Rugose corals from the Upper Ordovician Sholeshook Limestone of southwest Wales with an assessment of the coral affinities and biofacies

2012 ◽  
Vol 48 (6) ◽  
pp. 603-619 ◽  
Author(s):  
C. Baars
Keyword(s):  
Upper Ordovician ◽  
Rugose Corals

Solitary Rugose Corals of the Upper Ordovician Montoya Group, Southern New Mexico and Westernmost Texas

1985 ◽  
Vol 59 (S16) ◽  
pp. 1-58 ◽  
Author(s):  
Robert J. Elias
Keyword(s):  
New Mexico ◽  
North America ◽  
High Energy ◽  
Low Energy ◽  
Red River ◽  
Energy Conditions ◽  
Upper Ordovician ◽  
Rugose Corals ◽  
Solitary Coral ◽  
Mountain Province

The Upper Ordovician (middle Edenian to upper Richmondian) Montoya Group of southern New Mexico and westernmost Texas comprises, in ascending order, the Second Value Dolomite, Aleman Formation, and Cutter Dolomite. Solitary rugose corals in the Second Value are Grewingkia robusta (Whiteaves, 1896), Bighornia sp. cf. B. patella (Wilson, 1926), Streptelasma divaricans (Nicholson, 1875), a new species of Neotryplasma, and Salvadorea? spp. A and B. Salvadorea kingae kingae Nelson, 1981, G. franklinensis n. sp., and G. crassa alemanensis n. subsp. occur in the Aleman. Taxa found in the Cutter are S. kingae cutterensis n. subsp., G. sp. cf. G. franklinensis, and B. sp. cf. B. patella.Grewingkia robusta is the most abundant species in the solitary rugosan assemblage that is present within the Second Value. This assemblage apparently inhabited comparatively deep-water environments. Most of the corals lived in relatively high-energy conditions, but epizoic forms favored low-energy niches. Salvadorea kingae is the most common taxon in the assemblage that characterizes the Aleman-Cutter. This is probably a comparatively shallow-water assemblage. The dominant taxon inhabited relatively low-energy environments, while less common species lived in higher energy conditions. If the distribution of solitary rugose corals in the area of Montoya deposition was related primarily to water depth, a paleobathymetric gradient from relatively deep in the west to predominantly shallow in the southeast existed through Second Value–Aleman time. During Cutter time, water was relatively deep in the southwest and northeast, and predominantly shallow in the southeast. If the degree of environmental restriction was the principal factor limiting the distribution of Montoya solitary Rugosa, open normal marine environments were predominant in the southeast and uncommon in the north and west.Montoya representatives of Grewingkia, Bighornia, and Salvadorea indicate that the area of deposition was situated within the Red River–Stony Mountain Solitary Coral Province, which occupied most of North America during Late Ordovician time. All species of these genera are typical “epicontinental” forms. Neotryplasma, the only “continental margin” taxon, reflects a cratonic margin paleoposition. The discovery of Streptelasma divaricans within Edenian-Maysvillian strata in the Montoya is consistent with an hypothesis that solitary Rugosa were introduced to the Richmond Solitary Coral Province of eastern North America during an early Richmondian transgression.Within the Red River–Stony Mountain Province, geographic speciation and dispersion seem to have been important factors in the evolution and diversification of Grewingkia robusta and related taxa, including G. haysii selkirkensis n. subsp. from the Selkirk Member of the Red River Formation in southern Manitoba. In Salvadorea, speciation events within the New Mexico–Texas area and Williston Basin were apparently rapid, and coincided with onsets of clastic deposition. Evolutionary change within this genus has not been recognized in the Hudson Bay Basin, where there were no clastic influxes.In the Aleman-Cutter sequence of the Montoya Group, recognition of specific intervals bearing solitary rugose corals may permit detailed biostratigraphic, and possibly chronostratigraphic, correlation. The change from a Grewingkia-dominated assemblage to a Salvadorea-dominated assemblage was not synchronous throughout the Red River–Stony Mountain Province, and the ranges of widely distributed species such as G. robusta and S. kingae cannot be considered isochronous from basin to basin. Within particular basins, endemic taxa having restricted stratigraphic ranges, such as G. crassa alemanensis, can be useful biostratigraphic markers. Streptelasma divaricans remains useful as a Richmondian index fossil in strata within the area occupied by the Richmond Province.

Borings in solitary rugose corals of the Selkirk Member, Red River Formation (late Middle or Upper Ordovician), southern Manitoba

1980 ◽  
Vol 17 (2) ◽  
pp. 272-277 ◽  
Author(s):  
Robert J. Elias
Keyword(s):  
Relative Abundance ◽  
Red River ◽  
Marine Environments ◽  
Upper Ordovician ◽  
Shallow Marine ◽  
Rugose Corals

Borings occur in solitary rugose corals from the Selkirk Member of the late Middle or Upper Ordovician Red River Formation in southern Manitoba. They are assigned to Dictyoporus garsonensis n. ichnosp., which was produced by algae, and Trypanites weisei Mägdefrau 1932, made by spionid polychaete annelids. Most, and possibly all, boring occurred while the host corals were alive and in life position. The location and relative abundance of borings support interpretations that unattached curved solitary corals lay with the convex cardinal side in the sediment and the concave counter side facing upward during life, whereas straight conical forms were oriented upright in the sediment. These ichnospecies suggest that host corals lived in very shallow marine environments.

Paleoecology and biostratinomy of solitary rugose corals in the Stony Mountain Formation (Upper Ordovician), Stony Mountain, Manitoba

1982 ◽  
Vol 19 (8) ◽  
pp. 1582-1598 ◽  
Author(s):  
Robert J. Elias
Keyword(s):  
Relative Frequency ◽  
Substrate Surface ◽  
Outer Wall ◽  
Post Mortem ◽  
Upper Ordovician ◽  
Growth Axis ◽  
Coral Size ◽  
Rugose Corals ◽  
External Form

The four species of solitary Rugosa known from the Stony Mountain Formation at Stony Mountain in southern Manitoba belong to different genera, and differ from one another in external form. The distribution and abundance of taxa and their frequency with respect to one another were related to the degree of environmental restriction. The boundary between the Gunn Member and overlying Penitentiary Member corresponds to a marked increase in overall abundance and change in relative frequency. Helicelasma and Bighornia are dominant in the Gunn and lower Penitentiary, respectively. Deiracorallium and Lobocorallium decrease in frequency at the boundary.Larvae of these solitary Rugosa attached to the substrate with their cardinal side. Coralla of Helicelasma, Deiracorallium, and Lobocorallium were oriented in the sediment with the top of the convex cardinal side at or near the substrate surface and the upper part of the concave counter side exposed above it during life. Bighornia lay with the convex counter side in the sediment and the concave cardinal side at least partly exposed. Epizoic bryozoans generally became associated with live hosts, and were especially common on the exposed side of relatively large individuals. Microscopic boring algae infested the outer wall of most corals in the Gunn Member, usually while the hosts were alive. Responses of the polyp to stress and injury are indicated by redirection of the growth axis, constriction of the calice rim, and repair of broken calice rims. The attitudinal and directional orientations of solitary corals suggest that most and possibly all were transported after death. Differences in depositional orientation among the taxa are related to coral form. Currents were unidirectional from the present southeast during Gunn time, and either unidirectional from the southeast or northwest, or oscillating from both directions in early Penitentiary time. Abrasion of coral exteriors was primarily a post-mortem event associated with transportation. Trypanites borings were probably produced by one species of annelid after deposition of the corals. The degree of abrasion and frequency of annelid borings tended to increase with coral size and the duration of exposure before burial.

Late Ordovician solitary rugose corals of the St. Lawrence Lowland, Québec

1990 ◽  
Vol 64 (3) ◽  
pp. 340-352 ◽  
Author(s):  
Robert J. Elias ◽  
Danita S. Brandt ◽  
T. H. Clark
Keyword(s):  
Sedimentation Rate ◽  
Source Area ◽  
High Energy ◽  
Late Ordovician ◽  
Energy Conditions ◽  
Upper Ordovician ◽  
Delta Front ◽  
The North ◽  
Rugose Corals ◽  
Lowland Area

Two species of solitary rugose corals occur in Late Ordovician strata of the St. Lawrence Lowland. Grewingkia canadensis (Billings, 1862) appears in the upper part of the Nicolet River Formation (upper St. Hilaire Member) and is far more common in the overlying Pontgravé River Formation. A single specimen of Streptelasma divaricans (Nicholson, 1875) is known from the Pontgravé River. Their presence confirms that this area is situated within the Richmond Province and that the upper Nicolet River, as well as the Pontgravé River, is Richmondian in age. Solitary Rugosa were introduced to this biogeographic province during an early Richmondian transgression, marked in the upper Nicolet River Formation by a coarser clastic interval. That event permits correlation between the St. Lawrence Lowland in the eastern part of the Richmond Province and the North American type Upper Ordovician (Cincinnatian Series) of the Cincinnati Arch region in the western part of the province.A comparative morphologic, paleoecologic, and biostratinomic analysis of solitary corals indicates that normal, low-energy conditions were interrupted occasionally by high-energy events (probably storms) during deposition of the upper Nicolet River and Pontgravé River Formations. Water depth increased northwestward in the St. Lawrence Lowland area. Deposition of these siliciclastic prodelta to delta front sediments was generally continuous and the sedimentation rate was usually high because of rapid basin subsidence and comparatively close proximity to the Taconic Mountains. In the western part of the Richmond Province, farther from the source area, carbonate as well as clastic sediments accumulated, periods of nondeposition were more frequent, and the sedimentation rate was relatively low. Corals disappeared from the St. Lawrence Lowland area during the Richmondian, when delta top facies of the Bécancour River Formation succeeded the Pontgravé River Formation due to a glacio-eustatic regression and progradation of the Queenston Delta.

Directional orientations of solitary rugose corals

1987 ◽  
Vol 24 (4) ◽  
pp. 806-812 ◽  
Author(s):  
Robert J. Elias ◽  
Robert J. McAuley ◽  
Blair W. Mattison
Keyword(s):  
Flow Direction ◽  
Significant Degree ◽  
Upper Ordovician ◽  
Water Motion ◽  
Lower Silurian ◽  
Rugose Corals ◽  
Flow Directions ◽  
Directional Distributions ◽  
Geologic Record

Unattached solitary rugose corals lying parallel to bedding are common in many Ordovician and younger Paleozoic units, but their directional orientations have seldom been examined. Interpretations based on occurrences in North American Upper Ordovician and Lower Silurian strata provide a foundation for such studies. Distinct directional patterns resulted from preferred orientation with respect to water motion. They indicate transportation rather than biologic orientation, if it can be shown that the corals were not preserved in life position or were abraded to a significant degree before burial. Transported, slightly curved specimens having trochoid to ceratoid form were aligned parallel to currents, with the apex pointing upstream, and (or) were rolled nearly perpendicular to currents or almost parallel to crests of advancing waves, with the apex facing either way but directed slightly upstream. Therefore, unimodal orientation patterns, bimodal patterns with equal peaks that are opposite one another but slightly skewed, and trimodal patterns that are a combination of these can be used to determine flow directions. An apparently bimodal pattern with nearly equal and directly opposite peaks has been observed in a case involving mostly subcalceoloid corals. These individuals may have been aligned parallel to currents or to the direction of wave progression, with the apex facing either way. Random directional distributions do not necessarily indicate low-energy environments. They could have resulted from changes in flow direction during the time in which the sampled stratigraphic interval was deposited or from the effects of bioturbation on corals that were initially preferentially oriented.Directional patterns of solitary rugose corals are of value in paleoecology (recognition of transported assemblages) and basin analysis (determination of paleocurrent directions). They may also prove to be useful in making paleoenvironmental reconstructions (type of water motion, nature of substrate) if the reasons for different types of orientation patterns can be established with experimental work and additional data from the geologic record.

The relationship of the scleractinian corals to the rugose corals

Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver
Keyword(s):  
Critical Points ◽  
Scleractinian Corals ◽  
Convincing Evidence ◽  
Early Triassic ◽  
Rugose Corals ◽  
History Of ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Biologic Factors

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.

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