In situ lingulids from deep-water carbonates of the Middle Ordovician Table Head Group of Newfoundland and the Trenton Group of Quebec

1984 ◽  
Vol 21 (2) ◽  
pp. 194-199 ◽  
Author(s):  
R. K. Pickerill ◽  
T. L. Harland ◽  
D. Fillion
Keyword(s):  
Deep Water ◽  
Fossil Record ◽  
Environmental Indicators ◽  
Outer Shelf ◽  
Head Group ◽  
Middle Ordovician ◽  
Trenton Group ◽  
Water Depths ◽  
Upper Slope

Specimens of in situ lingulids have been discovered in carbonates of the Middle Ordovician Table Head Group of northwestern Newfoundland and Trenton Group of the St. Lawrence Lowland of Quebec. The discoveries have two important implications regarding Palaeozoic lingulid ecology. First, they represent one of the few recordings of in situ lingulids in carbonate substrates of Palaeozoic age and, second, they occur mainly in outer shelf and upper slope sediments (Grondines Member of Neuville Formation, Trenton Group, and Table Cove Formation, Table Head Group), deposited in presumed considerable water depths. Caution must be observed with the use in the fossil record of lingulids as palaeo-environmental indicators.

Coral microatolls and a probable Middle Ordovician example

1990 ◽  
Vol 64 (1) ◽  
pp. 39-43 ◽  
Author(s):  
David R. Kobluk ◽  
Iqbal Noor
Keyword(s):  
Coral Reefs ◽  
Fossil Record ◽  
Scleractinian Coral ◽  
Regional Scale ◽  
Southern Ontario ◽  
Middle Ordovician ◽  
Reef Environments ◽  
Maximum Water ◽  
Water Depths ◽  
Tabulate Corals

A disk-shaped massive colony of Tetradium, from the Middle Ordovician Bobcaygeon Formation in southern Ontario, displays features of a coral microatoll. This is the first pre-Holocene coral microatoll yet described, indicating that some tabulate corals in level-bottom communities were growing as microatolls as do many modern colonial skeleton-secreting organisms.The microatoll therefore is not strictly a Quaternary or even Cenozoic phenomenon, but has a fossil record that may span most of the Phanerozoic. This indicates that the special conditions necessary for microatoll growth have existed outside of reef environments, and were present before the advent of scleractinian coral reefs. It may be possible to use ancient microatolls to estimate absolute water depths at low tide, thereby providing a means for estimating maximum water depths on a local and regional scale.

scholarly journals Taphonomy and ecology of deep-water Ediacaran organisms from northwestern Canada

1992 ◽  
Vol 6 ◽  
pp. 219-219 ◽  
Author(s):  
Guy M. Narbonne ◽  
Robert W. Dalrymple
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Microbial Mats ◽  
Bedding Plane ◽  
Thin Layers ◽  
Sea Bottom ◽  
Windermere Supergroup ◽  
Storm Wave ◽  
Upper Slope

Although most occurrences of Ediacaran fossils are from shallow-shelf deposits, taxonomically-similar assemblages have recently been described from a 2.5 km-thick succession of dark mudstones and turbiditic sandstones in the Windermere Supergroup of the Mackenzie Mountains, northwestern Canada. The paleogeographic position (20-40 km seaward of the shelf edge), abundant evidence of mass flow, and the complete absence of in situ shallow-water features imply that deposition took place on a slope considerably below storm wave-base. Ediacaran fossils were not observed in axial trough deposits (lower parts of the Twitya and Sheepbed formations), but megafossils occur sporadically in lower to middle slope deposits higher in the same formations. Megafossils and trace fossils are present in upper slope settings (Blueflower Formation) at the top of the Ediacaran succession. The megafossil assemblage varies stratigraphically, but in all formations is dominated by discoid forms (e.g. Cyclomedusa, Ediacaria, Nimbia); frondose forms and vendomiids are very rare.Megafossils are preserved mainly as positive features on the soles of thin turbidite beds. Most fossiliferous beds begin with the rippled layer of the turbidite (Tc), but a few begin with the graded (Ta) or parallel-laminated (Tb) layer. Consistent orientation and high relief of individuals, evidence of mutual deformation during growth of adjacent organisms, and other taphonomic features imply that virtually all of the taxa represent benthic polypoid and frond-like organisms (not jellyfish). Slump structures occur commonly in the sandstone fill of fossils, suggesting that many of the organisms were buried alive by the turbidite and later decomposed. Other individuals, even on the same bedding plane, exhibit graded to laminated fill identical to that of the overlying turbidite bed, indicating that the depressions on the sea bottom produced by these individuals were empty at the time of turbidite deposition. Escape structures are absent, suggesting that the Ediacaran organisms were not capable of burrowing up through even thin layers of sand.Ediacaran megafossils are invariably preserved on black, wrinkled surfaces similar to those elsewhere interpreted as microbial mats. Molding of delicate features (including tentacles), preservation of open molds as negative epireliefs, and sedimentological evidence of considerable cohesion of these surfaces relative to the underlying turbiditic muds (Td,e) supports this interpretation, and suggests that microbial mats were as important in the preservation of these deep-water Ediacara faunas as they were in their shallow-water equivalents. The presence of the wrinkled mats and their associated Ediacaran fossils almost exclusively in the pyritic intervals of the succession suggests that both may have lived under exaerobic conditions in this deep-water setting.

The proposed Cambrian–Ordovician global Boundary stratotype and point (GSSP) in Western Newfoundland, Canada

1988 ◽  
Vol 125 (4) ◽  
pp. 381-414 ◽  
Author(s):  
C. R. Barnes
Keyword(s):  
New Species ◽  
Shallow Water ◽  
Head Group ◽  
Middle Cambrian ◽  
Middle Ordovician ◽  
Green Point ◽  
Group A ◽  
Conodont Fauna ◽  
Three New Species

AbstractSections exposing the Cambrian–Ordovician Boundary interval at Broom Point in western Newfoundland have been proposed earlier for a global systemic boundary stratotype. These lie within the Cow Head Group, a late Middle Cambrian to early Middle Ordovician allochthonous unit of limestone, shale, and conglomerate deposited at the toe of the ancient continental slope and on the adjacent continental rise. Several recent studies have further investigated the stratigraphy, sedimentology, and palaeontology of the Cow Head Group and others are under way on magnetostratigraphy and chemostratigraphy. These aspects are reviewed for six key boundary sections representing proximal to distal facies: Cow Head Ledge, Broom Point South, Broom Point North, St Pauls Inlet Quarry, Martin Point, and Green Point. In particular, new data are presented from 260 conodont samples that yielded 15500 conodonts. This intense sampling has allowed the discrimination of minor hiatuses in the proximal to intermediate facies where conglomerates have eroded and cannibalized underlying strata. New conodont data from Broom Point North have lowered the base of the C. lindstromi Zone into unit 74 conglomerates, thereby making this section unsuitable as a boundary stratotype. New collections from Green Point have yielded abundant conodonts and over 9400 conodonts have been recovered from 77 samples.The conodont, graptolite, and trilobite biostratigraphy through the boundary interval is documented allowing accurate correlation between sections and more precisely revealing small hiatuses in the proximal and intermediate facies. The sequence of conodont zones is: Eoconodontus notchpeakensis, Cordylodus proavus, C. caboti, C. intermedius, C. lindstromi and C. angulatus. These can be correlated with trilobite zones established from both in situ and clast faunas from the proximal to intermediate facies and with graptolite assemblages (of Cooper 1979) especially in the intermediate to distal facies. Three new species of Cordylodus are described (C. andresi, C. hastatus and C. tortus) and the full apparatus of Iapetognathus preaengensis is illustrated.The criteria for selecting a global boundary stratotype and point (GSSP) are reviewed in terms of the Cow Head sections. The Green Point section is shown to meet, and largely surpass, the prerequisites required of a stratotype. The Green Point section is proposed to be the global boundary stratotype with the base of the Ordovician System defined at the base of unit 23, which is the base of the Broom Point Member, Green Point Formation, at a level coincident with the base of the Cordylodus lindstromi Zone. In addition to an abundant and superbly preserved conodont fauna, this section preserves the best sequence of earliest planktic graptolites through a 40 m interval; the first nematophorous graptolites (of Assemblage 1) occur in unit 25, 6.9 m above the base of the C. lindstromi Zone. This level can be readily correlated into the proximal facies where both deep and shallow water trilobites (in situ and in clasts, respectively) show the base of the C. lindstromi Zone to lie within the Symphysurina brevispicata trilobite Subzone.

scholarly journals Decapod Crustacea of the Central Paratethyan Ottnangian Stage (middle Burdigalian): implications for systematics and biogeography

2015 ◽  
Vol 66 (3) ◽  
pp. 217-233 ◽  
Author(s):  
Matúš Hyžný ◽  
Mathias Harzhauser ◽  
Wolfgang Danninger
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Fossil Record ◽  
Outer Shelf ◽  
Decapod Crustaceans ◽  
Lower Miocene ◽  
Western Tethys ◽  
Decapod Crustacea ◽  
Portunid Crab ◽  
First Time

AbstractDecapod crustaceans from the Ottnangian (middle Burdigalian, Lower Miocene) of the Western and Central Paratethys remain poorly known. In this study, we review and re-describe mud shrimps (Jaxea kuemeli), ghost shrimps (Gourretiasp.,Calliax michelottii) and brachyuran crabs of the families Leucosiidae, Polybiidae and Portunidae. A dorsal carapace of the genusCalliaxis reported for the first time in the fossil record. Re-examination of the type material ofRandallia strouhali(Leucosiidae) andGeryon ottnangensis(Geryonidae) resulted in a transfer of these species intoPalaeomyra(Leucosiidae) andLiocarcinus(Polybiidae), respectively.Achelous vindobonensis, originally described as a chela of a portunid crab, probably belongs to a member of Polybiidae and is provisionally treated asLiocarcinussp. Only two species,J. kuemeliandC. michelottii, are also known from the Karpatian, the succeeding Paratethyan stage. In most cases, the decapod assemblages of the Ottnangian consist of rather shallow-water taxa whereas the assemblages of the Karpatian consist of deep-water taxa from the middle and outer shelf. The Central Paratethyan assemblages show similarities in genus composition to the Proto-Mediterranean and recent Indo-Pacific regions.Gourretiasp. represents the earliest occurrence of the respective genus in the fossil record. The Oligocene–Early Miocene appearance ofPalaeomyraandLiocarcinusin the circum-Mediterranean implies that sources of present-day diversity hotspots in the Indo-Pacific trace to the Western Tethys (as for other decapod genera), although coeval decapod assemblages in the Indo-Pacific remain poorly known.

Late Ordovician (Katian) brachiopods from the Southern Uplands of Scotland: biogeographic patterns on the edge of Laurentia

2009 ◽  
Vol 100 (3) ◽  
pp. 253-274 ◽  
Author(s):  
Yves Candela ◽  
David A. T. Harper
Keyword(s):  
Northern Ireland ◽  
Deep Water ◽  
Late Ordovician ◽  
Outer Shelf ◽  
Biogeographic Patterns ◽  
Laurentian Margin ◽  
Upper Slope

ABSTRACTSome 40 brachiopod species are known from the localities of Kilbucho and Wallace’s Cast in the Kirkcolm Formation in the Northern Belt of the Southern Uplands of Scotland. The fauna is diverse despite the relatively small numbers of brachiopod specimens (c. 180) available for study. Much of the fauna was transported downslope and is locally preserved in obtrution deposits. It represents a broad census of outer shelf and upper slope palaeocommunities around this part of the Laurentian margin during the early Katian, and is dominated by relatively small plectambonitoid brachiopods. When compared with other circum-Iapetus assemblages, the brachiopods from the Southern Uplands compare most closely with those from the Bardahessiagh Formation, Pomeroy, Northern Ireland, rather than with adjacent, well-known faunas from the Girvan district, SW Scotland. These new data suggest that this part of the Southern Uplands was located in closer proximity to Pomeroy than Girvan, and located in deep-water environments similar to those in the upper parts of the Bardahessiagh Formation.

Allochthonous slope sequence at Lobster Cove Head: evidence for a complex Middle Ordovician platform margin in western Newfoundland

1987 ◽  
Vol 24 (6) ◽  
pp. 1199-1211 ◽  
Author(s):  
Noel P. James ◽  
Jack W. Botsford ◽  
S. Henry Williams
Keyword(s):  
Deep Water ◽  
Carbonate Platform ◽  
Head Group ◽  
Middle Ordovician ◽  
The North ◽  
Platform Margin ◽  
Taconic Orogeny ◽  
Group Contact ◽  
Carbonate Platform Margin ◽  
Shallow Bay

The upper part of an intact sequence of Lower to Middle Ordovician deep-water sediments, which now form a large, disrupted raft within the Rocky Harbour Mélange at Lobster Cove Head, is interpreted as having been deposited downslope from a drowned carbonate platform margin. The entire 50 m thick section is Arenig (late Canadian or Ibexian to early Whiterock) in age; graptolite biostratigraphy demonstrates a correlation with upper parts of the Cow Head Group to the north. The basal part of the section is a proximal facies of the Cow Head Group (Shallow Bay Formation, Factory Cove Member, Beds 9, 10, and part of Bed 11). The upper part of the section consists of interbedded dolostone and shale and is unlike any other sequence in the Cow Head Group. This upper sedimentary sequence is defined as the Lobster Cove Head Member of the Shallow Bay Formation, Cow Head Group. Contact between the two sedimentary packages is also marked by a faunal break and coincides with emplacement of megaconglomerate Bed 12 at Cow Head.This break marks the change from a uniform to complex carbonate platform margin configuration and is here interpreted as the result of synsedimentary faulting. The margin upslope from Cow Head remained in shallow water during the final stages of Cow Head Group deposition, whereas that upslope from Lobster Cove Head was drowned and shed little sediment into deep water. The synsedimentary faulting, which led to rapid subsidence and platform-margin drowning upslope from Lobster Cove Head and possibly the deposition of megaconglomerate Bed 12 at Cow Head, coincides with the onset of the Taconic Orogeny in western Newfoundland.

scholarly journals Environmental patterns in the origin and diversification of deep-water scleractinian and rugose corals

1992 ◽  
Vol 6 ◽  
pp. 89-89
Author(s):  
Mary L. Droser ◽  
Gretchen Hampt ◽  
Steven Clements
Keyword(s):  
Deep Water ◽  
High Energy ◽  
Outer Shelf ◽  
Deep Basin ◽  
Inner Shelf ◽  
Environmental Distribution ◽  
Middle Ordovician ◽  
Modern Distribution ◽  
Rugose Corals ◽  
Initial Appearance

Scleractinian and rugose corals demonstrate a broad environmental distribution and have been documented in strata reflecting deposition from high-energy, nearshore reefal to low-energy basinal settings. Both clades have a relatively high diversity of representatives which live(d) at great depths. While deep-water scleractinian coral banks are well-documented, commonly the deep-water representatives of both clades are the small, solitary, and often delicate forms. In order to determine the nature of diversification of these deep-water forms the paleoenvironments of the earliest Rugosa and representatives of extant deep-water scleractinian families were determined. Environmental patterns of the subsequentdiversification of the Rugosa and scleractinian sub-order Caryophylliina were also documented. Environmental information was determined from independent sedimentological data.The earliest reported Rugosa is Lambeophyllum from the Chazyan Crown Point Limestone (VT, U.S.A.), which was deposited in an nearshore/inner shelf setting. Subsequentto this occurrence, rugosans appear nearly simultaneously in North America, Australia, Europe and China. However, common Lambeophyllum, within the Blackriverian Orwell Limestone (NY, U.S.A), appearsto be the earliest of these occurrences. The Orwell is, likewise interpreted to be shallow water in origin. After their initial appearance in an onshore environment, the Rugosa rapidly expand offshore. While Middle Ordovician Rugosaare of low diversity (1 genus at a given locality), by the end of the Blackriverian they are found in middle and outer shelf settings.Nearly all representatives of families of extant scleractinians now living in deep-water (>200’) also first occur in an onshore environment - primarily the inner shelf. The caryophylliids, the most speciousdeep-water coral clade, first appear in Toarcian age inner shelf strata and soon after occur in outer shelf deposits. However, occurrences of high diversities of caryophylliids (generic diversity greater than 4 at a given locality) are confined to inner shelf settings until the Cretaceous when generic diversities of 2 or more are common in the outer shelf. In the Tertiary, high diversities of caryophylliids are generally restricted to slope and deep basin settings, a pattern which characterises their modern distribution.Both rugose and scleractinian corals expand offshore at low diversities within 5 million years of their first appearance and thus, demonstrate environmental diversification before taxonomic diversification.

Diachronous tectonic collapse of the Ordovician continental margin, eastern Canada: comparison between the Quebec Reentrant and St. Lawrence Promontory

1994 ◽  
Vol 31 (8) ◽  
pp. 1309-1319 ◽  
Author(s):  
Denis Lavoie
Keyword(s):  
Continental Margin ◽  
Foreland Basin ◽  
Head Group ◽  
Upper Ordovician ◽  
Eastern Canada ◽  
Middle Ordovician ◽  
Carbonate Sedimentation ◽  
Shallow Subtidal ◽  
Thickness Variations ◽  
Trenton Group

The Upper Ordovician Trenton Group of southern Quebec represents the last Taconian foreland basin carbonate unit in the Quebec Reentrant, prior to final collapse of Laurentia's continental margin and its burial under synorogenic flysch. The Trenton Group, either conformably or unconformably, overlies the Black River Group and is in turn conformably overlain by the Utica Shales. The tripartite Trenton carbonate unit records progressive deepening: (1) very shallow to shallow subtidal, (2) shallow to deep carbonate ramp, and (3) shallow to deep outer shelf. Regional facies distribution, lithotectonic elements, and thickness variations indicate that the Trenton shelf was dissected by extensional faults delineating blocks subsiding at various rates. This scenario compares favourably with Taconian foreland basin development in the Middle Ordovician Table Head Group at the St. Lawrence Promontory, Newfoundland. A similar stratigraphic succession and tectono-sedimentary history occurring 10–15 Ma earlier at the St. Lawrence Promontory than in the Quebec Reentrant argues for a primary tectonic control for the demise of carbonate sedimentation at the margin. The diachroneity in the foreland evolution can be related to the irregular morphology of the Laurentia continental margin.

Echinoidea of Oregon

1967 ◽  
Vol 24 (6) ◽  
pp. 1385-1401 ◽  
Author(s):  
James E. McCauley ◽  
Andrew G. Carey Jr.
Keyword(s):  
Continental Shelf ◽  
Deep Water ◽  
Strongylocentrotus Purpuratus ◽  
Outer Shelf ◽  
Shallow Waters ◽  
Outer Continental Shelf ◽  
Geographic Ranges ◽  
Dendraster Excentricus ◽  
Upper Slope

Ten species of echinoids are known to occur off Oregon. Three distinct bathymetric groups are recognized: Strongylocentrotus purpuratus, S. franciscanus, and Dendraster excentricus occur in shallow waters from intertidal down to about 65 m; S. echinoides occurs on the outer continental shelf, and Brisaster latifrons and Allocentrotus fragilis occur on the outer shelf and upper slope at depths of about 70–840 m; and Aëropsis fulva, Sperosoma giganteum, Urechinus loveni, and Ceratophysa rosea are found in deep water from depths of 2090 to 3000 m. Bathymetric ranges are extended for six species and geographic ranges are extended for five species.

Brachiopod biostratigraphy of the middle Ordovician Cow Head and Table Head groups, western Newfoundland

1987 ◽  
Vol 24 (1) ◽  
pp. 70-95 ◽  
Author(s):  
Reuben J. Ross Jr ◽  
Noel P. James
Keyword(s):  
Shallow Water ◽  
Water Table ◽  
Deep Water ◽  
Head Group ◽  
Middle Ordovician ◽  
Head Groups

Brachiopods from shallow-water limestone boulders in beds 12, 13, and 14 of the allochthonous Cow Head Group belong in the earliest Whiterockian Orthidiella Zone. Brachiopods of the autochthonous intertidal to deep-water Table Head Group are equivalent to those of the younger Whiterockian Anomalorthis Zone. The Cow Head is older than the Table Head.Integration of the brachiopod data from western Newfoundland with those from the type Whiterockian in Nevada, combined with the evidence of graptolites from both areas, indicates that the Orthidiella Zone spans the Australian Castlemainian, Yapeenian, and lower Darriwilian Dal zones.

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