Precambrain Fault Systems as Control on Regional Differences in Relative Sea Level Along the Early Ordovician Platform of Eastern North America

2006 ◽  
Vol 76 (4) ◽  
pp. 700-716 ◽  
Author(s):  
O. Salad Hersi ◽  
G. R. Dix
Keyword(s):  
North America ◽  
Sea Level ◽  
Regional Differences ◽  
Eastern North America ◽  
Relative Sea Level ◽  
Early Ordovician ◽  
Fault Systems

Widespread Late Devonian marine anoxia in eastern North America: a case study of the Kettle Point Formation black shale, southwestern Ontario

2016 ◽  
Vol 53 (8) ◽  
pp. 837-855 ◽  
Author(s):  
Nikole Bingham-Koslowski ◽  
Cameron Tsujita ◽  
Jisuo Jin ◽  
Karem Azmy
Keyword(s):  
North America ◽  
Sea Level ◽  
Black Shale ◽  
Black Shales ◽  
Shallow Waters ◽  
Eastern North America ◽  
Late Devonian ◽  
Red Beds ◽  
Relative Sea Level ◽  
Organic Rich Sediment

The Kettle Point Formation of southwestern Ontario consists of intervals of organic-rich interlaminated black shale interbedded with organic-poor greyish green mudstones and rare red beds, separated by metre-scale sequences of non-interlaminated black shale. The formation shows a largely consistent background value for the black shales around −20‰ δ34S, punctuated by a substantial positive excursion of ∼32‰ (up to +12.87‰) that coincides with a significant interval of greyish green mudstone and red beds. Lithological and geochemical data indicate that the black shales were deposited during periods of anoxia, with thick intervals of non-interlaminated black shales recording the peak of anoxia, whereas the greyish green mudstones record deposition in more oxygenated environments. Relative water depth is interpreted as the key control on the vertical and lateral distribution of the Kettle Point lithofacies. Interbedded black shales and greyish green mudstones were deposited in relatively shallow waters, where minor, short-lived falls in relative sea level promoted dysoxic to oxic conditions and the deposition of organic-poor lithologies. Non-interlaminated black shales are indicative of substantial rises in relative sea level, resulting in widespread anoxia and the deposition of thicker and more laterally extensive packages of organic-rich sediment. The formation of black shales in relatively shallow waters in southwestern Ontario implies that the extensive deposition of organic-rich sediment across eastern North America during the Late Devonian was a product of widespread anoxia related to restricted circulation in intracratonic and foreland basin depositional centers.

A radiocarbon chronology of Holocene climate change and sea-level rise at the Delmarva Peninsula, US Mid-Atlantic Coast

The Holocene ◽  
2021 ◽  
pp. 095968362110482
Author(s):  
Kelvin W Ramsey ◽  
Jaime L. Tomlinson ◽  
C. Robin Mattheus
Keyword(s):  
Climate Change ◽  
North America ◽  
Sea Level Rise ◽  
Sea Level ◽  
Early Holocene ◽  
Eastern North America ◽  
Delmarva Peninsula ◽  
The Holocene ◽  
Cool Climate ◽  
And Sea Level

Radiocarbon dates from 176 sites along the Delmarva Peninsula record the timing of deposition and sea-level rise, and non-marine wetland deposition. The dates provide confirmation of the boundaries of the Holocene subepochs (e.g. “early-middle-late” of Walker et al.) in the mid-Atlantic of eastern North America. These data record initial sea-level rise in the early Holocene, followed by a high rate of rise at the transition to the middle Holocene at 8.2 ka, and a leveling off and decrease in the late-Holocene. The dates, coupled to local and regional climate (pollen) records and fluvial activity, allow regional subdivision of the Holocene into six depositional and climate phases. Phase A (>10 ka) is the end of periglacial activity and transition of cold/cool climate to a warmer early Holocene. Phase B (10.2–8.2 ka) records rise of sea level in the region, a transition to Pinus-dominated forest, and decreased non-marine deposition on the uplands. Phase C (8.2–5.6 ka) shows rapid rates of sea-level rise, expansion of estuaries, and a decrease in non-marine deposition with cool and dry climate. Phase D (5.6–4.2 ka) is a time of high rates of sea-level rise, expanding estuaries, and dry and cool climate; the Atlantic shoreline transgressed rapidly and there was little to no deposition on the uplands. Phase E (4.2–1.1 ka) is a time of lowering sea-level rise rates, Atlantic shorelines nearing their present position, and marine shoal deposition; widespread non-marine deposition resumed with a wetter and warmer climate. Phase F (1.1 ka-present) incorporates the Medieval Climate Anomaly and European settlement on the Delmarva Peninsula. Chronology of depositional phases and coastal changes related to sea-level rise is useful for archeological studies of human occupation in relation to climate change in eastern North America, and provides an important dataset for future regional and global sea-level reconstructions.

Glacial Isostatic Adjustment with 3D Earth models: A comparison of case studies of deglacial relative sea level records of North America and Russian Arctic

2020 ◽  
Author(s):  
Tanghua Li ◽  
Nicole Khan ◽  
Simon Engelhart ◽  
Alisa Baranskaya ◽  
Peltier William ◽  
...  
Keyword(s):  
North America ◽  
Sea Level ◽  
3D Models ◽  
Viscosity Model ◽  
Glacial Isostatic Adjustment ◽  
Russian Arctic ◽  
Scaling Factors ◽  
Relative Sea Level ◽  
Isostatic Adjustment ◽  
Best Fit

<p>The Canadian landmass of North America and the Russian Arctic were covered by large ice sheets during the Last Glacial Maximum, and have been key areas for Glacial Isostatic Adjustment (GIA) studies. Previous GIA studies have applied 1D models of Earth’s interior viscoelastic structure; however, seismic tomography, field geology and recent studies reveal the potential importance of 3D models of this structure. Here, using the latest quality-controlled deglacial sea-level databases from North America and the Russian Arctic, we investigate the effects of 3D structure on GIA predictions. We explore scaling factors in the upper mantle (<em>β<sub>UM</sub></em>) and lower mantle (<em>β<sub>LM</sub></em>) and the 1D background viscosity model (<em>η<sub>o</sub></em>) with predictions of of the ICE-6G_C (VM5a) glaciation/deglaciation model of Peltier et al (2015, JGR) in these two regions, and compare with the best fit 3D viscosity structures.</p><p>We compute gravitationally self-consistent relative sea-level histories with time dependent coastlines and rotational feedback using both the Normal Mode Method and Coupled Laplace-Finite Element Method. A subset of 3D GIA models is found that can fit the deglacial sea-level databases for both regions. These databases cover both the near and intermediate field regions. However, North America and Russian Arctic prefer different 3D structures (i.e., combinations of (<em>η<sub>o</sub>, β<sub>UM</sub>, β<sub>LM</sub></em>)) to provide the best fits. The Russian Arctic database prefers a softer background viscosity model (<em>η<sub>o</sub></em>), but larger scaling factors (<em>β<sub>UM</sub>, β<sub>LM</sub></em>) than those preferred by the North America database.</p><p>Outstanding issues include the uncertainty of the history of local glaciation history. For example, preliminary modifications of the ice model in Russian Arctic reveal that the misfits of 1D models can be significantly reduced, but still fit less well than the best fit 3D GIA model.An additional issue concerns the extent to which the 3D models are able to improve both fits in North America and Russian Arctic when compared with 1D internal structure (ICE-6G_C VM5a & ICE-7G VM7), will be assessed in a preliminary fashion.</p>

North American Deglacial Marine- and Lake-Limit Surfaces*

2007 ◽  
Vol 59 (2-3) ◽  
pp. 155-185 ◽  
Author(s):  
Arthur S. Dyke ◽  
Lynda A. Dredge ◽  
Douglas A. Hodgson
Keyword(s):  
North America ◽  
Sea Level Rise ◽  
Sea Level ◽  
North American ◽  
Ice Sheet ◽  
Glacial Lake ◽  
Limit Surface ◽  
Relative Sea Level ◽  
Level Curves ◽  
Recent Synthesis

Abstract The deglacial marine-limit surface is a virtual topography that shows the increase of elevation since deglaciation. The currently available set of marine-limit elevations (n = 929), about three times the number available in the most recent synthesis, allows a fairly detailed rendering of the surface across most of glaciated North America and Greenland. Certain large glacial lake-limit surfaces are analogous to marine-limit surfaces, except that their gradients were not dampened by eustatic sea-level rise. Collectively the surfaces reflect both gross ice-sheet geometry and regional to local rates of ice-marginal recession. As such, they are replication targets for glacioisostatic modelling that are supplementary to and more continuously distributed than relative sea-level curves.

Sign in / Sign up

Export Citation Format

Share Document