Proposed Younger Dryas glaciation of the eastern Scotian Shelf

1994 ◽  
Vol 31 (2) ◽  
pp. 401-417 ◽  
Author(s):  
Lewis H. King
Keyword(s):  
Younger Dryas ◽  
Shelf Area ◽  
Seismic Profiles ◽  
Scotian Shelf ◽  
Depositional History ◽  
Seismic Reflection Data ◽  
Outer Banks ◽  
Reflection Data ◽  
History Of ◽  
Subglacial Meltwater

A refined synthesis of the stratigraphy of the Scotian Shelf is presented, based on recently published borehole and seismic-reflection data and detailed correlation along high-resolution seismic profiles between the outer banks and the central basins.One of the new stratigraphic units of the outer bank region is of glacigenic origin and represents the last glacial event near the margin of the shelf. These deposits appear to be part of a morainal bank complex formed at a tidewater front. A Younger Dryas age is proposed for the glacial deposits, and the ice may have been widely distributed across the eastern Scotian Shelf. Evidence for the late glaciation is expressed in the central shelf area by an unconformity, which on the bank areas is associated with subglacial meltwater channels. 14C dates for the basin sediments of this region provide the most reliable chronology for the shelf stratigraphy.The origin of Sable Island is closely related to the depositional history of the moraine, and its surface has been modified by a Holocene transgressive event. A similar moraine formed on Banquereau but at greater depths.

scholarly journals Comparison between reprocessed seismic profiles: Seismologic and geologic data — A case study of the Colfiorito earthquake area

Geophysics ◽  
2006 ◽  
Vol 71 (2) ◽  
pp. B29-B40 ◽  
Author(s):  
Eusebio Stucchi ◽  
Francesco Mirabella ◽  
Maria Grazia Ciaccio
Keyword(s):  
Seismic Profile ◽  
Hydrocarbon Exploration ◽  
Normal Faults ◽  
Seismic Profiles ◽  
Epicentral Area ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Marche Region ◽  
History Of

Seismic reflection data are used to reconstruct the subsurface geologic structures below the Umbria-Marche region in Italy, a highly seismogenic area with a recent history of seismic activity (the 1997–1998 Colfiorito sequence). We reprocess three vibroseis seismic profiles (acquired in the early 1980s for hydrocarbon exploration) whose stacked sections were optimized for relatively deep oil targets. On the reprocessed seismic profile closest to the epicentral area, we construct the main reflectors to a depth of about 4 s (two-way time) and compare this interpretation with the available hypocenters of the 1997 earthquakes. The improvements in visualizing the shallow and deep reflections provide a better correlation between the reflectors and the observed surface structures as well as a better delineation of the basement-rock geometry. We find that part of the Colfiorito sequence is localized around some of the reflectors in the reflection profile, which we interpret as related to the active normal faults that outcrop at the surface.

scholarly journals Plio-Quaternary history of the Turkish coastal zone of the Enez-Evros Delta: NE Aegean Sea

2001 ◽  
Vol 2 (2) ◽  
pp. 95 ◽  
Author(s):  
B. ALPAR
Keyword(s):  
Late Pleistocene ◽  
Sand Dunes ◽  
Aegean Sea ◽  
Interglacial Period ◽  
Shelf Area ◽  
Sea Level Changes ◽  
Seismic Profiles ◽  
Alluvial Deposits ◽  
History Of ◽  
Quaternary History

The Enez-Evros Delta, NE Aegean Sea, is located in one the most important wetlands in the world with its sandy offshore islands, abandoned channel mouths, sand-dunes, shoals, marshlands, saline lagoons and saltpans. It comprises very well developed sedimentary units and a prodelta lying on an older submarine delta. The present day elevations of the middle-late Pleistocene marine terraces indicate a regional tectonic uplift in the area. Due to lack of geophysical and bore hole data and partly due to its strategic position, the structural and stratigraphic features of the submarine extension of the delta are not known in detail. In this paper, Plio-Quaternary history of this delta and its submarine part on the Turkish shelf was explored by using high-resolution shallow reflection seismic profiles. The delta is formed by the alluvial deposits of the Enez-Evros River and shaped by their interaction with the sea. It takes place in front of a large and protected ancient bay which was filled rapidly over millennia. The sediments in the plateau off the river are principally pro-deltaic with muddy areas near the river mouths changing to muddy sand further out. The sea-level changes in Plio-Quaternary were characterised by three different seismic stratigraphic units on the folded Miocene limestone basement. In the late Pleistocene, the shelf area over an Upper Miocene basement was flooded during the Riss-Würm interglacial period, exposed in the Würm glacial stage, and flooded once again during the Holocene transgression.

Crustal structure and surface zonation of the Canadian Appalachians: implications of deep seismic reflection data

1989 ◽  
Vol 26 (2) ◽  
pp. 305-321 ◽  
Author(s):  
François Marillier ◽  
Charlotte E. Keen ◽  
Glen S. Stockmal ◽  
Garry Quinlan ◽  
Harold Williams ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Surface Expression ◽  
Seismic Profiles ◽  
Crust And Upper Mantle ◽  
Seismic Reflection Data ◽  
Central Block ◽  
Reflection Data ◽  
Lower Crustal ◽  
Canadian Appalachians

In 1986, 1181 km of marine seismic reflection data was collected to 18–20 s of two-way traveltime in the Gulf of St. Lawrence area. The seismic profiles sample all major surface tectono-stratigraphic zones of the Canadian Appalachians. They complement the 1984 deep reflection survey northeast of Newfoundland. Together, the seismic profiles reveal the regional three-dimensional geometry of the orogen.Three lower crustal blocks are distinguished on the seismic data. They are referred to as the Grenville, Central, and Avalon blocks, from west to east. The Grenville block is wedge shaped in section, and its subsurface edge follows the form of the Appalachian structural front. The Grenville block abuts the Central block at mid-crustal to mantle depths. The Avalon block meets the Central block at a steep junction that penetrates the entire crust.Consistent differences in the seismic character of the Moho help identify boundaries of the deep crustal blocks. The Moho signature varies from uniform over extended distances to irregular with abrupt depth changes. In places the Moho is offset by steep reflections that cut the lower crust and upper mantle. In other places, the change in Moho elevation is gradual, with lower crustal reflections following its form. In all three blocks the crust is generally highly reflective, with no distinction between a transparent upper crust and reflective lower crust.In general, Carboniferous and Mesozoic basins crossed by the seismic profiles overlie thinner crust. However, a deep Moho is found at some places beneath the Carboniferous Magdalen Basin.The Grenville block belongs to the Grenville Craton; the Humber Zone is thrust over its dipping southwestern edge. The Dunnage Zone is allochthonous above the opposing Grenville and Central blocks. The Gander Zone may be the surface expression of the Central block or may be allochthonous itself. There is a spatial analogy between the Avalon block and the Avalon Zone. Our profile across the Meguma Zone is too short to seismically distinguish this zone from the Avalon Zone.

scholarly journals Basal and Frontal Accretion Processes versus BSR Characteristics along the Chilean Margin

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
I. Vargas-Cordero ◽  
U. Tinivella ◽  
F. Accaino ◽  
F. Fanucci ◽  
M. F. Loreto ◽  
...  
Keyword(s):  
Normal Faults ◽  
Seismic Profiles ◽  
Seismic Reflection Data ◽  
Sediment Bed ◽  
Reflection Data ◽  
Extensional Tectonic ◽  
Bottom Simulating Reflectors ◽  
High Fluid ◽  
Multichannel Seismic Reflection Data ◽  
Accretionary Prisms

Multichannel seismic reflection data recorded between Itata (36°S) and Coyhaique offshores (43°S) were processed to obtain seismic images. Analysis of the seismic profiles revealed that weak and discontinuous bottom simulating reflectors were associated to basal accretion processes, while strong and continuous bottom simulating reflectors were associated to frontal accretion processes. This can be explained considering that during basal accretion processes, extensional tectonic movements due to uplifting can favour fluid escapes giving origin to weaker and most discontinuous bottom simulating reflectors. During frontal accretion processes (folding and thrusting), high fluid circulation and stable tectonic conditions however can be responsible of stronger and most continuous bottom simulating reflectors. Along the Arauco-Valdivia offshores, steep accretionary prisms, normal faults, slope basins, and thicker underplated sediment bed were associated to basal accretion, while along the Itata, Chiloe and Coyhaique offshores, small accretionary prisms, folding, and thinner underplated sediment bed were associated to frontal accretion.

scholarly journals An extended history of high-amplitude lake-level changes in tectonically active Lake Issyk-Kul (Kyrgyzstan), as revealed by high-resolution seismic reflection data

2016 ◽  
Author(s):  
A. C. Gebhardt ◽  
Lieven Naudts ◽  
Lies De Mol ◽  
Jan Klerkx ◽  
Kanatbek Abdrakhmatov ◽  
...  
Keyword(s):  
Lake Level ◽  
Circulation Pattern ◽  
High Amplitude ◽  
Lake Levels ◽  
Seismic Profiles ◽  
Seismic Reflection Data ◽  
Air Masses ◽  
Siberian High ◽  
Lake Level Changes ◽  
Reflection Data

Abstract. A total of 84 seismic profiles mainly from the western and eastern deltas of Lake Issyk-Kul were used to identify lake-level changes. Seven stratigraphic sequences were identified each containing a series of delta lobes that were formed during former lake-level stillstands. Lake-level has experienced at least four cycles of stepwise fall and rise of 400 m or more. These fluctuations were mainly caused by past changes in the atmospheric circulation pattern during the past. During periods of low lake levels, the Siberian High likely was strong, bringing dry air masses from the Mongolian steppe. The strong Siberian High blocked the mid-latitude Westerlies. During periods of high lake levels, the Siberian High must have been weaker or displaced, and the mid-latitude Westerlies could bring moister air masses from the Mediterranean and North Atlantic regions.

CASE HISTORY OF WILD GOOSE GAS FIELD, BUTTE COUNTY, CALIFORNIA

Geophysics ◽  
1954 ◽  
Vol 19 (3) ◽  
pp. 509-516 ◽  
Author(s):  
Wallace L. Matjasic
Keyword(s):  
Cross Sections ◽  
Seismic Reflection ◽  
Upper Cretaceous ◽  
Gas Field ◽  
Contour Map ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
History Of ◽  
Further Development ◽  
Wild Goose

The discovery well of the Wild Goose gas field was drilled and completed in 1951 on a structure located by a reflection seismograph survey conducted in 1950. An additional seismograph survey was made subsequent to discovery to define the structure better for further development. The illustrations include two seismic cross sections, a contour map based on the original seismic reflection data, an aeromagnetic map, a structure contour map, and an electric log of the discovery well. The producing sands are in an interval between the Forbes shale of Upper Cretaceous age and the overlying Capay shale of Eocene age.

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