scholarly journals Late Quaternary sea level, isostatic response, and sediment dispersal along the Queen Charlotte fault

Geosphere ◽  
2021 ◽  
Author(s):  
J. Vaughn Barrie ◽  
H. Gary Greene ◽  
Kim W. Conway ◽  
Daniel S. Brothers
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Shelf Break ◽  
Fault System ◽  
Haida Gwaii ◽  
Storm Activity ◽  
Submarine Channels ◽  
Southeast Alaska ◽  
Short Period ◽  
Level Lowering

The active Pacific margin of the Haida Gwaii and southeast Alaska has been subject to vigorous storm activity, dramatic sea-level change, and active tectonism since glacial times. Glaciation was minimal along the western shelf margin, except for large ice streams that formed glacial valleys to the shelf break between the major islands of southeast Alaska and Haida Gwaii. Upon deglaciation, sediment discharge was extensive, but it terminated quickly due to rapid glacial retreat and sea-level lowering with the development of a glacio-iso­static forebulge, coupled with eustatic lowering. Glacial sedimentation offshore ended soon after 15.0 ka. The shelf became emergent, with sea level lowering by, and possibly greater than, 175 m. The rapid transgression that followed began sometime before 12.7 ka off Haida Gwaii and 12.0 ka off southeast Alaska, and with the extreme wave-dominated environment, the unconsolidated sediment that was left on the shelf was effectively removed. Temperate carbonate sands make up the few sediment deposits presently found on the shelf. The Queen Charlotte fault, which lies just below the shelf break for most of its length, was extensively gullied during this short period of significant sed­iment discharge, when sediment was transported though the glacial valleys and across the narrow shelf through fluvial and submarine channels and was deposited offshore as sea level dropped. The Queen Charlotte fault became the western terminus of the glacio-isostatic forebulge, with the fault acting as a hinged flap taking up the uplift and collapse along the fault of 70+ m. This may have resulted in the development of the distinctive fault valley that presently acts as a very linear channel pathway for sediment throughout the fault system.

Submerged landscapes of the eastern Adriatic – from the river across the lake all the way to the sea

2021 ◽  
Author(s):  
Slobodan Miko ◽  
Keyword(s):  
Sea Level ◽  
Environmental Changes ◽  
Late Quaternary ◽  
River Estuary ◽  
Integrated System ◽  
Submarine Channels ◽  
Side Scan Sonar ◽  
Sedimentary Sequences ◽  
Marine Sedimentation ◽  
Geophysical Surveys

<p>Submerged paleolandscapes constitute records of long-term paleoenvironmental change, climate, and sea level. To date, there is a very limited knowledge concerning the submerged karst paleolandscapes of the eastern Adriatic coast and the Late Quaternary sedimentary sequences along the eastern part of the Mid Adriatic Deep (MAD). We aim to improve this through the project “Sediments between source and sink during a Late Quaternary eustatic cycle: The Krka and the Mid Adriatic Deep System” (QMAD). The QMAD project supports multidisciplinary research by application of the high-resolution geophysical surveys (multibeam, side-scan sonar and sub-bottom profiler), in combination with sedimentological, petrophysical, geochemical (trace elements and isotopes), micropaleontological (ostracod and foraminifera), mineralogical and aDNA techniques. This suite of analyses will enable tracking of the paleoenvironmental evolution from fluvial/lake to deeper marine environments, on a short transect less than 100 km in length (Lake Prokljan in the Krka River estuary to the eastern part of MAD). The submerged Late Pleistocene and Holocene environments that occur include isolation basins, lagoons, deltas, estuaries, submarine channels and shelf. The continuous marine sedimentation during the Late Quaternary is investigated in the MAD. In the case of the central part of the eastern side of the Adriatic Sea (Krka catchment - MAD) these different environments compose an integrated system; thus, they can’t be analysed separately. The main goals of this project fill the existing gaps in understanding of the climatic and environmental changes, including sea-level related landscape changes and their interplay during the Late Quaternary eustatic cycle. More data on the Pleistocene environments, especially from the region of Krka estuary that was land during the Last Glacial Maximum (LGM), will complete the picture of the evolution and environmental adaptation of Paleolithic humans and their relationship with vegetation changes. Attention is also paid to potential anthropogenic environments, recent sedimentation rates, landscape features and artefacts. All results of the multi-proxy approach applied in this project will eventually be merged into a comprehensive Late Quaternary paleoenvironmental and paleoclimatic reconstruction of the eastern Adriatic landscapes that contribute to the understanding of these changes in the Mediterranean region.</p>

scholarly journals Marine Geology of the Turnagain Area

2021 ◽  
Author(s):  
◽  
Keith Brian Lewis
Keyword(s):  
Continental Shelf ◽  
Sea Level ◽  
Continental Slope ◽  
Late Quaternary ◽  
Outer Part ◽  
Shelf Break ◽  
Seismic Profiles ◽  
Sediment Samples ◽  
Near Shore ◽  
Upper Slope

<p>The Turnagain Area covers the continental shelf and slope off the east coast of North Island, New Zealand between Napier and Castlepoint. Its late Quaternary stratigraphy, tectonic history, sedimentation and foraminiferal distribution are described with the aid of continuous seismic profiles, sediment samples and cores. Results are presented in seven papers and a chart. The first three papers deal mainly with sub-bottom layers revealed by continuous seismic profiles; the next three papers describe dried sediment samples and cores and the last paper is a study of foraminifera in alcohol-preserved sediment samples. The topics discussed in each of the seven papers are as follows: 1. stratigraphy, sedimentation rates and origin of present topography on the continental shelf and upper slope; 2. rates of tectonic processes; 3. slumping; 4. distribution of sediments; 5. ages of indurated sediments; 6. ash horizons and rates of deposition on the lower part of the continental slope. 7. the distribution of living and dead foraminifera. The chart shows bathymetry and nature of sediment at the seabed. The sediments beneath the sea have been folding since Miocene times in the same way as marine sediments on the adjacent land. On the seabed anticlinal crests are preserved as ridges and banks and synclines form depressions. The present land area is rising and much of the seabed is sinking; the zero isobase between then is situated on the inner continental shelf. It has been at about the same position throughout Late Quaternary times, being always close to the dividing line between net erosion and net deposition. Rates of tilting have ranged from 2 to 36 microdegrees/thousand years and rates of vertical movement from +1.7 to -1.5 m/thousand years. Seaward of the zero isobase the continental shelf and upper slope has been built upwards and outwards by prisms of sediment, each prism representing a phase either of low sea level or of high sea level. Prisms deposited during periods of glacially lowered sea level are at their thickest beneath the upper slope; prisms deposited during periods of relatively high sea level are at their thickest beneath the continental shelf. Parts of the youngest prism on the upper slope have slumped on gradients as low as 1 [degree]. The topography and sediments formed during the last 20 thousand years have received the most attention. The present continental shelf if a composite feature. The inner part has been formed by wave-planation of hard rock near shore and deposition of the latest prism of sediment offshore. The outer part and the shelf break were formed by wave-planation and by deposition during the last low sea level about 20 thousand years ago. At that time the shelf break ranged in depth from about 40m to about 70m, being shallowest where eroded into soft sediment and deepest where deposited beyond the seaward edge of erosion. In adjacent areas the shelf break was probably formed at depths of less than 20m being eroded into hard rock. The inner part of the wave-planed surface formed at that time is now deeply buried by the latest prism of sediment but the outer part is covered by only a thin veneer. The outer shelf is still essentially a drowned low sea level feature. At the thickest part of the prism on the mid continental shelf, rates of deposition above an 8 thousand year old seismic reflector range from about 1 to about 4 m/thousand years, being most rapid south of major rivers. Rates are too slow to be measured at some places near the shelf break and at ridges on the continental slope. In depressions on the continental slope, sedimentation rates are indicated by the depth of the 3.4 thousand year old Waimihia ash and range from 0.36 m/thousand years in a depression relatively near land to 0.02 m/thousand years in the depression furthest from land. Sediments range from fine sand near shore to clayey fine silt on the lower slope. Many sediments are bimodal because they were deposited as a mixture of floculated and unfloculated grains. Rapidly deposited sediment on the continental shelf is predominantly detrital sand and silt; slowly deposited sediment near the shelf break and on ridges consists mostly of volcanic ash, foraminifera, and glauconite Muddy sediment in continental slope depressions contains sandy turbidite layers. Different environments are characterised by sediment types and foraminiferal faunas that can be matched in Tertiary Rocks.</p>

scholarly journals Marine Geology of the Turnagain Area

2021 ◽  
Author(s):  
◽  
Keith Brian Lewis
Keyword(s):  
Continental Shelf ◽  
Sea Level ◽  
Continental Slope ◽  
Late Quaternary ◽  
Outer Part ◽  
Shelf Break ◽  
Seismic Profiles ◽  
Sediment Samples ◽  
Near Shore ◽  
Upper Slope

<p>The Turnagain Area covers the continental shelf and slope off the east coast of North Island, New Zealand between Napier and Castlepoint. Its late Quaternary stratigraphy, tectonic history, sedimentation and foraminiferal distribution are described with the aid of continuous seismic profiles, sediment samples and cores. Results are presented in seven papers and a chart. The first three papers deal mainly with sub-bottom layers revealed by continuous seismic profiles; the next three papers describe dried sediment samples and cores and the last paper is a study of foraminifera in alcohol-preserved sediment samples. The topics discussed in each of the seven papers are as follows: 1. stratigraphy, sedimentation rates and origin of present topography on the continental shelf and upper slope; 2. rates of tectonic processes; 3. slumping; 4. distribution of sediments; 5. ages of indurated sediments; 6. ash horizons and rates of deposition on the lower part of the continental slope. 7. the distribution of living and dead foraminifera. The chart shows bathymetry and nature of sediment at the seabed. The sediments beneath the sea have been folding since Miocene times in the same way as marine sediments on the adjacent land. On the seabed anticlinal crests are preserved as ridges and banks and synclines form depressions. The present land area is rising and much of the seabed is sinking; the zero isobase between then is situated on the inner continental shelf. It has been at about the same position throughout Late Quaternary times, being always close to the dividing line between net erosion and net deposition. Rates of tilting have ranged from 2 to 36 microdegrees/thousand years and rates of vertical movement from +1.7 to -1.5 m/thousand years. Seaward of the zero isobase the continental shelf and upper slope has been built upwards and outwards by prisms of sediment, each prism representing a phase either of low sea level or of high sea level. Prisms deposited during periods of glacially lowered sea level are at their thickest beneath the upper slope; prisms deposited during periods of relatively high sea level are at their thickest beneath the continental shelf. Parts of the youngest prism on the upper slope have slumped on gradients as low as 1 [degree]. The topography and sediments formed during the last 20 thousand years have received the most attention. The present continental shelf if a composite feature. The inner part has been formed by wave-planation of hard rock near shore and deposition of the latest prism of sediment offshore. The outer part and the shelf break were formed by wave-planation and by deposition during the last low sea level about 20 thousand years ago. At that time the shelf break ranged in depth from about 40m to about 70m, being shallowest where eroded into soft sediment and deepest where deposited beyond the seaward edge of erosion. In adjacent areas the shelf break was probably formed at depths of less than 20m being eroded into hard rock. The inner part of the wave-planed surface formed at that time is now deeply buried by the latest prism of sediment but the outer part is covered by only a thin veneer. The outer shelf is still essentially a drowned low sea level feature. At the thickest part of the prism on the mid continental shelf, rates of deposition above an 8 thousand year old seismic reflector range from about 1 to about 4 m/thousand years, being most rapid south of major rivers. Rates are too slow to be measured at some places near the shelf break and at ridges on the continental slope. In depressions on the continental slope, sedimentation rates are indicated by the depth of the 3.4 thousand year old Waimihia ash and range from 0.36 m/thousand years in a depression relatively near land to 0.02 m/thousand years in the depression furthest from land. Sediments range from fine sand near shore to clayey fine silt on the lower slope. Many sediments are bimodal because they were deposited as a mixture of floculated and unfloculated grains. Rapidly deposited sediment on the continental shelf is predominantly detrital sand and silt; slowly deposited sediment near the shelf break and on ridges consists mostly of volcanic ash, foraminifera, and glauconite Muddy sediment in continental slope depressions contains sandy turbidite layers. Different environments are characterised by sediment types and foraminiferal faunas that can be matched in Tertiary Rocks.</p>

LATE QUATERNARY SEA-LEVEL HIGHSTANDS OF THE MID-ATLANTIC US COASTAL PLAIN AND SUB-ORBITAL VARIABILITY WITH IMPLICATIONS FOR ICE SHEET SENSITIVITY

2016 ◽  
Author(s):  
Robert K. Poirier ◽  
◽  
Thomas M. Cronin ◽  
Thomas M. Cronin ◽  
Miriam E. Katz ◽  
...  
Keyword(s):  
Sea Level ◽  
Coastal Plain ◽  
Late Quaternary ◽  
Ice Sheet

scholarly journals Spatial distribution of water level impact to back-barrier bays

2018 ◽  
Author(s):  
Alfredo L. Aretxabaleta ◽  
Neil K. Ganju ◽  
Zafer Defne ◽  
Richard P. Signell
Keyword(s):  
Water Level ◽  
Sea Level ◽  
Water Levels ◽  
Analytical Models ◽  
Barnegat Bay ◽  
Sea Level Fluctuations ◽  
Flooding Hazard ◽  
Short Period ◽  
Inlet Geometry ◽  
Spatial Estimates

Abstract. Water level in semi-enclosed bays, landward of barrier islands, is mainly driven by offshore sea level fluctuations that are modulated by bay geometry and bathymetry, causing spatial variability in the ensuing response (transfer). Local wind setup can have a secondary role that depends on wind speed, fetch, and relative orientation of the wind direction and the bay. Inlet geometry and bathymetry primarily regulate the magnitude of the transfer between open ocean and bay. Tides and short-period offshore oscillations are more damped in the bays than longer-lasting offshore fluctuations, such as storm surge and sea level rise. We compare observed and modeled water levels at stations in a mid-Atlantic bay (Barnegat Bay) with offshore water level proxies. Observed water levels in Barnegat Bay are compared and combined with model results from the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system to evaluate the spatial structure of the water level transfer. Analytical models based on the dimensional characteristics of the bay are used to combine the observed data and the numerical model results in a physically consistent approach. Model water level transfers match observed values at locations inside the Bay in the storm frequency band (transfers ranging from 70–100 %) and tidal frequencies (10–55 %). The contribution of frequency-dependent local setup caused by wind acting along the bay is also considered. The approach provides transfer estimates for locations inside the Bay where observations were not available resulting in a complete spatial characterization. The approach allows for the study of the Bay response to alternative forcing scenarios (landscape changes, future storms, and rising sea level). Detailed spatial estimates of water level transfer can inform decisions on inlet management and contribute to the assessment of current and future flooding hazard in back-barrier bays and along mainland shorelines.

scholarly journals Late Quaternary Landscape Dynamics at the La Spezia Gulf (NW Italy): A Multi-Proxy Approach Reveals Environmental Variability within a Rocky Embayment

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 427
Author(s):  
Veronica Rossi ◽  
Alessandro Amorosi ◽  
Marco Marchesini ◽  
Silvia Marvelli ◽  
Andrea Cocchianella ◽  
...  
Keyword(s):  
Sea Level ◽  
Environmental Variability ◽  
Late Quaternary ◽  
Landscape Dynamics ◽  
Last Interglacial ◽  
Core Depth ◽  
Coastal Bay ◽  
Nw Italy ◽  
Global Sea Level ◽  
Geomorphological Features

The Gulf of La Spezia (GLS) in Northwest Italy is a rocky embayment with low fluvial influence facing the Mediterranean Sea. Past landscape dynamics were investigated through a multi-proxy, facies-based analysis down to a core depth of 30 m. The integration of quantitative ostracod, foraminifera, and pollen analyses, supported by radiocarbon ages, proved to be a powerful tool to unravel the late Quaternary palaeoenvironmental evolution and its forcing factors. The complex interplay between relative sea-level (RSL), climatic changes, and geomorphological features of the embayment drove four main evolution phases. A barrier–lagoon system developed in response to the rising RSL of the Late Pleistocene (likely the Last Interglacial). The establishment of glacial conditions then promoted the development of an alluvial environment, with generalised erosion of the underlying succession and subsequent accumulation of fluvial strata. The Holocene transgression (dated ca. 9000 cal year BP) caused GLS inundation and the formation of a low-confined lagoon basin, which rapidly turned into a coastal bay from ca. 8000 cal year BP onwards. This latter environmental change occurred in response to the last Holocene stage of global sea-level acceleration, which submerged a morphological relief currently forming a drowned barrier-island complex in the embayment.

Late Quaternary sea-level and tectonic changes in northeast Fiji

2002 ◽  
Vol 187 (3-4) ◽  
pp. 299-311 ◽  
Author(s):  
Patrick D Nunn ◽  
Cliff Ollier ◽  
Geoffrey Hope ◽  
Peter Rodda ◽  
Akio Omura ◽  
...  
Keyword(s):  
Sea Level ◽  
Late Quaternary
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