Present and postglacial rates of uplift for glaciated northern and eastern North America derived from postglacial uplift curves

1970 ◽  
Vol 7 (2) ◽  
pp. 703-715 ◽  
Author(s):  
J. T. Andrews
Keyword(s):  
North America ◽  
Eastern North America ◽  
Hudson Bay ◽  
High Cell ◽  
Uplift Rate ◽  
Radiocarbon Dates ◽  
Marine Deposits ◽  
Maximum Value ◽  
Current Maximum ◽  
A Current

Average rates of postglacial uplift reach a maximum value of nearly 4 m 100 y−1 over southeastern Hudson Bay, and another high cell, with rates of about 2.5 m 100 y−1, lies between Bathurst Inlet and Southampton Island. Current rates of uplift are underestimated if exponential curves are fitted solely to dated raised marine deposits without considering the amount of future recovery. Rates of rebound are, instead, derived from A/t where A is uplift in the first 1000 y since deglaciation, and t is time since deglaciation. For the northwest margin of the former ice sheet coefficients of determination for rate of uplift, at specific times, as a function of distance are [Formula: see text]. Maps of rates of uplift for northern and eastern North America are presented for 8000 y B.P., 6000 y B.P. and the present day. They reveal the existence of three uplift centers and show that rates of uplift declined from a maximum of 10 to 12 m 100 y−1, immediately following deglaciation, to a current maximum of about 1.3 m 100 y−1. Agreement is satisfactory when calculated rates of uplift are compared with those derived from geological observations, radiocarbon dates, and from water-level records. A final map shows isochrones on the uplift rate of ~1 m 100 y−1. The rate dropped to this value about 10 000 y ago on the outer northwest and southeast coasts, whereas the value might not be reached for another 2000 y in southeastern Hudson Bay.

Distribution of the middorsal stripe dimorphism in the wood frog, Rana sylvatica, in eastern North America

1980 ◽  
Vol 58 (9) ◽  
pp. 1643-1651 ◽  
Author(s):  
Frederick W. Schueler ◽  
Francis R. Cook
Keyword(s):  
United States ◽  
North America ◽  
Rana Sylvatica ◽  
Wood Frog ◽  
Eastern North America ◽  
Hudson Bay ◽  
Northeastern United States ◽  
Southern Ontario ◽  
Maritime Canada ◽  
Eurasian Species

The frequency of the middorsally striped morph of Rana sylvatica in Ontario and Manitoba varies from absence in southern Ontario to 80% on the coast of Hudson Bay, with a general value of 20–30% in the boreal forest, a rise to 50% on the forest–grassland ecotone in southern Manitoba, and a decline westward to 20% on the edge of the prairies. This morph is rare in the northeastern United States and Maritime Canada. The suggested relationship between its frequency and the "grassiness" of the background on which predators view it is reexamined, and it is suggested that a linkage with earlier transformation as demonstrated in Eurasian species may explain certain anomalies.

The Churchill kimberlite field, Nunavut, Canada: petrography, mineral chemistry, and geochronology

2008 ◽  
Vol 45 (9) ◽  
pp. 1039-1059 ◽  
Author(s):  
S. E. Zurevinski ◽  
L. M. Heaman ◽  
R. A. Creaser ◽  
P. Strand
Keyword(s):  
North America ◽  
Mantle Plume ◽  
Electron Microprobe ◽  
Mineral Chemistry ◽  
Eastern North America ◽  
Hudson Bay ◽  
Continental Extension ◽  
Group I ◽  
Hypabyssal Kimberlite ◽  
Kimberlite Field

Seventy-nine kimberlite intrusions have been identified in the Churchill Province, Nunavut, the result of an aggressive diamond exploration program by Shear Minerals Ltd. and their partners. This is one of Canada’s newest and largest kimberlite districts, situated immediately west of Hudson Bay between the communities of Rankin Inlet and Chesterfield Inlet. This study documents the occurrence of bonafide kimberlite rocks, classified as mainly sparsely macrocrystic, oxide-rich calcite evolved hypabyssal kimberlite and macrocrystic oxide-rich monticellite phlogopite hypabyssal kimberlite. Electron microprobe analyses of olivine, phlogopite, spinel, and perovskite support this petrographical classification. Low 87Sr/86Sr isotopic compositions determined from perovskite indicate a group I affinity. In addition, 27 precise U–Pb perovskite and Rb–Sr phlogopite emplacement ages have been determined for the Churchill kimberlites, indicating that magmatism spans ∼45 million years (225–170 Ma). The Churchill kimberlites belong to the NW–SE-trending corridor of Jurassic–Triassic kimberlite magmatism in eastern North America, which includes the Kirkland Lake, Timiskaming, and Attawapiskat kimberlite fields. Churchill kimberlites extend this corridor ∼800 km northwest, suggesting that the corridor may continue northwest with older kimberlites. This corridor is interpreted as the continental expression of magmatism linked to either a single or multiple mantle-plume hotspot track(s), a pattern geographically coincident with independent estimates for the timing and location of the continental extension of both the Great Meteor and Verde hotspot tracks.

scholarly journals Trace fossils on dinosaur bones reveal ecosystem dynamics along the coast of eastern North America during the latest Cretaceous

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4973
Author(s):  
Chase D. Brownstein
Keyword(s):  
North America ◽  
Marine Invertebrates ◽  
Atlantic Coastal Plain ◽  
Ecosystem Dynamics ◽  
Eastern North America ◽  
Marine Deposits ◽  
Terrestrial Vertebrate ◽  
Atlantic Coastal ◽  
Tibia Shaft

Direct evidence of paleoecological processes is often rare when the fossil record is poor, as in the case of the Cretaceous of eastern North America. Here, I describe a femur and partial tibia shaft assignable to theropods from two Late Cretaceous sites in New Jersey. The former, identifiable as the femur of a large ornithomimosaur, bears several scores interpreted as shark feeding traces. The tibia shaft has punctures and flaked bone from the bites of mid-sized crocodyliforms, the first documented occurrence of crocodyliform traces on dinosaur bone from the Maastrichtian of the Atlantic Coastal Plain. The surface of the partial tibia is also littered with indentations interpreted as the traces of invertebrates, revealing a microcosm of biological interaction on the coastal seafloor of the Cretaceous Atlantic Ocean. Massive crocodyliforms, such as Deinosuchus rugosus and the slightly smaller Deltasuchus motherali, maintained the role of terrestrial vertebrate taphonomic process drivers in eastern North America during the Cretaceous. The report of crocodyliform bite marks on the ornithomimosaur tibia shaft in this manuscript reinforces the importance of the role of crocodyliforms in the modification of terrestrial vertebrate remains during the Cretaceous in North America. The preserved invertebrate traces add to the sparse record of the presence of barnacles and other marine invertebrates on dinosaur bone, and the evidence of shark feeding on the ornithomimosaur femur support the “bloat-and-float” model of terrestrial vertebrate fossil deposition in marine deposits from the Cretaceous of eastern North America.

Regional variation in the terminal Pleistocene and early Holocene radiocarbon record of eastern North America

2013 ◽  
Vol 79 (2) ◽  
pp. 175-188 ◽  
Author(s):  
D. Shane Miller ◽  
Joseph A.M. Gingerich
Keyword(s):  
North America ◽  
Regional Variation ◽  
Probability Distributions ◽  
Younger Dryas ◽  
Eastern North America ◽  
Northeastern United States ◽  
Radiocarbon Dates ◽  
Terminal Pleistocene ◽  
The Relationship ◽  
Data Result

AbstractIn this paper we use radiocarbon dates to evaluate the signature of the Younger Dryas Chronozone (YDC) in eastern North America. Using an approach that examines radiocarbon dates by region, we argue that the northeastern United States shows a better overall representation of radiocarbon dates when compared to the Mid-Atlantic and Southeast. These data result in a peak in summed probability distributions during the YDC, which is often interpreted as evidence of population growth. Further examination of these distributions, however, illustrates that differential standard deviations, varying sample size, and the effect of taphonomic and research biases likely overwhelm any demographic signatures in our study sample. Consequently, the frequency of radiocarbon dates by itself is insufficient for understanding the relationship between climate, culture and demography in eastern North America.

Some Amerasian Pottery Traits in North Asian Prehistory

1953 ◽  
Vol 19 (1) ◽  
pp. 25-39 ◽  
Author(s):  
Paul Tolstoy
Keyword(s):  
United States ◽  
North America ◽  
New World ◽  
The United States ◽  
Eastern North America ◽  
Eastern Siberia ◽  
Radiocarbon Dates ◽  
Old World ◽  
The Subject

Asiatic origins have, at one time or another, been suggested or at least considered for a number of traits connected with the manufacture and decoration of the earlier New World pottery. The well-known paper by McKern (1937) is among the most explicit statements on the subject. Griffin (1946; Sears and Griffin 1950a) has held similar views for some time. Like McKern, he has primarily in mind traits of the Woodland pattern of eastern North America, although he also mentions some non-Woodland traits among those which have counterparts in the Old World (1946, p. 45).Since McKern's paper, the distribution in time of the traits involved has become a lot better established. With the help of the still suspiciously regarded radiocarbon dates, our perspective on ceramic history in the United States has been extended over a span which appears to be that of some four millennia. Among the more significant additions to the Asiatic half of the distributional picture first place must be given to recent Soviet work in eastern Siberia.

scholarly journals Sangamon and Pre-Sangamon Interglaciations in the Hudson Bay Lowlands of Manitoba

2007 ◽  
Vol 44 (3) ◽  
pp. 319-336 ◽  
Author(s):  
Lynda A. Dredge ◽  
Alan V. Morgan ◽  
Erik Nielsen
Keyword(s):  
High Pressure ◽  
North America ◽  
Global Change ◽  
Hudson Bay ◽  
Present Position ◽  
Radiocarbon Dates ◽  
Glacial Sediments ◽  
Hudson Bay Lowlands ◽  
The World ◽  
Beetle Assemblages

ABSTRACT The manuscript documents voluminous new and published stratigraphie and paléontologie data from a region unique in North America, and possibly the world, in that it has abundant natural exposures recording a long and consistent succession of Quaternary tills and fossiliferous intertill sediments. Two major non-glacial intervals have been recognized under tills. Various non-glacial sediments have been correlated using their stratigraphie position, pollen analysis, and beetle assemblages, and are found to be equivalent to the Missinaibi Formation in Ontario. Non-finite high pressure radiocarbon dates, and aspartic acid ratios on wood suggest that the uppermost and most prevalent interval is of Sangamonian age. The Sangamonian record begins and ends with cool intervals, separated by a warmer period when climates were similar to or slightly warmer than present, and when the northern treeline was near its present position. The interval began with a high glacioisostatic sea, which regressed to levels below present Hudson Bay datum. The Sundance paleosol and silt beds below the Amery till relate to an earlier interglaciation characterized by cool tundra conditions. As an analogue for predicting future global change, the record preserved in the Hudson Bay Lowlands is second to none: additional intensive research is strongly recommended.

The Contemporary Distribution of Pollen in Eastern North America: A Comparison with the Vegetation

1975 ◽  
Vol 5 (3) ◽  
pp. 395-434 ◽  
Author(s):  
Ronald B. Davis ◽  
Thompson Webb
Keyword(s):  
North America ◽  
Boreal Forest ◽  
Deciduous Forest ◽  
Eastern North America ◽  
Hudson Bay ◽  
Southeastern Part ◽  
Forest Tundra ◽  
Continental Scale ◽  
Modern Pollen ◽  
Pollen Types

By mapping and summarizing 478 pollen counts from surface samples at 406 locations in eastern North America, this study documents the relationships between the distributions of pollen and vegetation on a continental scale. The most common pollen types in this region are pine, birch, oak, and spruce. Maps showing isopercentage contours or isopolls for 13 important pollen types reflect the general N-S zonation of the vegetation. The maps and tabulations of average pollen spectra for the six major vegetational regions indicate high values for the following pollen types in each region: (1) tundra-nonarboreal birch, sedge, and alder; (2) forest/tundra-spruce, nonarboreal birch and alder; (3) boreal forest-spruce, jack pine (type), and arboreal birch with fir in the southeastern part; (4) conifer/hardwood forest-white pine, arboreal birch, and hemlock with beech, maple, and oak in the southern part; (5) deciduous forest-oak, pine, hickory, and elm, with beech and maple in the northern part, and highest values of oak and hickory west of the Appalachian crest; and (6) southeastern forest-pine, oak, hickory, tupelo, and Myricaceae. In some cases, less abundant pollen types are diagnostic for the region, e.g., bald cypress in the southeast. In the conifer-hardwood region and southward, pollen of weeds associated with deforestation and agriculture is abundant. The maps also show that much of southeastern U.S. and the area just to the east of Hudson Bay are in need of additional sampling. At 51 of the sites, absolute pollen frequencies (APF; grains/ml lake sediment) were obtained. These confirm the major conclusions from the percentage data, but differences are evident, e.g., the percentages of alder pollen peak in the tundra whereas alder APFs peak in the boreal forest, and spruce percentages peak in the forest-tundra whereas spruce APFs peak in the boreal forest. Because the APF data reflect the patterns of absolute abundance of individual taxa in the vegetation as well as the overall forest densities, future counts of modern pollen should include APF determinations. The effects of sedimentation processes on APF quantities indicate that APF samples should be obtained from moderate size lakes of similar morphology and hydrology and that, in each lake, several samples from the profundal zone should be pooled to create a sample representative of that lake.

Focusing on the Old Wood Problem: A Response to Hart and Nolan

2015 ◽  
Vol 80 (3) ◽  
pp. 613-614
Author(s):  
Robert A. Cook ◽  
Aaron R. Comstock
Keyword(s):  
North America ◽  
Wood Charcoal ◽  
Eastern North America ◽  
Ohio Valley ◽  
Radiocarbon Dates ◽  
Analytical Errors

Our recent paper demonstrated that radiocarbon assays sampled from wood charcoal were not systematically skewed when compared to non-wood samples from the same site. This suggests that the “old wood” problem may not be quite as problematic in the temperate Middle Ohio Valley as many suspect. In their comment, Hart and Nolan missed our broader point and mischaracterized our findings. Specifically, we did not suggest that our findings apply to the entirety of eastern North America, nor did we make analytical errors. A thorough reading of our paper clearly supports the following rebuttal. Our main point is that scholars should think twice before discarding radiocarbon dates from wood charcoal, for in some contexts they are the most useful means of determining important chronological information. Despite the suggestion to the contrary, “old wood” concerns do form elements of several hygiene protocols, including Nolan's (2012).

Parastrophinella (Brachiopoda): Its paleogeographic significance at the Ordovician/Silurian boundary

1997 ◽  
Vol 71 (3) ◽  
pp. 369-380 ◽  
Author(s):  
Jisuo Jin ◽  
Paul Copper
Keyword(s):  
North America ◽  
Type Species ◽  
Late Ordovician ◽  
Eastern North America ◽  
Hudson Bay ◽  
Morphologic Change ◽  
Baffin Island ◽  
Median Septum ◽  
Lamellar Layer ◽  
Anticosti Island

The type species of Parastrophinella, P. reversa, a pentamerid brachiopod from the uppermost Ordovician (Hirnantian) Ellis Bay Formation of Anticosti Island, Quebec, shows that the genus is characterized by three features: 1) a ventral median septum apically buried in a thickened valve floor, but anteriorly rising above valve floor; 2) prominent alate plates, which are homologous to brachial processes; and, 3) a pseudocruralium consisting of a dorsal median septum, which is largely buried in the valve floor posteriorly, and outer plates that are connected to the median septum via prismatic substance (with poorly developed lamellar layer at the junctions) at, or slightly above, the valve floor. These constitute criteria by which many species previously assigned to Parastrophinella are excluded from the genus. Late Ordovician species that fit the redefinition of Parastrophinella are now confined to eastern North America. The genus crosses the Ordovician/Silurian boundary without major morphologic change, and Early Silurian species of Parastrophinella occur in both eastern North America and Great Britain. In the Late Ordovician, the pentamerid fauna of North America (Laurentia) contrasted sharply with that of Baltica and Kazakhstan, where the Holorhynchus fauna was dominant. Typical elements of the Holorhynchus fauna, such as the large-shelled Holorhynchus and Proconchidium, are known only in the northern parts of Laurentia (Baffin Island, Greenland, and Kolyma), and are absent in the Hudson Bay and Williston basins and southwards.

Alligator Mound: Geoarchaeological and Iconographical Interpretations of a Late Prehistoric Effigy Mound in Central Ohio, USA

2003 ◽  
Vol 13 (2) ◽  
pp. 147-167 ◽  
Author(s):  
Bradley T. Lepper ◽  
Tod A. Frolking
Keyword(s):  
North America ◽  
Late Woodland ◽  
Eastern North America ◽  
Late Prehistoric ◽  
Radiocarbon Dates ◽  
Archaeological Investigation ◽  
Fort Ancient ◽  
Effigy Mound

Alligator Mound is an animal effigy mound in central Ohio, USA. Since Ephraim Squier and Edwin Davis first recorded and mapped it in 1848, many have speculated regarding its age and meaning, but with remarkably little systematic archaeological investigation. Many scholars have assumed the Hopewell culture (c. 100 BC-AD 400) built the mound, based principally on its proximity to the Newark Earthworks. The Hopewell culture, however, is not known to have built other effigy mounds. Limited excavations in 1999 revealed details of mound stratigraphy and recovered charcoal embedded in mound fill near the base of the mound. This charcoal yielded radiocarbon dates that average between AD 1170 and 1270, suggesting that the Late Prehistoric Fort Ancient culture (c. AD 1000-1550) made the mound. This result coincides with dates obtained for Serpent Mound in southern Ohio and suggests that the construction of effigy mounds in eastern North America was restricted to the Late Woodland and Late Prehistoric traditions. Ethnographic and ethnohistoric analogies suggest that the so-called 'Alligator' might actually represent the Underwater Panther and have served as a shrine for invoking the aid of supernatural powers.

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