Depositional Environments and Conodont-Based Correlation of the Long Point Formation (Middle Ordovician), Western Newfoundland

The depositional history of the neoautochthonous mid-Caradocian Long Point Formation, which overlies the lower clastic slices of the Humber Arm Klippe, is characterized by two major periods of sedimentation. Out of a total thickness of some 600 m, slightly less than 60 m make up a lower sequence of limestone, minor shales, and a basal sandstone unit, which appears to have been deposited in an environment (or series of environments) characterized by beachsands, mudflats, lagoons, (?) carbonate bank, and a fringing reef. The remainder of the Long Point deposits exhibit several criteria that are suggestive of the general environment of a prograding fluviomarine delta. It appears possible that uppermost Long Point strata are fluviatile in origin.In terms of graptolite and conodont zonations, the Long Point Formation belongs within the Diplograptus multidens and Amorphognathus tvaerensis Zones, respectively. The base of the Long Point Formation probably coincides with the base of the Climacograptus peltifer Zone of the British standard graptolite zonation and with that of the Prioniodus gerdae conodont subzone.

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Graptolite Biostratigraphy and Depositional History of Middle Ordovician Shales, Southern Appalachians: ABSTRACT

AAPG Bulletin ◽

10.1306/94885c41-1704-11d7-8645000102c1865d ◽

1986 ◽

Vol 70 ◽

Author(s):

Stanley C. Finney

Keyword(s):

Southern Appalachians ◽

Depositional History ◽

Middle Ordovician ◽

History Of

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Radiogenic isotope chemostratigraphy reveals marine and nonmarine depositional environments in the late Mesoproterozoic Borden Basin, Arctic Canada

Geological Society of America Bulletin ◽

10.1130/b35060.1 ◽

2019 ◽

Vol 131 (11-12) ◽

pp. 1965-1978 ◽

Cited By ~ 4

Author(s):

Timothy M. Gibson ◽

Sarah Wörndle ◽

Peter W. Crockford ◽

T. Hao Bui ◽

Robert A. Creaser ◽

...

Keyword(s):

Chemical Weathering ◽

Depositional Environments ◽

Eukaryotic Evolution ◽

Arctic Canada ◽

Seawater Chemistry ◽

Depositional History ◽

Radiogenic Isotope ◽

Red Algal ◽

History Of ◽

Global Increase

Abstract The ca. 1050 Ma Bylot Supergroup in Arctic Canada is one of the best-preserved archives of late Mesoproterozoic geochemistry and biology and offers evidence that this period of Earth history may have been more biogeochemically dynamic than previously appreciated. The Bylot Supergroup was deposited in the Borden Basin and is the most thoroughly studied stratigraphic succession from a series of broadly contemporaneous late Mesoproterozoic intracratonic basins known as the Bylot basins. This ∼6-km-thick mixed carbonate-siliciclastic succession has undergone minimal postdepositional deformation and is now exposed on Baffin and Bylot Islands, Nunavut, Canada. Deep-water and tidally influenced carbonate facies, traditionally interpreted as marine, have yielded important insights into the evolution of Proterozoic seawater chemistry; however, more recent studies indicate that the Borden Basin was restricted marine or lacustrine for portions of its depositional history. Here, we present new multiproxy radiogenic isotope chemostratigraphic data spanning the Bylot Supergroup. A comparison of stratigraphic trends in radiogenic isotope data from hydrogenous (black shale 187Os/188Os and limestone 87Sr/86Sr) and detrital (whole-rock mudstone 143Nd/144Nd) sedimentary phases elucidates the complex hydrologic history of the Borden Basin and reconciles these disparate interpretations. Episodic coupling and decoupling between the composition of basin waters (from Os and Sr isotopes) and the local weathering input to the basin (from Nd isotopes) indicate that depositional environments within the Borden Basin fluctuated between marine and nonmarine (i.e., lacustrine). Variations in basin hydrology controlled secular sedimentation patterns through changes in basin water chemistry. These interpretations help to characterize the environment in which the early red algal fossil Bangiomorpha pubescens evolved. Episodically restricted epeiric seaways, such as within the Borden Basin, were relatively widespread within Rodinia and may have exerted unique selective pressures on eukaryotic evolution in the Mesoproterozoic Era. Hydrogenous and detrital radiogenic isotope chemostratigraphy, as implemented in this study, may provide a useful paleoenvironmental framework for future paleontological studies aimed at testing the role of freshwater environments in eukaryotic evolution. In addition, 87Sr/86Sr compositions from 81 new middle Bylot Supergroup marine limestone samples, calibrated by recent Re-Os geochronology, contribute to the terminal Mesoproterozoic marine 87Sr/86Sr curve. These data display a rise from ∼0.705 to 0.706 that reflects weathering of the active Grenville orogenic belt and demonstrates a global increase in chemical weathering during the amalgamation of Rodinia.

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Sedimentological Archives in Lake Deposits

Paleolimnology ◽

10.1093/oso/9780195133530.003.0011 ◽

2003 ◽

Author(s):

Andrew S. Cohen

Keyword(s):

Time Scales ◽

Depositional Environments ◽

Sources Of Information ◽

Geological Time ◽

Depositional History ◽

Sedimentary Deposits ◽

Hill Slope ◽

History Of ◽

Biological Attributes ◽

Lake Deposits

Lake sediments are both repositories and sources of information about lake history. Depositional products tell us about the mechanisms of transport or accumulation of important geochemical and fossil archives, but important clues about that history are imbedded in the pattern of sedimentation itself. Geologists have recognized this fact since the earliest paleolimnological studies. Although he would certainly not have called himself a paleolimnologist, Charles Lyell’s (1830) classic studies and interpretation of the depositional environments of the Eocene Paris Basin set the tone for a time-honored approach to the study of ancient lake deposits. Lyell recognized that understanding the physical, chemical, and biological attributes of lakes that affect sedimentation, obtained through modern observation, must be applied to a four-dimensional (spatial plus time) analysis of sedimentary deposits and depositional history. However, not everything we need to know or every process we need to invoke will necessarily arise from our short-term observations of modern lakes. Events that are unlikely to occur in the course of a brief, several-year experiment or period of monitoring may become virtual certainties over the long history of some lakes and may leave a sedimentary archive of which we have little prior understanding from modern studies (Dott, 1983). Furthermore, the sedimentary response that we observe to some external forcing event may differ depending on the time scale over which we observe the response (Dearing, 1991). Consider a hill slope that is undergoing accelerated erosion, and that is producing an accumulation of sediment in a downstream channel as a result of land-clearing activities. Initially there may be no response in terms of sedimentation rate in the downstream lake; all of the sediment is being held in temporary storage. This process may occur over time scales of a few decades. At some later time a triggering event, perhaps a series of abnormally high rainfall and discharge years, causes this sediment to be released to the lake, now at an accelerated rate. This becomes a sedimentary response that the paleolimnologist can record. But, over geological time scales of millennia or longer, the original process may be modified, and new ones may gain in importance.

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Petrology and depositional history of a Middle Ordovician carbonate platform: Chickamauga Group, northeastern Tennessee

Geological Society of America Bulletin ◽

10.1130/0016-7606(1984)95<568:padhoa>2.0.co;2 ◽

1984 ◽

Vol 95 (5) ◽

pp. 568 ◽

Cited By ~ 11

Author(s):

STEPHEN C. RUPPEL ◽

KENNETH R. WALKER

Keyword(s):

Carbonate Platform ◽

Depositional History ◽

Middle Ordovician ◽

History Of

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Conodont biostratigraphy and depositional history of the Darriwilian (Middle Ordovician) Pygodus serra Zone, western Argentina

Andean geology ◽

10.5027/andgeov46n2-3115 ◽

2019 ◽

Vol 46 (2) ◽

pp. 336

Author(s):

Susana Heredia ◽

Ana Mestre ◽

Cintia Kaufmann ◽

Tatiana Soria

Keyword(s):

Variable Amount ◽

Depositional History ◽

Middle Ordovician ◽

Clastic Rocks ◽

Stratigraphic Record ◽

Conodont Zone ◽

History Of ◽

San Rafael ◽

Clastic Sedimentary ◽

Almost All

The stratigraphic record of the Pygodus serra conodont Zone in the Cuyania terrane of western Argentina is discussed in this contribution. Three well-known sections were sampled in Precordillera and the San Rafael Block. The studied successions are composed mainly by clastic rocks with variable amount of carbonate. The lower part of Ponón Trehué Formation of the San Rafael Block and the La Cantera Formation of the Eastern Precordillera are composed of conglomerate and represent the input of coarse clastic deposits to the Cuyania basin. The Los Azules Formation, in Los Amarillitos section of the Central Precordillera, has a massive sandstone bed with carbonate nodules in a section largely of black shale. Key conodonts recovered from these sections indicate a correlation to the E. robustus and E. lindstroemi subzones of the Pygodus serra Zone of the upper Darriwillian Stage (Middle Ordovician Series). The species in the Ponón Trehué Formation are almost all the same as those in the Precordillera sections. Correlation of the clastic sedimentary successions between the three sections indicates that vertical facies changes were not controlled by eustasy. More likely, they were controlled by differential tectonic subsidence.

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The tectonics and depositional history of the Ordovician and Silurian rocks of Notre Dame Bay, Newfoundland

Canadian Journal of Earth Sciences ◽

10.1139/e85-060 ◽

1985 ◽

Vol 22 (4) ◽

pp. 607-618 ◽

Cited By ~ 27

Author(s):

R. J. Arnott ◽

W. S. McKerrow ◽

L. R. M. Cocks

Keyword(s):

Strike Slip ◽

Late Ordovician ◽

Island Arc ◽

The West ◽

Depositional History ◽

Middle Ordovician ◽

The North ◽

Lower Ordovician ◽

History Of ◽

Ophiolitic Rocks

In the Notre Dame Bay region, ophiolitic rocks underlie a thick sequence of Lower Ordovician volcanic-arc rocks to the north of the Lobster Cove – Chanceport Fault. Neither this fault nor the Lukes Arm – Sops Head Fault shows evidence of very large strike-slip movements, as parts of the same arc, together with much arc-derived detritus, straddle both faults. Towards the east, this arc-derived detritus becomes more distal in aspect and passes laterally into the Dunnage Mélange. During the Middle Ordovician Epoch (late Llandeilo and early Caradoc), most areas show a marked decrease in volcanic activity and in the amount of coarse detritus deposited. Coarse turbidites reappear, at different times in different areas, during the Late Ordovician. These are related to several fault-bounded basins and to movements on the Lukes Arm – Sops Head Fault. Many of these faults, particularly in the east, are marked by olistostromes, several of which can be dated by fossils as Late Ordovician and Early Silurian. The whole region, between the Reach Fault on the east and the Baie Verte – Brompton Line on the west, has a stratigraphic unity. If it has been moved by strike slip relative to the Long Range, then any such fault must lie to the west of the Baie Verte – Brompton Line. The interpretation of an Early Ordovician island arc moving above an easterly directed subduction zone is in accord with both the geochemical and palaeontological evidence. The Notre Dame Bay region may have been converted into a transform-dominated margin in the Late Ordovician and Early Silurian in a manner analogous to the oblique slip tectonic regimes of the Californian and New Zealand margins during the Tertiary, with a precursor of the Reach Fault marking the edge of the continent after the Notre Dame island arc had collided with North America.

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Upper Middle Ordovician submarine fans and associated facies, northeast of Quebec City

Canadian Journal of Earth Sciences ◽

10.1139/e81-094 ◽

1981 ◽

Vol 18 (6) ◽

pp. 981-994 ◽

Cited By ~ 6

Author(s):

Edward S. Belt ◽

Louise Bussières

Keyword(s):

Source Region ◽

Depositional Environments ◽

Turbidity Currents ◽

Quebec City ◽

Submarine Fan ◽

Bottom Currents ◽

Middle Ordovician ◽

Submarine Fans ◽

Facies Associations ◽

Carbonate Bank

Autochthonous upper Middle Ordovician strata northwest of Logan's Line and northeast of Quebec City have been subdivided into six facies types. One or more facies type characterizes the revised formations of our previous report (Belt et al.). These facies were deposited in the following depositional environments: moderately shallow carbonate bank; deeper carbonate slope and foot of slope; submarine fan; and basin plain. The submarine fan facies (Beaupré and Saint-Irénée Formations) contain the only facies with appreciable sandstone. The source region of the sandstones (determined by petrography and paleocurrents) lay to the southeast of Logan's Line. This source was uplifted and eroded during the early phases of the Taconic Orogeny. Turbidity currents and debris flows brought sand into a foredeep trough that lay between the mobile Taconic Orogen and the more stable Canadian Shield. During Trenton time, a carbonate bank developed on the margin of the shield, northwest of the trough axis. Olistostromes, produced by bank-edge collapse, slid southeast into the trough and intercalated with the Saint-Irénée sandy fan lobes derived from the other side of the foredeep basin. Bottom currents, reworking the sand, flowed southwest along the axis of the trough. Later, after regional foundering of the carbonate bank, a larger (Beaupré Formation) submarine fan developed in the foredeep basin. Bottom currents continued reworking the sands down the trough to the southwest.The submarine fans found in this region never developed some of the facies associations commonly expected of suprafan lobes. The initial fan facies consists of lenticular coarse and pebbly sandstone and shale that are only rarely organized into coarsening-up successions. No definite feeder channel deposits are found in the Saint-Irénée Formation although three are recognized in the middle Beaupré Formation at the type section. The presence of these channels plus the geometry of all Beaupré facies and the paleocurrent divergence show that these facies are not disorganized base-of-slope or basin-plain deposits, but best fit a submarine fan model.

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