Middle to Late Ordovician rocky bottoms and rocky shores from the Manitoulin Island area, Ontario

1989 ◽  
Vol 26 (4) ◽  
pp. 642-653 ◽  
Author(s):  
Markes E. Johnson ◽  
Rong Jia-yu
Keyword(s):  
North America ◽  
Rocky Shore ◽  
Late Ordovician ◽  
Depositional Environments ◽  
Lake Huron ◽  
Rocky Shores ◽  
Rare Association ◽  
Brachiopod Fauna ◽  
Rocky Bottoms ◽  
Topographic Relief

The Precambrian Lorrain Quartzite is exposed on Manitoulin, Great Cloche, and Birch islands in Lake Huron off the mainland of Ontario. Metamorphism created a massive unit, which later formed a resistant angular unconformity overlain by a succession of strata deposited from Middle to Late Ordovician times. At the start of Ordovician sedimentation, topographic relief was at least 125 m when the quartzite hills formed an archipelago of small, rocky islands. The Ordovician–Precambrian unconformity provides insight on a changing series of depositional environments over rocky bottoms and rocky shores. Four Ordovician units are well represented. The Swift Current Formation includes some red beds, while the younger Cloche Island and Cobourg formations are carbonates. The Collingwood Formation is a black shale. The first three include eroded quartzite clasts typical of a rocky-shore setting. The unconformity marked by the Collingwood Formation indicates a rapid transgression with little time for the accumulation of eroded quartzite clasts. A rich trilobite and orthid brachiopod fauna was recovered from the Collingwood Formation immediately above the Lorrain Quartzite and it represents a rare association that lived in a rocky-bottom setting. This fauna includes the first-reported occurrence of the genus Triarthrus from Manitoulin Island. The Collingwood transgression is equated with a major rise in sea level widely recognized elsewhere in North America and Scandinavia.

Late Ordovician nearshore faunas and depositional environments, northwestern Maine

1994 ◽  
Vol 68 (5) ◽  
pp. 925-937 ◽  
Author(s):  
Stephen G. Pollock ◽  
David A. T. Harper ◽  
David Rohr
Keyword(s):  
Tidal Flat ◽  
Sedimentary Basins ◽  
Late Ordovician ◽  
Depositional Environments ◽  
Swash Zone ◽  
Nearshore Environments ◽  
Lake Formation ◽  
East Lake ◽  
Laurentian Margin ◽  
Brachiopod Fauna

The Little East Lake Formation represents a spectrum of Late Ordovician (Ashgill) nearshore environments. These physical environments are characterized by a variety of quartz- and feldspar-rich sandstone and slate. Depositional environments include neritic nearshore, beach, tidal flat, and alluvial(?). The beach and neritic nearshore environments contain a variety of fossil invertebrates. The majority of the brachiopod fauna is confined to two taxa: Eodinobolus rotundus Harper, 1984, and Dalmanella testudinaria ripae Mitchell, 1978 (in Cocks, 1978). Some of the specimens have been broken and abraded suggesting transport within the beach swash zone. Gastropods include Lophospira cf. L. milleri (Hall), Lophospira(?), Trochonemella cf. T. notabilis (Ulrich and Scofield), and Daidia cerithioides (Salter). Tidal-flat environment contains the trace fossils Palaeophycus and Planolites.The Late Ordovician (Caradoc and Ashgill) sedimentary basins developed subsequent to the collisional Taconian orogeny, wherein an arc accreted to the eastern Laurentian margin. Prior paleomagnetic reconstructions place the southeastern continental margin of Laurentia at approximately 25° south latitude during the Late Ordovician. Using these reconstructions, the siliciclastic Ashgill rocks discussed here would have been deposited in an elongated, northeast-trending basin on the southeastern Laurentian margin. The fauna developed along this margin, but in contrast to possibly adjacent Irish and Scottish assemblages, was located in much shallower water.

Intensity of Human Predation on Rocky Shores at Las Cruces in Central Chile

1987 ◽  
Vol 14 (2) ◽  
pp. 143-149 ◽  
Author(s):  
L. René Durán ◽  
Juan Carlos Castilla ◽  
Doris Oliva
Keyword(s):  
Activity Pattern ◽  
Rocky Shore ◽  
Rocky Shores ◽  
Central Chile ◽  
Temporal Grouping ◽  
Human Predation

The rocky shore of central Chile is heavily harvested by mariscadores de orilla and skin-divers, but their catches are not considered in the fishery statistics. The aim of the present paper is to estimate the intensity of human predation and annual catch of each of the species taken at Las Cruces, Central Chile. The activity pattern of both categories of collectors demonstrate a temporal grouping. The observation of mariscadores de orilla and skin-divers in 3 sectors of fringe totalling 1,500 m of rocky shore during 12 months allowed us to estimate the annual catch per species caught (kg per year).

scholarly journals Discovery of a new species of genus Typhlodromus Scheuten (Acari: Phytoseiidae: Typhlodrominae) on rocky shore habitat from Lanyu Island

2017 ◽  
Vol 22 (10) ◽  
pp. 1639
Author(s):  
Jhih-Rong Liao ◽  
Chyi-Chen Ho ◽  
Chiun-Cheng Ko
Keyword(s):  
New Species ◽  
Rocky Shore ◽  
Biological Control Agent ◽  
Control Agent ◽  
Morphological Description ◽  
Rocky Shores ◽  
Mountain Areas ◽  
Phytoseiid Mites ◽  
First Time ◽  
A New Species

Phytoseiid mites have been intensively surveyed in Taiwan during the past decades because of their potential as biological control agent. Despite the fact, many regions of Taiwan remain under-explored especially in mountain areas and neighboring islands. Typhlodromus (Anthoseius) crossostephium sp. nov. was collected from Crossostephium chinense (L.) Makino (Asteraceae) on rocky shore habitat during a survey on Lanyu Island. In this paper, presence of a phytoseiid mite on rocky shores is reported for the first time. A detailed morphological description of the new species and a key to the Taiwanese species of subgenus Anthoseius are provided.

Paleoenvironmental Reconstruction Based on Horn Corals, with an Example from the Late Ordovician of North America

Palaios ◽  
1988 ◽  
Vol 3 (1) ◽  
pp. 22 ◽  
Author(s):  
Robert J. Elias ◽  
Ronald G. Zeilstra ◽  
Thomas N. Bayer
Keyword(s):  
North America ◽  
Late Ordovician ◽  
Paleoenvironmental Reconstruction

scholarly journals Evolution of the early Mesozoic Cordilleran arc: The detrital zircon record of back-arc basin deposits, Triassic Buckskin Formation, western Arizona and southeastern California, USA

Geosphere ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 1042-1057
Author(s):  
N.R. Riggs ◽  
T.B. Sanchez ◽  
S.J. Reynolds
Keyword(s):  
North America ◽  
Detrital Zircon ◽  
Colorado Plateau ◽  
Depositional Environments ◽  
Coarse Grained ◽  
Land Bridge ◽  
Magmatic Arc ◽  
Early Mesozoic ◽  
Northern Nevada ◽  
Back Arc

Abstract A shift in the depositional systems and tectonic regime along the western margin of Laurentia marked the end of the Paleozoic Era. The record of this transition and the inception and tectonic development of the Permo-Triassic Cordilleran magmatic arc is preserved in plutonic rocks in southwestern North America, in successions in the distal back-arc region on the Colorado Plateau, and in the more proximal back-arc region in the rocks of the Buckskin Formation of southeastern California and west-central Arizona (southwestern North America). The Buckskin Formation is correlated to the Lower–Middle Triassic Moenkopi and Upper Triassic Chinle Formations of the Colorado Plateau based on stratigraphic facies and position and new detrital zircon data. Calcareous, fine- to medium-grained and locally gypsiferous quartzites (quartz siltstone) of the lower and quartzite members of the Buckskin Formation were deposited in a marginal-marine environment between ca. 250 and 245 Ma, based on detrital zircon U-Pb data analysis, matching a detrital-zircon maximum depositional age of 250 Ma from the Holbrook Member of the Moenkopi Formation. An unconformity that separates the quartzite and phyllite members is inferred to be the Tr-3 unconformity that is documented across the Colorado Plateau, and marks a transition in depositional environments. Rocks of the phyllite and upper members were deposited in wholly continental depositional environments beginning at ca. 220 Ma. Lenticular bodies of pebble to cobble (meta) conglomerate and medium- to coarse-grained phyllite (subfeldspathic or quartz wacke) in the phyllite member indicate deposition in fluvial systems, whereas the fine- to medium-grained beds of quartzite (quartz arenite) in the upper member indicate deposition in fluvial and shallow-lacustrine environments. The lower and phyllite members show very strong age and Th/U overlap with grains derived from Cordilleran arc plutons. A normalized-distribution plot of Triassic ages across southwestern North America shows peak magmatism at ca. 260–250 Ma and 230–210 Ma, with relatively less activity at ca. 240 Ma, when a land bridge between the arc and the continent was established. Ages and facies of the Buckskin Formation provide insight into the tectono-magmatic evolution of early Mesozoic southwestern North America. During deposition of the lower and quartzite members, the Cordilleran arc was offshore and likely dominantly marine. Sedimentation patterns were most strongly influenced by the Sonoma orogeny in northern Nevada and Utah (USA). The Tr-3 unconformity corresponds to both a lull in magmatism and the “shoaling” of the arc. The phyllite and upper members were deposited in a sedimentary system that was still influenced by a strong contribution of detritus from headwaters far to the southeast, but more locally by a developing arc that had a far stronger effect on sedimentation than the initial phases of magmatism during deposition of the basal members.

II.—On a New Genus of Favosite Coral from the Niagara Formation (U. Silurian), Manitoulin Island, Lake Huron

1879 ◽  
Vol 6 (6) ◽  
pp. 244-246 ◽  
Author(s):  
G. Jennings Hinde
Keyword(s):  
North America ◽  
Coral Reefs ◽  
New Genus ◽  
Great Majority ◽  
Lake Huron ◽  
Fossil Corals ◽  
The Matrix

Certain zones of the massive grey dolomite belonging to the Niagara Formation in North America are so largely composed of fossil corals as to indicate similar conditions of formation to that of the coral reefs of the present age. Perhaps no better examples of these Palæozoic coral reefs could be found than those which are exposed in many tracts of the surface of the Great Manitoulin Island, which are literally covered with complete and fragmentary corals in a silicified condition, which have been weathered out of the matrix of hard dolomite in which they had been imbedded. The great majority of these corals belong to the well-known genera Favosites, Halysites, Heliolites, Alveolites, Cænites, Syringopora, Strombodes, Cyathophyllum, Zaphrentisand Omphyma, and many of the species are also common to the Silurian rocks of Europe. A recent search in the dèbris of one of these ancient reefs has brought to light a coral which appears to belong to a new genus, with the following characters.

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