scholarly journals Reconstructing sea-level change from the internal architecture of stromatolite reefs: an example from the Mesoproterozoic Sulky Formation, Dismal Lakes Group, arctic Canada

2006 ◽  
Vol 43 (6) ◽  
pp. 653-669 ◽  
Author(s):  
Linda C Kah ◽  
Julie K Bartley ◽  
Tracy D Frank ◽  
Timothy W Lyons
Keyword(s):  
Sea Level ◽  
Higher Order ◽  
Growth Patterns ◽  
Complex Nature ◽  
Arctic Canada ◽  
Reef Complex ◽  
Sea Level Fluctuations ◽  
Subaerial Exposure ◽  
Dramatic Rise ◽  
Internal Architecture

The Mesoproterozoic Dismal Lakes Group, arctic Canada, contains a relatively thin, yet regionally extensive stromatolitic reef complex that developed subtidally during a major transgression, shoaled to sea level, and was overlain by intertidal to supratidal carbonate and evaporite strata. The September Lake reef complex exhibits a complex internal architecture that records the interaction between stromatolite growth and changes in accommodation space derived from both higher order (4th- or 5th-order, parasequence-scale) changes in sea level and the variable bathymetry of the sea floor. Reef growth, which was initiated during three sea-level cycles, records progressive marine transgression over depositional lows that were formed during pre-reef subaerial exposure and erosion of the underlying strata. A fourth sea-level cycle, represented by spectacular coniform stromatolites with >10 m of synoptic relief, marks a more dramatic rise in sea level and establishment of the main reef complex. Aggradation and eventual shoaling of the reef complex occurred over an additional six sea-level cycles. Only basinward regions of the September Lake reef complex preserve vertical stacking of reefal packages in response to sea-level fluctuations. In contrast, in the main reef core, sea-level fluctuations resulted in subaerial exposure of the reef top, variable karst development, and the progressive infilling of reef topography by progradational reef elements. Assessment of stromatolite growth patterns reveals the complex nature of the reef architecture and permits the determination of higher order changes in relative sea level that were responsible for reef development.

The Ordovician–Silurian boundary on Cornwallis and Truro islands, Arctic Canada: preliminary data

1991 ◽  
Vol 28 (11) ◽  
pp. 1854-1862 ◽  
Author(s):  
Michael J. Melchin ◽  
Alexander D. McCracken ◽  
Fred J. Oliff
Keyword(s):  
Sea Level ◽  
Arctic Canada ◽  
Faunal Turnover ◽  
Sea Level Fluctuations ◽  
Continuous Sequence ◽  
Cape Phillips Formation ◽  
Show Evidence ◽  
Conodont Zone ◽  
Continuous Sedimentation ◽  
Cornwallis Island

Four sections of the lower part of the Cape Phillips Formation, two outcrops on northeastern Cornwallis Island and one outcrop and one drill core from Truro Island, Northwest Territories, Canada, provide significant new data on the Ordovician–Silurian boundary. They show evidence of continuous sedimentation through the boundary interval and a continuous sequence of graptolite zones, including the bohemicus and persculptus zones, which have not been previously found in Arctic Canada. Strata yield graptolites, including uncompressed specimens, and conodonts through most of the sections. The ordovicicus conodont Zone occurs within the pacificus to lower persculptus graptolite zones. The nathani conodont Zone contains a "transitional fauna," a mixing of species typical of the preceeding ordovicicus Zone and those generally regarded as Silurian indicators. This conodont zone ranges from the middle of the persculptus graptolite Zone into the lower acuminatus graptolite Zone and, thus, spans the Ordovician–Silurian boundary. The Ordovician–Silurian faunal turnover of the conodonts, therefore, also spans the Ordovician–Silurian boundary and is not coincident with the interval of major graptolite extinction, which occurs earlier, at the end of the pacificus Zone. The base of the kentuckyensis conodont Zone occurs in the acuminatus graptolite Zone. Sedimentologic evidence of the maximum eustatic sea-level drop can be seen within the bohemicus Zone (early Hirnantian) and possibly one or several smaller scale sea-level fluctuations through the underlying zones.

scholarly journals Određivanje novih pliocenskih, pleistocenskih i holocenskih litostratigrafskih jedinica u hrvatskom dijelu Jadrana (priobalju)

Geoadria ◽  
2015 ◽  
Vol 20 (2) ◽  
Author(s):  
Tomislav Malvić ◽  
Josipa Velić ◽  
Marko Cvetković ◽  
Marko Vekić ◽  
Marijan Šapina
Keyword(s):  
Sea Level ◽  
River Sediments ◽  
Channel Formation ◽  
Po River ◽  
Northern Adriatic ◽  
Sea Level Fluctuations ◽  
Subaerial Exposure ◽  
Lithostratigraphic Units ◽  
Glacial Periods

Exploration of Pliocene, Pleistocene and Holocene deposits in of the Croatian Northern Adriatic and Southern Dalmatia (coastline) offshore is presented in this paper. It was a way to describe the existing lithostratigraphic units in Croatian Po River sediments and to determine such units in the depositional area of Neretva River. Both systems have been influenced by sea-level fluctuations during the Quaternary, resulting in significantly decreased sea depths and increased subaerial exposure during glacial periods, especially in the Northern Adriatic. In the Croatian part of Po Depression, two new formations were mentioned – Istria (Pliocene) and Ivana (Pleistocene, Holocene). Three new lithostratigraphic members were described within Ivana Formation, namely Anamarija, Katarina and Izabela. Further south, in the Southern Dalmatia shallow offshore, Pliocene, Pleistocene and Holocene deposits were named the new Neretva Channel Formation. This formation was further divided into Neretva Sands (sometimes equivalent for entire formation) and the (Quaternary) Mali Ston Bay Member. No typical Pliocene lithotype has yet been recognised.

scholarly journals On the peritidal cycles and their diagenetic evolution in the Lower Jurassic carbonates of the Calcare Massiccio Formation (Central Apennines)

2015 ◽  
Vol 66 (5) ◽  
pp. 393-407 ◽  
Author(s):  
Marco Brandano ◽  
Laura Corda ◽  
Laura Tomassetti ◽  
Davide Testa
Keyword(s):  
Sea Level ◽  
High Frequency ◽  
Environmental Changes ◽  
Lower Jurassic ◽  
Type I ◽  
Central Apennines ◽  
Sea Level Fluctuations ◽  
Subaerial Exposure ◽  
Orbital Cycles ◽  
Diagenetic Evolution

Abstract This paper shows the environmental changes and high-frequency cyclicity recorded by Lower Jurassic shallow-water carbonates known as the Calcare Massiccio Formation which crop out in the central Apennines of Italy. Three types of sedimentary cycle bounded by subaerial erosion have been recognized: Type I consists of a shallowing upward cycle with oncoidal floatstones to rudstones passing gradationally up into peloidal packstone alternating with cryptoalgal laminites and often bounded by desiccation cracks and pisolitic-peloidal wackestones indicating a period of subaerial exposure. Type II shows a symmetrical trend in terms of facies arrangement with peloidal packstones and cryptoalgal laminites present both at the base and in the upper portion of the cycle, separated by oncoidal floatstones to rudstones. Type III displays a shallowing upward trend with an initial erosion surface overlain by oncoidal floatstones to rudstones that, in turn, are capped by pisolitic-peloidal wackestones and desiccation sheet cracks. Sheet cracks at the top of cycles formed during the initial phase of subaerial exposure were successively enlarged by dissolution during prolonged subaerial exposure. The following sea-level fall produced dissolution cavities in subtidal facies, while the successive sea-level rise resulted in the precipitation of marine cements in dissolution cavities. Spectral analysis revealed six peaks, five of which are consistent with orbital cycles. While a tectonic control cannot be disregarded, the main signal recorded by the sedimentary succession points toward a main control related to orbital forcing. High frequency sea-level fluctuations also controlled diagenetic processes.

Quaternary Sea Level Fluctuations on a Tectonic coast: New 230Th/234U Dates from the Huon Peninsula, New Guinea

1974 ◽  
Vol 4 (2) ◽  
pp. 185-205 ◽  
Author(s):  
A.L. Bloom ◽  
W.S. Broecker ◽  
J.M.A. Chappell ◽  
R.K. Matthews ◽  
K.J. Mesolella
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
New Guinea ◽  
Tectonic Uplift ◽  
Reef Complex ◽  
Sea Level Fluctuations ◽  
Uplift Rates ◽  
The Mean ◽  
The Difference ◽  
The Individual

Emerged coral reef terraces on the Huon Peninsula in New Guinea were reported in a reconnaissance dating study by Veeh and Chappell 1970. Age definition achieved was not good for several important terraces, and we report here a series of new 230Th/234U dates, which further clarify the history of late Quaternary eustatic sea level fluctuations. More than 20 reef complexes are present, ranging well beyond 250,000 yr old: we are concerned with the seven lowest complexes. Major reef-building episodes dated by 30Th/234U are reef complex I at 5–9 ka (kilo anno = 1000 yr), r.c. IIIb at 41 ka (four dates), r.c. IV at 61 ka (four dates), r.c. V at 85 ka (two dates), r.c. VI at 107 ka (two dates), and r.c. VII at 118–142 ka. Complex II was previously dated by 14C at 29 ka: this age has not yet been confirmed, and may be only a lower limit. The reef crests were built during or immediately before intervals of sea level maxima, when rates of rising sea level and tectonic uplift briefly coincided. The culmination of each reef-building episode was only a few thousand years in duration, and multiple dates from the same reef complex generally group within the statistical errors of the individual dates.Several methods can be used to estimate the altitude of each sea level maximum relative to present sea level. The least complicated is to calculate mean tectonic uplift rate for each profile of the terraces, and use the mean rate to calculate the tectonic displacement of each dated reef complex on that profile. The difference between the present altitude of a reef complex and its calculated tectonic uplift gives the paleosea level at the time the reef grew. We estimate uplift rates for six surveyed sections by calibrating against published paleosea level estimates from Barbados and elsewhere, viz 125 ka, paleosea at +6 m; 103 ka, −15 m; 82 ka, −13 m. For each section the individual uplift rates for reefs V, VI, and VIIb are within 5% of their section means. Using the mean rates. paleosea level estimates for reef crests II, IIIB, and IV are made for each section. Consistency of estimates between sections is good, giving −28 m for the 60 ka paleosea level, around −38 m for the 42 ka level and −41 m for the 28 ka level (if the age is older the paleosea level would be lower. Using the mean uplift rates, the 82 ka and 103 ka paleosea levels are also estimated for each section: all individual estimates are plotted graphically, and a sea level curve drawn. The reef stratigraphy indicates sea level lowerings between each dated reef crest: the crests probably represent the interstadials of the Wisconsin (Würm, Weichsel) Glaciation, and intervening lower levels correspond to stadials. Since the last time of eustatic sea level higher than the present (about 125 ka), five sea level maxima occurred at roughly 20-ka intervals, none being as high as the present.

scholarly journals Spatial distribution of water level impact to back-barrier bays

2018 ◽  
Author(s):  
Alfredo L. Aretxabaleta ◽  
Neil K. Ganju ◽  
Zafer Defne ◽  
Richard P. Signell
Keyword(s):  
Water Level ◽  
Sea Level ◽  
Water Levels ◽  
Analytical Models ◽  
Barnegat Bay ◽  
Sea Level Fluctuations ◽  
Flooding Hazard ◽  
Short Period ◽  
Inlet Geometry ◽  
Spatial Estimates

Abstract. Water level in semi-enclosed bays, landward of barrier islands, is mainly driven by offshore sea level fluctuations that are modulated by bay geometry and bathymetry, causing spatial variability in the ensuing response (transfer). Local wind setup can have a secondary role that depends on wind speed, fetch, and relative orientation of the wind direction and the bay. Inlet geometry and bathymetry primarily regulate the magnitude of the transfer between open ocean and bay. Tides and short-period offshore oscillations are more damped in the bays than longer-lasting offshore fluctuations, such as storm surge and sea level rise. We compare observed and modeled water levels at stations in a mid-Atlantic bay (Barnegat Bay) with offshore water level proxies. Observed water levels in Barnegat Bay are compared and combined with model results from the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system to evaluate the spatial structure of the water level transfer. Analytical models based on the dimensional characteristics of the bay are used to combine the observed data and the numerical model results in a physically consistent approach. Model water level transfers match observed values at locations inside the Bay in the storm frequency band (transfers ranging from 70–100 %) and tidal frequencies (10–55 %). The contribution of frequency-dependent local setup caused by wind acting along the bay is also considered. The approach provides transfer estimates for locations inside the Bay where observations were not available resulting in a complete spatial characterization. The approach allows for the study of the Bay response to alternative forcing scenarios (landscape changes, future storms, and rising sea level). Detailed spatial estimates of water level transfer can inform decisions on inlet management and contribute to the assessment of current and future flooding hazard in back-barrier bays and along mainland shorelines.

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