Graphic correlation of Middle Ordovician graptolite shale, southern Appalachians: An approach for examining the subsidence and migration of a Taconic foreland basin

1996 ◽  
Vol 108 (3) ◽  
pp. 355-371 ◽  
Author(s):  
Stanley C. Finney ◽  
Barbara J. Grubb ◽  
Robert D. Hatcher
Keyword(s):  
Foreland Basin ◽  
Southern Appalachians ◽  
Middle Ordovician ◽  
And Migration

Basin development and inversion at the Appalachian structural front, Port au Port Peninsula, western Newfoundland Appalachians

1993 ◽  
Vol 30 (9) ◽  
pp. 1759-1772 ◽  
Author(s):  
John W. F. Waldron ◽  
Glen S. Stockmal ◽  
Randolph E. Corney ◽  
Sheila R. Stenzel
Keyword(s):  
Foreland Basin ◽  
Fault Scarp ◽  
Late Ordovician ◽  
The West ◽  
Western Basin ◽  
Middle Ordovician ◽  
Platform Carbonates ◽  
Palinspastic Restoration ◽  
And Inversion ◽  
Basin Boundaries

In the Humber Zone of the Newfoundland Appalachians, Cambro-Ordovician shelf and foreland basin successions are affected by Middle Ordovician (Taconian orogeny) and Devonian (Acadian orogeny) deformation. On Port au Port Peninsula the presence of the Late Ordovician to Late Silurian Long Point – Clam Bank succession allows these episodes to be separated. The Taconian foreland basin stratigraphy on Port au Port Peninsula is highly variable. On the west coast, platform carbonates are overlain by megaconglomerates of the Cape Cormorant Formation, which record progressive exposure of 1 km of the platform succession. The conglomerates are restricted to a narrow zone, consistent with derivation from a fault scarp originally immediately west of the outcrops (in palinspastic restoration). Farther east, at Victors Brook, the Cape Cormorant Formation is absent, but the overlying, almost undeformed Goose Tickle Group contains conglomerate derived both from the upper part of the platform succession and from the Taconian Humber Arm Allochthon. Southeast of Victors Brook, the top of the platform is overlain directly by scaly shales and mélange of the Humber Arm Allochthon, which includes deformed equivalents of the foreland basin succession. The distribution of conglomeratic units, the presence and configuration of faults, and the preservation of the Goose Tickle Group in the Victors Brook area imply that a fault-bounded basin developed in advance of the Humber Arm Allochthon during the Taconian orogeny. This basin is interpreted to have resulted from flexural extension of North American lithosphere. The close spatial coincidence between later Acadian structures and the Taconian basin boundaries implies that the basin-bounding faults were reactivated as thrusts and reverse faults, and that the basin underwent inversion during Acadian thrusting. The western basin-bounding fault, modified by the development of a "short cut" thrust, developed into the present-day Round Head thrust.

Large-scale liquefaction and fluidization in the Cap Chat Mélange, Quebec Appalachians

1998 ◽  
Vol 35 (12) ◽  
pp. 1408-1422 ◽  
Author(s):  
Pierre A Cousineau
Keyword(s):  
Large Scale ◽  
Foreland Basin ◽  
Main Mechanism ◽  
Northern Limit ◽  
Middle Ordovician ◽  
Surrounding Matrix ◽  
Tectonic Processes ◽  
Lower Ordovician ◽  
South Shore ◽  
St Lawrence River

The Cap Chat Mélange crops out discontinuously for 200 km along the south shore of the St. Lawrence River in the Gaspé Peninsula. It is located just south of Logan's line, the northern limit of the Humber zone with the Taconian foreland basin. This mélange is composed of dismembered rocks of the adjacent formations, in particular the Lower Ordovician Rivière Ouelle and Middle Ordovician Tourelle formations, with lesser contributions by the Middle Ordovician Des Landes and the Cambrian Orignal formations. Blocks in the mélange vary in size from a few centimetres to several kilometres, with well-preserved internal stratigraphy in the larger blocks. The distribution of blocks is not uniform and the composition of the surrounding matrix changes with corresponding changes in block composition. Tectonic processes, mostly extensional and compressional faulting, are responsible for some of the chaotic aspects of the mélange. However, the main mechanism was as follows: (i) large-scale liquefaction of the mudstone-rich Rivière Ouelle Formation, (ii) sinking with consequent dismembering of the Tourelle Formation into this underlying weakened Rivière Ouelle Formation, and (iii) fluidization of the lowermost sand beds of the Tourelle Formation resulting in abundant sandstone sills and dikes in the Rivière Ouelle Formation.

scholarly journals The Natih Petroleum System of North Oman

GeoArabia ◽  
1999 ◽  
Vol 4 (2) ◽  
pp. 157-180 ◽  
Author(s):  
Jos M.J. Terken
Keyword(s):  
Foreland Basin ◽  
Petroleum System ◽  
Source Rocks ◽  
Trapping Efficiency ◽  
Structural Deformation ◽  
Hydrocarbon Potential ◽  
Lateral Migration ◽  
Efficient System ◽  
Giant Fields ◽  
And Migration

ABSTRACT The Cretaceous Natih petroleum system is one of the smaller petroleum systems in Oman, measuring only some 20,000 square kilometers in areal extent. Resource volumes of oil initially in-place, however, are significant and amount to 1.3x109 cubic meters (equivalent to 8.2 billion barrels). Most of the recoverable oil is concentrated in two giant fields that were discovered in the early 1960s. Since that prolific time no new major discoveries have been made, except some marginally economic accumulations in the early 1980s. To evaluate the remaining hydrocarbon potential of the system, the oil kitchen was mapped and its generation and migration histories modeled and integrated with the regional setting to outline the geographical and stratigraphical extent of the petroleum system. The volume of liquid hydrocarbons generated by Natih source rocks was calculated and compared to the estimated oil-in-place to determine the generation-trapping efficiency of the petroleum system. Some 100x109 cubic meters of source rock is currently mature and produced a cumulative volume of 14x109 cubic meters (88 billion barrels) oil. Of this volume 9% has actually been discovered and 0.25x109 cubic meters (1.57 billion barrels) are currently booked as recoverable reserves, equivalent to 1.8% of the total generated volume. Both percentages classify the Natih petroleum system as the most efficient system in Oman. This extreme efficiency results from several factors, such as: (1) modest structural deformation in the foreland basin, which permits lateral migration to remain the dominant style; (2) abundant and uninterrupted access to oil charge from an active kitchen in the foreland basin; and (3) excellent intra-formational source rocks, which is retained by thick Fiqa shales. Most structural prospects have been tested in four decades of exploration. The remaining hydrocarbon potential is anticipated to exist mainly in stratigraphic traps in Fiqa turbidites in the foreland basin, and truncation traps across the northern flank of the peripheral bulge.

scholarly journals Declining importance of trilobites in Ordovician nearshore communities: displacement or dilution?

1992 ◽  
Vol 6 ◽  
pp. 310-310
Author(s):  
Stephen R. Westrop ◽  
James V. Tremblay ◽  
Ed Landing
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Environmental Changes ◽  
General Pattern ◽  
Foreland Basin ◽  
Middle Ordovician ◽  
Diversity Gradient ◽  
Nearshore Environments ◽  
Community Evolution ◽  
Northern United States

Declining importance of trilobites was a key feature of Ordovician community “evolution”. Previous work has shown that replacement of trilobite-dominated communities by mollusc- and brachiopod-dominated communities was diachronous, occurring initially in nearshore settings. The processes responsible for these changes remain unclear, although many previous discussions have invoked some form of displacement of dominants of one community by those of another.New data from more than thirty large collections made from nearshore facies at five localities in Canada and the northern United States indicate that, in this setting, trilobite species diversity maintained a constant low level (mean and mode of 3 species) between the Early Upper Cambrian (Marjuman) and the Late Middle Ordovician (Blackriveran). Reorganization of nearshore communites proceeded by addition of new elements, especially molluscs, from the Late Cambrian (Sunwaptan) onwards. Decline in the relative importance of trilobites was a case of dilution as species of new clades accumulated, rather than actual displacement. Trilobites appear to have been passive bystanders in Ordovician nearshore community “evolution”. Towards the end of the Ordovician, trilobites vacated nearshore environments in the Appalachian region. However, this appears to be related to environmental changes associated with progradation of clastic wedges during the development of the Taconic foreland basin.A process of dilution may at least partly explain the offshore retreat of trilobite-dominated assemblages during the Ordovician. Offshore trilobite assemblages reached much greater species diversity than those of nearshore settings, so that their dilution via the addition of species of newly radiating clades would have proceeded more slowly. That is, trilobite-dominated paleocommunities may have persisted into the Ordovician in the outer shelf simply because this was the region in which, historically, they attained maximum species richness. Moreover, given the existence of a general pattern of increasing total species diversity of communities from nearshore to offshore sites, the tendency for newly radiating clades to attain maximum species richness offshore is not surprising: they are merely conforming to a general, environmentally-related diversity gradient that has existed throughout the Phanerozoic.

Inversion of Taconian extensional structures during Paleozoic orogenesis in western Newfoundland

2018 ◽  
Vol 470 (1) ◽  
pp. 311-336 ◽  
Author(s):  
Shawna E. White ◽  
John W. F. Waldron
Keyword(s):  
Long Range ◽  
Foreland Basin ◽  
Passive Margin ◽  
Normal Faults ◽  
Middle Ordovician ◽  
Iapetus Ocean ◽  
Thrust Belts ◽  
Wilson Cycle ◽  
Flexural Bulge ◽  
Extensional Structures

AbstractWest Newfoundland was critical in developing the Wilson Cycle concept. Neoproterozoic rifting established a passive margin adjacent to the Iapetus Ocean. Ordovician (Taconian) arc–continent collision emplaced ophiolites and the thin-skinned Humber Arm Allochthon. Subsequent Devonian (Acadian) ocean closure produced basement-cutting thrust faults that control the present-day distribution of units. New mapping, and aeromagnetic and seismic interpretation, around Parsons Pond enabled the recognition of structures in poorly exposed areas.Following Cambrian to Middle Ordovician passive-margin deposition, Taconian deformation produced a flexural bulge unconformity. Subsequent extensional faults shed localized conglomerate into the foreland basin. The Humber Arm Allochthon contains a series of stacked and folded duplexes, typical of thrust belts. To the east, the Parsons Pond Thrust has transported shelf and foreland-basin units c. 8 km westwards above the allochthon. The Long Range Thrust shows major topographical expression but <1 km offset. Stratigraphic relationships indicate that most thrusts originated as normal faults, active during Neoproterozoic rifting, and subsequently during Taconian flexure. Devonian continental collision inverted the Parsons Pond and Long Range thrusts. Basement-cored fault-propagation folds in Newfoundland are structurally analogous to basement uplifts in other orogens, including the Laramide Orogen in western USA. Similar deep-seated inversion structures may extend through the northern Appalachians.

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