Sedimentology of an Early Silurian carbonate ramp: the Manitoulin Formation, southern Ontario

1993 ◽  
Vol 30 (12) ◽  
pp. 2453-2464 ◽  
Author(s):  
A. S. Anastas ◽  
M. Coniglio
Keyword(s):  
Carbonate Ramp ◽  
Michigan Basin ◽  
Storm Events ◽  
Fair Weather ◽  
Continuous Transition ◽  
Southern Ontario ◽  
Sediment Reworking ◽  
Lower Silurian ◽  
Shallow Basin ◽  
Water Facies

The Manitoulin Formation is a pervasively dolomitized Lower Silurian carbonate unit that was deposited in the Michigan Basin and locally in the Appalachian Basin. The formation reaches a maximum thickness of 11.1 m in southern Ontario and can be subdivided into eight facies and four regionally correlatable facies assemblages. Owing to the relatively continuous transition of shallow to deeper water facies from the northern to southern portions of the study area, the Manitoulin Formation is interpreted as having formed on a carbonate ramp with a southerly component of dip. Our study suggests that the Algonquin Arch, which is transected by the outcrop belt, did not significantly influence deposition or separate the Michigan and Appalachian basins.Depending on its location on the ramp, the Manitoulin Formation shows evidence of varying degrees of episodic storm events alternating with fair-weather processes such as wave shoaling, sediment reworking, and bioturbation. Apart from bioturbation, these fair-weather processes became less prevalent to the south. The gently dipping antecedent topography, the temporary lack of frame-builders, and a shallow basin setting led to the creation of a carbonate ramp rather than a rimmed shelf.

Tempestites recorded as variable Pentamerus layers in the Lower Silurian of southern Norway

1989 ◽  
Vol 63 (2) ◽  
pp. 195-205 ◽  
Author(s):  
Markes E. Johnson
Keyword(s):  
Storm Events ◽  
Fair Weather ◽  
Marine Waters ◽  
Lower Silurian ◽  
Sea Bed ◽  
Storm Wave ◽  
Southern Norway ◽  
Average Size ◽  
Tabulate Corals

The brachiopod Pentamerus oblongus is especially abundant in the Lower Silurian Rytteråker Formation, which occurs widely throughout the Oslo region in southern Norway. Alternating thin limestones and shales typically occur in a shallowing-upward sequence ending in a massive grainstone often rich in tabulate corals and stromatoporoids. In the lower beds, colonization by pentamerid populations was enhanched by prior emplacement of an orthotetacean shell pavement over the clastic sea bed. Individual Pentamerus size decreases with increasing disturbance of populations or their fragmentation as lag deposits nearer the stratigraphic level of the massive grainstone. The frequency of specific storm events and the changing depth to the sea bed may be indexed according to the average size of pentamerid shells in a given population and the degree to which the population is disturbed. Preservation of prominent growth lines (assumed to be annual) suggests storms stirred the sea bed in deeper waters on an 8–10 year cycle. In shallower waters, storms more regularly disturbed the sea bed every 2–3 years. These data corroborate the interpretation that the Pentamerus community inhabited marine waters below fair-weather wave base, but still within reach of storm wave base.

Geochemical evidence of tropical cyclone controls on shallow-marine sedimentation (Pliocene, Taiwan)

Geology ◽  
2021 ◽  
Author(s):  
Shahin E. Dashtgard ◽  
Ludvig Löwemark ◽  
Pei-Ling Wang ◽  
Romy A. Setiaji ◽  
Romain Vaucher
Keyword(s):  
Foreland Basin ◽  
Weather Conditions ◽  
Extreme Weather ◽  
Extreme Weather Events ◽  
Fair Weather ◽  
Shallow Marine ◽  
Sediment Reworking ◽  
Virtual Absence ◽  
Marine Strata ◽  
Marine Sedimentation

Shallow-marine sediment typically contains a mix of marine and terrestrial organic material (OM). Most terrestrial OM enters the ocean through rivers, and marine OM is incorporated into the sediment through both suspension settling of marine plankton and sediment reworking by tides and waves under fair-weather conditions. River-derived terrestrial OM is delivered year-round, although sediment and OM delivery from rivers is typically highest during extreme weather events that impact river catchments. In Taiwan, tropical cyclones (TCs) are the dominant extreme weather event, and 75% of all sediment delivered to the surrounding ocean occurs during TCs. Distinguishing between sediment deposited during TCs and that redistributed by tides and waves during fair-weather conditions can be approximated using δ13Corg values and C:N ratios of OM. Lower Pliocene shallow-marine sedimentary strata in the Western Foreland Basin of Taiwan rarely exhibit physical evidence of storm-dominated deposition. Instead they comprise completely bioturbated intervals that transition upward into strata dominated by tidally generated sedimentary structures, indicating extensive sediment reworking under fair-weather conditions. However, these strata contain OM that is effectively 100% terrestrial OM in sediment that accumulated in estimated water depths <35 m. The overwhelming contribution of terrestrially sourced OM is attributed to the dominance of TCs on sedimentation, whereby ~600,000 TCs are estimated to have impacted Taiwan during accumulation of the succession. In contrast, the virtual absence of marine OM indicates that organic contributions from suspension settling of marine OM is negligible regardless of the preserved evidence of extensive reworking under fair-weather conditions. These data suggest that (1) even in the absence of physical expressions of storm deposition, TCs still completely dominate sedimentation in shallow-marine environments, and (2) the organic geochemical signal of preserved shallow-marine strata is not reflective of day-to-day depositional conditions in the environment.

Sedimentary and Paleoclimatic Controls on Caddisfly (Insecta: Trichoptera) Assemblages during the Last Interglacial-to-Glacial Transition in Southern Ontario

1995 ◽  
Vol 43 (1) ◽  
pp. 90-105 ◽  
Author(s):  
Nancy E. Williams ◽  
Nicholas Eyles
Keyword(s):  
Species Richness ◽  
Sedimentary Facies ◽  
Weather Conditions ◽  
Climatic Conditions ◽  
Last Interglacial ◽  
Fair Weather ◽  
Southern Ontario ◽  
Valley Site ◽  
Climatic Cooling ◽  
Temperate River

AbstractSouthern Ontario, Canada, has late Pleistocene deposits that contain evidence for climatic cooling during the last interglacial/glacial transition and much of the succeeding Wisconsin glaciation. Fossils of lacustrine and riverine caddisflies (Insecta: Trichoptera) are abundant and well-preserved in these deposits. We examined 26 samples from the interglacial section exposed in the Don Valley Brickyard and compared their caddisfly assemblages with those recovered from the overlying early Wisconsin Scarborough Formation deposits at nearby Scarborough Bluffs. Fifty-one caddisfly taxa in 16 families were recovered from the Don Valley site. Fossil abundance and species richness appear related to the storm or fair-weather conditions inferred from the sedimentary facies. Caddisfly fossils were most abundant and species richness highest in fair-weather, peaty, rippled sands. Highest proportions of river species as opposed to lake species were recovered from sands (storm and fair-weather). Assemblages from both sites indicate the presence of a large and productive river flowing into ancestral Lake Ontario. However, the river assemblage appeared to be far more sensitive to environmental change than the relatively stable assemblage representing the thermally buffered lake. Warm temperate river species such as Hydropsyche bidens, Hydropsyche mississippiensis, Macrostemum carolina, and Potamyia flava are present in the lower Don samples but absent from the Scarborough Bluffs deposits, while indicators of cooler than present climatic conditions such as Arctopsyche Indogensis and Hagenella canadensis are present in the Scarborough Bluffs sediments but absent from the lower Don samples. For the interval from about 80,000 to 55,000 yr B.P., we infer a climatic cooling from temperature about 2°C warmer than present to about 3°C cooler than present.

How do storm events and fair-weather conditions affect sedimentation patterns on salt marshes?

2020 ◽  
Author(s):  
Davide Tognin ◽  
Mattia Pivato ◽  
Andrea D'Alpaos ◽  
Luca Carniello
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Weather Conditions ◽  
Marsh Surface ◽  
Sediment Traps ◽  
Vertical Accretion ◽  
Storm Events ◽  
Fair Weather ◽  
Short Term ◽  
Intense Storm

<p>Coastal salt marshes are extremely important ecosystems, occupying the transitional zone between submerged and emerged environments. Since salt marshes are based on a delicate balance between hydrodynamics and sedimentary processes, their future is heavily affected by relative sea-level rise (RSLR), caused by both subsidence and eustatism. If vertical accretion is sufficient, salt marshes can keep pace with RSLR; otherwise, lack of sediment input can eventually lead to plant death and marsh drowning, transforming these landforms into tidal flats and subtidal platforms. Resuspension driven by intense meteorological events can represent an important source of sediment for salt marsh accretion in tidal environments characterized by negligible fluvial sediment supply. However, it is not yet clear what is the mutual role and relative contribution of intense storm events and fair-weather conditions in terms of sedimentation patterns. To better understand sedimentation dynamics on salt marshes, we stared a field campaign in October 2018 to measure vertical accretion rate and sediment accumulation.</p><p>In the Venice lagoon (Italy), which is the largest lagoon in the Mediterranean sea and is characterized by a semi-diurnal, microtidal regime, we selected three study areas: the San Felice and Sant’Erasmo salt marshes in the northern lagoon and the Conche salt marsh in the southern lagoon. Subsidence at all these study sites ranges between 1.0 and 2.0 mm yr<sup>-1</sup>, and the rate of sea-level rise is of about 2.0 mm yr<sup>-1</sup>, for a total rate of RSLR of about 3.0-4.0 mm yr<sup>-1</sup>. At each study area, we considered different transects, where we installed three measurement stations located respectively at 2.5 m, 7.5 m, and 27.5 m from the salt marsh margin. We equipped each station with an artificial marker horizon laid down on the marsh surface to measure the vertical accretion, and three sediment traps for measuring the short-term sedimentation. The material deposited in two sediment traps is collected monthly or after any single storm, whereas sediment deposited in the third trap is collected once a year, in order to compare sediment deposition dynamics at short (single storm event) and annual time scales. We measure accretion rate, grain size distribution, organic and inorganic content.</p><p>Short-term sedimentation displays a very high variability (0 – 320 g d<sup>-1</sup> m<sup>-2</sup>) highlighting the importance of particularly intense storm events in resuspending and transporting sediment from tidal flats to the salt-marsh surface. In particular, during the storm events occurred in October 2018 and November 2019, sedimentation increases significantly and displays values much higher compared to fair-weather periods. According to our analysis, sedimentation grows exponentially with daily mean inundation time. Even if the inner part of the salt marsh is characterized by lower elevation and, hence, by greater inundation time, sedimentation shows smaller values compared to the salt marsh margin, since suspended material settles close to the margin and decreases towards the inner part of the marsh.</p>

Blackriveran carbonates from the subsurface of the Lake Simcoe area, southern Ontario: stratigraphy and sedimentology of a low-energy carbonate ramp

1999 ◽  
Vol 36 (6) ◽  
pp. 871-889 ◽  
Author(s):  
Jonathan L Grimwood ◽  
Mario Coniglio ◽  
Derek K Armstrong
Keyword(s):  
Climatic Conditions ◽  
Carbonate Ramp ◽  
Low Energy ◽  
Upper Ordovician ◽  
Southern Ontario ◽  
Lake Simcoe ◽  
Homoclinal Ramp ◽  
Petrographic Study ◽  
Peritidal Carbonates

The lowest Upper Ordovician (Blackriveran) strata in the Lake Simcoe area represent the base of a major transgressive sequence of peritidal carbonates and siliciclastics. From detailed petrographic study of 12 cores that penetrate, in ascending order, the Shadow Lake, Gull River, and lower Bobcaygeon formations, seven distinctive lithofacies are recognized: (1) sandstone, siltstone, and shale; (2) dolostone and calcareous dolostone; (3) lime mudstone; (4) peloidal bioclastic wackestone and packstone; (5) peloidal bioclastic grainstone; (6) ooid grainstone; and (7) intraclastic bioclastic wackestone and packstone. Metre-scale cycles, like those reported from numerous other peritidal deposits, are apparently absent in this succession. In addition, these strata are commonly interrupted by a variety of hardgrounds. The carbonate strata can be grouped into four lithofacies associations that represent deposition in generally low energy, tropical paleoenvironments along a southward-facing, homoclinal ramp that was frequently influenced by storms. Rapid facies changes along depositional strike likely resulted from a combination of an irregular basement topography and coastline geometry. The coexistence of Heterozoan and Photozoan carbonates in the lower Bobcaygeon Formation probably reflects the increasing incorporation of cooler oceanic waters as the ramp gradually deepened during the Tippecanoe transgression rather than the onset of more temperate climatic conditions.

Lithofacies and age variation in the Fossil Hill Formation (Lower Silurian), southern Georgian Bay region, Ontario

1999 ◽  
Vol 36 (10) ◽  
pp. 1743-1762
Author(s):  
Christopher A Stott ◽  
Peter H von Bitter
Keyword(s):  
Apparent Absence ◽  
Southern Ontario ◽  
Georgian Bay ◽  
Tectonic Model ◽  
Lower Silurian ◽  
Bedded Chert ◽  
Age Variation

The Fossil Hill Formation in the southern Georgian Bay region demonstrates considerable faunal and lithological variation. Well-defined distinctions exist between bedded chert-bearing, sparsely fossiliferous, argillaceous dolostones of the formation in the eastern Beaver Valley and relatively pure, fossiliferous, non-chert-bearing dolostones observed on the nearby southern Bruce Peninsula and Cape Rich Steps. Biostratigraphic studies and lithostratigraphic tracing through the intervening Bighead Valley suggest that the Fossil Hill Formation of the eastern Beaver Valley is correlative with the typical lower Pentamerus bank and the overlying coral-stromatoporoid biostrome of late Aeronian (Llandovery C1-C2) age observed on the southern Bruce Peninsula and Cape Rich Steps. Regionally, the Fossil Hill Formation exhibits significant age variation; biostratigraphically diagnostic brachiopods (Pentamerus oblongus, Pentameroides subrectus, and Plicostricklandia castellana) from the formation near Walters Falls indicate Telychian (Llandovery C4-C6) to early Wenlock age for part of the unit there. The highly localized preservation of Fossil Hill Formation strata of Telychian age in the Walters Falls area, along with contemporaneous facies changes noted in strata of Aeronian age and the apparent absence of Fossil Hill Formation strata at other localities, suggests that the paleotopography of the southern Georgian Bay region varied markedly during the mid to late Llandovery. A tectonic model that relates epeirogenic uplift associated with the Algonquin Arch in southern Ontario to the vertical rotation of fault-bounded lithospheric blocks, and additions to the model suggested herein, may explain the observed variations.

Lower Silurian (Aeronian) megafaunal and conodont biofacies of the northwestern Michigan Basin

1997 ◽  
Vol 34 (6) ◽  
pp. 753-764 ◽  
Author(s):  
Rodney Watkins ◽  
Jeffrey J. Kuglitsch
Keyword(s):  
Tidal Flat ◽  
Continental Margins ◽  
Michigan Basin ◽  
Siliceous Sponge ◽  
Lower Silurian ◽  
The North ◽  
Conodont Biofacies ◽  
Shallow Subtidal ◽  
Sponge Spicules ◽  
Water Depths

Lower Silurian (Llandovery: Aeronian) carbonates of the Burnt Bluff Group, northwestern Michigan Basin, represent a transect along a southward-dipping ramp that extends from tidal-flat to basin environments. Benthic megafaunas include an ostracod biofacies (tidal flat), stromatoporoid–coral biofacies (very shallow subtidal), pentamerid, crinozoan, and crinozoan–stromatoporoid biofacies (deeper subtidal), and a crinozoan–sponge biofacies (distal ramp and basin). The crinozoan–sponge biofacies, which includes diverse, small crinozoan ossicles, 19 types of siliceous sponge spicules, and at least 65 other taxa, has a biota that is similar to those of Silurian continental margins. Megafaunal biofacies indicate an Early Silurian gradient going from a shoreline in the north to water depths of perhaps 60 m in the south. The Burnt Bluff Group contains conodonts of the Icriodella discreta – Icriodella deflecta zone as an onshore biofacies with Panderodus, Kockelella, Ozarkodina, Icriodella, and Oulodus, and an offshore biofacies with Panderodus, Walliserodus, and Aspelundia.

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