region. The Middle East region has allowed some regional and international conflicts to intensify, with the expansion of the geopolitical circle, which, if applied strategically to the Middle East region, covers the area between Afghanistan and East Asia, From the north to the Maghreb to the west and to the Sudan and the Greater Sahara to the south, its strategic importance will seem clear. It is the main lifeline of the Western world.

Sign in / Sign up

Export Citation Format

Share Document