Shallow-Water Stromatactis Mud-Mounds on a Middle Ordovician Foreland Basin Platform, Western Newfoundland

2009 ◽  
pp. 125-149 ◽  
Author(s):  
S. R. Stenzel ◽  
N. P. James
Keyword(s):  
Shallow Water ◽  
Foreland Basin ◽  
Mud Mounds ◽  
Middle Ordovician

scholarly journals The Sjælland Fjelde Formation: a new Ordovician formation from eastern North Greenland

1986 ◽  
Vol 132 ◽  
pp. 27-37
Author(s):  
J.R Ineson ◽  
J.S Peel ◽  
M.P Smith
Keyword(s):  
Shallow Water ◽  
North West ◽  
Middle Ordovician ◽  
The North ◽  
New Formation ◽  
North Greenland

The name Sjælland Fjelde Formation is introduced for a varied sequence of shallow-water platform dolomites and dolomitic limestones, about 105 m in thickness, in Kronprins Christian Land, eastern North Greenland. The new formation lies between the previously described Wandel Valley and Børglum River Formations. Conodont faunas indicate that the Sjælland Fjelde Formation is of Middle to earliest Late Whiterockian (early Middle Ordovician) age and that it can be eorrelated with the upper part of the Wandel Valley Formation of Peary Land to the north-west.

Bivalves from the Innviertel Group of Allerding in the North Alpine Foreland Basin (lower Miocene, Upper Austria)

2020 ◽  
Vol 297 (1) ◽  
pp. 47-100
Author(s):  
Oleg Mandic ◽  
Simon Schneider ◽  
Mathias Harzhauser ◽  
Wolfgang Danninger
Keyword(s):  
Shallow Water ◽  
Time Window ◽  
Foreland Basin ◽  
Migration Route ◽  
Central Paratethys ◽  
Seagrass Meadows ◽  
The North ◽  
North Alpine Foreland Basin ◽  
Alpine Foreland ◽  
Alpine Foreland Basin

During the Ottnangian (Burdigalian, early Miocene), the North Alpine Foreland Basin operated as a sea-way connecting the Central Paratethys Sea with the Rhône Basin in the Western Mediterranean. Within this short time window, an intensive faunal exchange between the two paleo-biogeographic units occurred, which is reflected in macrofossil assemblages. The extraordinarily rich fossil record of the study site, Allerding, located in the westernmost Central Paratethys, provides valuable insights into the composition and origins of the bivalve fauna colonizing the marine gateway. The site documents the early Ottnangian marine transgression over deeply weathered crystalline basement, grading from fossil bearing shallow water clay and sand into the open marine "Schlier" facies of the Ottnang Formation. Despite considerable taphonomic overprint including aragonite leaching and mechanical abrasion of bivalve shells under turbulent shallow-water conditions, a total of 46 species are recorded, including two new species (Lima allerdingensis n. sp. and Astarte danningeri n. sp.). The dominance of suspension feeders, and the presence of several deposit feeders and chemosymbiotic taxa point to well diversified inshore settings, including low intertidal mudflats, as well as seagrass meadows. An abundance of primary and secondary hardgrounds is reflected in the high number of cementing and byssate species, as well as in the occurrence of species drilling actively into hard substrate. Finally, the dominance of active burrowers suggests a patchwork of habitats, where sandy and muddy soft bottoms occur interspersed. Biostratigraphic analysis constrains the deposits to the early to middle Ottnangian, based on the presence of the index species Flexopecten davidi and the concurrence of several taxa, which have their last or first occurrences within this interval. These are predominantly taxa persisting into the Badenian, therefore allowing for a straightforward differentiation between late Eggenburgian and early Ottnangian assemblages. While a few Central Paratethys endemics reflect a continued semi-isolated position of the area, the majority of the newly arriving species are shared with the Mediterranean and NE Atlantic, documenting the establishment of a faunal migration route via the North Alpine Foreland Basin. In the present study the lectotypes of Nucula mayeri Hörnes, 1865, Saccella subfragilis (Hörnes, 1875) and Lucinoma wolfi (Hoernes, 1875) are designated.

Palynology of the Ordovician Kanosh Shale at Fossil Mountain, Utah

2015 ◽  
Vol 89 (3) ◽  
pp. 424-447 ◽  
Author(s):  
Marco Vecoli ◽  
John H. Beck ◽  
Paul K. Strother
Keyword(s):  
North America ◽  
Shallow Water ◽  
New Taxa ◽  
Middle Ordovician ◽  
Incomplete Knowledge ◽  
Late Cambrian ◽  
Freshwater Influence ◽  
Depositional Setting ◽  
Biological Differences

AbstractPalynomorph assemblages recovered from the Kanosh Shale at Fossil Mountain, Utah, are dominated by operculate acritarchs and cryptospores with minor smaller acritarchs. The present findings add new data to the largely incomplete knowledge of Ordovician acritarch assemblages from Laurentia, up to now known only from very few localities in North America. These populations contain some species in common with acritarchs from the Canning and Georgina basins in Australia and with assemblages from China; they indicate a Middle Ordovician (Dapingian-Darriwilian) age. The assemblage is lacking many typical marine acritarchs of this age, which, in combination with some cryptospores, is probably reflecting the likelihood of freshwater influence in the Kanosh Basin. This observation is congruent with previous interpretations of the depositional setting of the Kanosh Shale as a shallow water lagoon that supported the deposition of carbonate hardgrounds.Four new taxa are described: Busphaeridium vermiculatum n. gen., n. sp.; Digitoglomus minutum n. gen., n. sp.; Turpisphaera heteromorpha n. gen., n. sp.; and Vermimarginata barbata n. gen., n. sp. In addition, the abundance of operculate forms has enabled the revision and a new emendation of the genus Dicommopalla and clarification of the “opalla” complex. We also propose new and revised suprageneric taxa that emphasize inferred biological differences among acritarch genera. The Sphaeromorphitae subgroup is emended to include forms lacking sculptural elements. Two new informal subgroups are proposed: the Superornamenti and the Operculate Acritarchs. Cryptospores are abundant throughout the sections studied and they appear to be more closely related to the late Cambrian Agamachates Taylor and Strother than to Darriwilian and younger Ordovician cryptospores from Gondwana.

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 Remarks on the Messinian evaporites of Zakynthos Island (Io- nian Sea, Eastern Mediterranean).

2016 ◽  
Vol 47 (1) ◽  
pp. 146 ◽  
Author(s):  
V. Karakitsios ◽  
M. Roveri ◽  
S. Lugli ◽  
V. Manzi ◽  
R. Gennari ◽  
...  
Keyword(s):  
Shallow Water ◽  
Eastern Mediterranean ◽  
Thickness Distribution ◽  
Planktonic Foraminifera ◽  
Water Environment ◽  
Foreland Basin ◽  
Seismic Profile ◽  
Depositional Environments ◽  
Borehole Data ◽  
Neogene Sediments

Detailed mapping of the Neogene deposits on Zakynthos Island shows that the Messinian primary evaporite basins, formed over Ionian basement, are delimited by the westernmost outcrop of the Triassic evaporitic diapirs, located west of the Kalamaki-Argasi Messinian gypsum unit. The post-Miocene external Ionian thrust is emplaced west of the Triassic diapirs. Planktonic foraminifera biostratigraphy indicates that primary evaporite accumulation took place probably during the first stage of the Messinian salinity crisis (5.96-5.60 Ma), in shallower parts of a foreland basin, formed over the Pre-Apulian and the Ionian zone basement. Establishment of these depositional environments, before the Ionian thrust emplacement, was probably due to the particularities of the foreland basin, which extended from the external Ionian to the internal Pre-Apulian zone. Field observations, borehole data and an onshore seismic profile show that the Neogene sediments over the Pre-Apulian  basement correspond to the foredeep through forebulge domain of the foreland basin, as it is documented from their spatial thickness distribution. In contrast, the Neogene sediments over the Ionian basement correspond to the wedge top of the foreland basin, which was less subsiding, as it is deduced by their reduced thickness. This lower subsidence rate was the result of the concurrent diapiric movements of the Ionian Triassic evaporites. In Agios Sostis area, located over Pre-Apulian basement, the Neogene sequence is intercalated by decametre-thick resedimented blocks consisting of shallow water selenite. To the southeast, this mass-wasting Messinian gypsum passes to mainly gypsum turbidite. In Kalamaki-Argasi area, located over Ionian basement, the shallow water environment led to the deposition of the observed primary gypsum. Erosion of the primary gypsum of both forebulge and wedge top supplied the foreland basin’s depocenter with gypsum turbidites.

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.

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