A comparison of Eastern North America and Coastal New England magma suites: implications for subcontinental mantle evolution and the broad-terrane hypothesis

2005 ◽  
Vol 42 (9) ◽  
pp. 1571-1587 ◽  
Author(s):  
Michael J Dorais ◽  
Matthew Harper ◽  
Susan Larson ◽  
Hendro Nugroho ◽  
Paul Richardson ◽  
...  
Keyword(s):  
North America ◽  
New England ◽  
Trace Element ◽  
Crustal Contamination ◽  
Flood Basalt ◽  
Incompatible Trace Element ◽  
Eastern North America ◽  
Mantle Evolution ◽  
Isotopic Compositions ◽  
Maritime Canada

New England and Maritime Canada host two major suites of Mesozoic diabase dykes. The oldest is the Coastal New England dykes that were emplaced between 225 and 230 Ma. These rocks are dominantly alkaline with trace element and isotopic compositions indicative of a high-238U/204Pb mantle (HIMU) source. The oldest of the ~200 Ma Mesozoic rift magmas is represented by the Talcott basalt of the Hartford basin and its feeder dykes. External to the basin is the compositionally equivalent Higganum dyke. The extension of the Higganum, the Onway dyke in New Hampshire, is identical in major and trace element and isotopic compositions indicating that the dyke system represented a feeder to flows of flood basalt proportions. The Talcott system rocks have some trace element similarities with arc basalts and have been interpreted as representing melts of a subduction zone modified mantle beneath the Laurentian- Gondwanan suture. Incompatible trace element ratios and Ba, Th, and U values are, however, unlike arc basalts and are more indicative of crustal contamination of the primary magma. The coastal New England magmas have oceanic island basalt signatures that are generally thought to represent plume-tail magmatism, which is antithetic to a plume-head origin for the younger eastern North America magmas. However, coastal New England rocks have the same trace element signatures as the alkaline rocks of the Loihi seamount, which represent the pre-shield stage to the voluminous tholeiitic magmatism in Hawaii.

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.

A taxonomic reevaluation of North American Daphnia (Crustacea: Cladocera). III. The D. catawba complex

1997 ◽  
Vol 75 (8) ◽  
pp. 1254-1261 ◽  
Author(s):  
Paul D. N. Hebert ◽  
Terrie L. Finston
Keyword(s):  
North America ◽  
New England ◽  
Common Ancestor ◽  
Genotypic Diversity ◽  
Species Boundaries ◽  
Eastern North America ◽  
Eastern Canada ◽  
Cyclic Parthenogenesis ◽  
Forest Regions ◽  
Daphnia Catawba

Despite the importance of Daphnia in freshwater zooplankton assemblages, species boundaries in the genus are unclear. This study verifies the taxonomic validity of D. catawba by establishing its genetic divergence from other species of Daphnia that occur in eastern North America. In addition, it reveals the presence of a second, closely allied species, D. minnehaha, which had previously been placed in synonomy with D. pulex. Daphnia catawba and D. minnehaha share a preference for acidic habitats and are restricted to the deciduous and boreal forest regions of the eastern portion of the continent, where D. catawba is restricted to lakes, while D. minnehaha occurs in ponds. Both species reproduce by cyclic parthenogenesis and, based on the extent of their allozyme differentiation, last had a common ancestor more than 7 million years ago. Populations of D. minnehaha fall into two genetic clades; those from the Great Lakes watershed are morphologically divergent and have much lower levels of genotypic diversity than those from eastern Canada and the New England states.

Relative contribution of crust and mantle to flood basalt magmatism, Mahabaleshwar area, Deccan Traps

1984 ◽  
Vol 310 (1514) ◽  
pp. 627-641 ◽  
Keyword(s):  
Trace Element ◽  
Incompatible Element ◽  
Crustal Contamination ◽  
Flood Basalt ◽  
Oceanic Islands ◽  
Magma Type ◽  
Relative Contribution ◽  
History Of ◽  
Crustal Contribution ◽  
Element Enrichment

The 1200 m section of flat-lying basalts in the Mahabaleshwar area is divided into three formations on the basis of the trace elements Sr, Ba, Rb, Zr and Nb. The lowermost unit, the Poladpur Formation, is characterized by high Ba, Rb, and Zr/Nb, and low Sr. These features are accompanied by high K and Si, high and variable 87 Sr/ 86 Sr initial ratios (0.7043 - 0.7196), and low and variable e N d values (+ 2.6 to -17.4). The formation is interpreted as having developed by contamination of the overlying Ambenali magma-type with ancient granitic crust, with simultaneous fractionation of a gabbroic mineral assemblage. The more basic members of the formation are found towards the base of the succession and are more contaminated than the upper flows. The succeeding Ambenali Formation, characterized by the Ambenali magma type, has low Ba, Rb, Sr and Zr/Nb, and low and rather uniform 87 Sr/ 86 Sr initial ratios (0.7038-0.7043) coupled with high and relatively uniform e N d (+4.7 to +6.4). It is interpreted as being essentially uncontaminated and derived from a mantle source with a history of slight trace-element enrichment relative to m.o.r.b.-source. The uppermost group of flows, the Mahabaleshwar Formation, is, like the Poladpur, enriched in Ba, Rb, K and Si relative to the Ambenali, but has lower Zr/Nb and higher Sr. 87 Sr/ 86 Sr initial ratios (0.7040-0.7056) are slightly higher than in the Ambenali, and e N d lies in the range +7.1 to -3.0. In this formation Sr correlates positively with the other incompatible elements and with 87 Sr/ 86 Sr initial ratios. This is in strong contrast to the relations observed in the Poladpur, and we believe that the behaviour of Sr may be a simple pointer to the distinction between mantle and crustal contributions. Assuming that late-stage crystal fractionation processes can be allowed for, if Sr correlates positively with elements such as K, Rb and Ba then mantle enrichment processes are clearly implied. Conversely, as for example in the Poladpur, if the correlation is negative, crustal contamination is suspected because Sr is unlikely to behave as an incompatible element in most crustal derived melts or fluids because of buffering by residual plagioclase. Furthermore, the relative uniformity of the Mahabaleshwar Formation, the position on the Sr and Nd isotope diagram close to the ‘mantle array’, the fact that in terms of both incompatible element concentrations and isotopes the rocks are similar to tholeiites from oceanic islands such as Hawaii and Kerguelen, are all factors that reinforce the conclusion that these are mantle derived magmas which have suffered insignificant crustal contamination. They are, however, derived from a mantle which is trace-element enriched relative to the Ambenali source. Thus in the succession as a whole the crustal contribution appears to be small. Maximum amounts of contamination in the Poladpur Formation are difficult to determine but the average amount is probably in the region of 6-12 percentage mass. The whole sequence therefore contains a crustal contribution of about 2-3%.

Saddled Prominent Outbreaks in North America

1988 ◽  
Vol 5 (2) ◽  
pp. 88-91 ◽  
Author(s):  
Peter J. Martinat ◽  
Douglas C. Allen
Keyword(s):  
New York ◽  
North America ◽  
New England ◽  
Sugar Maple ◽  
Eastern North America ◽  
American Beech ◽  
White Mountains ◽  
The Third ◽  
Historical Pattern ◽  
Mountain Systems

Abstract Saddled prominent has caused severe defoliation in eastern North America at 10-13 year intervals since 1907. Outbreaks consisted of simultaneous infestations in physiographically separated New England mountain systems: the Taconic, Berkshire, Green, and White Mountains. In more extensive outbreaks, concurrent infestations occurred within a 2-3 year period in New England, New York, Pennsylvania, Ontario, Quebec, the Canadian Maritimes, Michigan, and Wisconsin. However, outbreaks were most frequent and persistent in New England, where defoliation first appeared on ridges or upper slopes, and American beech and sugar maple composed at least 60% of the forest. In subsequent years, defoliation persisted in these epicenters (outbreak foci) and spread to stands at lower elevations. General population collapse usually occurred during the third or fourth summer following initial defoliation. Based solely on the historical pattern of infestations, outbreaks are predictable if at all, in the Green and White Mountains in New England. North. J. Appl. For. 5:88-91, June 1988.

scholarly journals 40Ar–39Ar ages and isotope geochemistry of Cretaceous basalts in northern Madagascar: refining eruption ages, extent of crustal contamination and parental magmas in a flood basalt province

2012 ◽  
Vol 150 (1) ◽  
pp. 1-17 ◽  
Author(s):  
C. CUCCINIELLO ◽  
L. MELLUSO ◽  
F. JOURDAN ◽  
J. J. MAHONEY ◽  
T. MEISEL ◽  
...  
Keyword(s):  
Isotope Geochemistry ◽  
Crustal Contamination ◽  
Flood Basalt ◽  
Small Range ◽  
Isotopic Compositions ◽  
Wide Range ◽  
Mantle Sources ◽  
Group A ◽  
Group B ◽  
Group D

AbstractThe Madagascar Cretaceous igneous province exposed in the Mahajanga basin is represented by basalt and basaltic andesite lavas. New40Ar–39Ar plateau ages (92.3 ± 2.0 Ma and 91.5 ± 1.3 Ma) indicate that the magmatism in the Mahajanga basin started about 92 Ma ago. Four geochemically distinct magma types (Groups A–D) are present. Group A and C rocks have low to moderate TiO2(1.2–2.6 wt%), Nb (3–9 μg g−1) and Zr (82–200 μg g−1), and show large variations in ɛNdi(+0.1 to −10.8),206Pb/204Pb (15.28 to 16.33) and γOs(+11.4 to +7378). The large isotopic variations, particularly in Os, Nd and Pb isotopic compositions, are likely due to crustal contamination. The low Pb isotope ratios observed in the Group A and C rocks suggest involvement of continental crust with low μ (238U/204Pb). Group B and D rocks have moderate to high TiO2(2.2–4.9 wt%), Nb (8–24 μg g−1) and Zr (120–327 μg g−1). Age-corrected isotopes of Group B and D lavas show a small range in ɛNdi(+1.0 to +4.0) and a wide range in γOs(+128 to +1182). Values of207Pb/204Pb are within the range for Groups A and C, but the Group D206Pb/204Pb (16.52–17.08) and208Pb/204Pb (37.51–38.01) values are higher, indicating a different crustal contaminant. Pb isotopic values of the Group B rocks seem to reflect the isotopic features of their mantle source. The magma groups of Mahajanga display a wide range of trace element and isotopic compositions that cannot be explained only by open-system crystallization processes but, rather, by distinct mantle sources.

The Chengwatana Volcanics, Wisconsin and Minnesota: petrogenesis of the southernmost volcanic rocks exposed in the Midcontinent rift

1997 ◽  
Vol 34 (4) ◽  
pp. 536-548 ◽  
Author(s):  
Karl R. Wirth ◽  
Zachary J. Naiman ◽  
Jeffrey D. Vervoort
Keyword(s):  
Trace Element ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Geothermal Gradient ◽  
Limited Range ◽  
Geochemical Data ◽  
Rift System ◽  
Midcontinent Rift ◽  
Element Abundances ◽  
Isotopic Compositions

The southernmost exposed rocks of the North American Midcontinent rift system (1100 Ma) consist of 3000 m of mafic volcanic flows and minor interflow sediment exposed along the St. Croix River in Minnesota and Wisconsin. The flows are mostly high-Fe tholeiitic basalt with plagioclase phenocrysts and ophitic to subophitic clinopyroxene. Abundant secondary chlorite, epidote, and actinolite indicate the group was metamorphosed to greenschist facies (~350 °C). Low sodium (M4 site) and tetrahedral aluminum (AlIV) contents of actinolite indicate low-pressure metamorphism (0.25 GPa) and imply a geothermal gradient of 45 – 50 °C/km. Low magnesium (Mg# = 0.37–0.58) and Ni contents (36–185 ppm) indicate the basalts have undergone significant fractionation and are not primary mantle melts. Incompatible element abundances are inversely correlated with Mg#, and most samples plot within either high or low trace element groups (e.g., Ti, P, Zr). The basalts are enriched in the light rare earth elements and Th, and are variably depleted in Ta and Nb relative to La and Th. Initial 143Nd/144Nd compositions of the group range from 0.51099 to 0.51122 (initial εNd = −4.5 to +0.1). Most flows have isotopic compositions within a relatively limited range (initial εNd = −2.5 to −1.6), but exhibit variable trace element abundances. Flows with the highest and lowest initial 143Nd/144Nd ratios have isotopic compositions that are inversely correlated with trace element abundances and ratios (e.g., La/Yb, Th/La, Th/Ta). The combined geochemical data suggest that the Chengwatana basalts originated from plume-derived melts and underwent variable fractional crystallization and crustal contamination. These melts may have interacted with lithospheric mantle enriched during Penokean subduction.

Kimberlites as Geochemical Probes of Earth’s Mantle

Elements ◽  
2019 ◽  
Vol 15 (6) ◽  
pp. 387-392 ◽  
Author(s):  
D. Graham Pearson ◽  
Jon Woodhead ◽  
Philip E. Janney
Keyword(s):  
Trace Element ◽  
Transition Zone ◽  
Lithospheric Mantle ◽  
Crustal Contamination ◽  
Incompatible Trace Element ◽  
Magma Source ◽  
Core Mantle Boundary ◽  
The Core ◽  
Earth’S Mantle ◽  
Source Regions

Kimberlites are ultrabasic, Si-undersaturated, low Al, low Na rocks rich in CO2 and H2O. The distinctive geochemical character of kimberlite is strongly influenced by the nature of the local underlying lithospheric mantle. Despite this, incompatible trace element ratios and radiogenic isotope characteristics of kimberlites, filtered for the effects of crustal contamination and alteration, closely resemble rocks derived from the deeper, more primitive, convecting mantle. This suggests that the ultimate magma source is sub-lithospheric. Although the composition of primitive kimberlite melt remains unresolved, kimberlites are likely derived from the convecting mantle, with possible source regions ranging from just below the lithosphere, through the transition zone, to the core–mantle boundary.

A late-glacial transition from Picea glauca to Picea mariana in southern New England

2007 ◽  
Vol 67 (3) ◽  
pp. 502-508 ◽  
Author(s):  
Matts Lindbladh ◽  
W. Wyatt Oswald ◽  
David R. Foster ◽  
Edward K. Faison ◽  
Juzhi Hou ◽  
...  
Keyword(s):  
North America ◽  
New England ◽  
Picea Mariana ◽  
Picea Glauca ◽  
Single Species ◽  
Late Glacial ◽  
Eastern North America ◽  
Southern New England ◽  
Edaphic Conditions ◽  
Ecological Changes

AbstractPicea is an important taxon in late-glacial pollen records from eastern North America, but little is known about which species of Picea were present. We apply a recently developed palynological method for discriminating the three Picea species in eastern North America to three records from New England. Picea glauca was dominant at ∼ 14,500–14,000 cal yr BP, followed by a transition to Picea mariana between ∼ 14,000 and 13,500 cal yr BP. Comparison of the pollen data with hydrogen isotope data shows clearly that this transition began before the beginning of the Younger Dryas Chronozone. The ecological changes of the late-glacial interval were not a simple oscillation in the position of a single species' range, but rather major changes in vegetation structure and composition occurring during an interval of variations in several environmental factors, including climate, edaphic conditions, and atmospheric CO2 levels.

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