scholarly journals Influence of inclination error in sedimentary rocks on the Triassic and Jurassic apparent pole wander path for North America and implications for Cordilleran tectonics

2010 ◽  
Vol 115 (B10) ◽  
Author(s):  
Dennis V. Kent ◽  
Edward Irving
Keyword(s):  
North America ◽  
Sedimentary Rocks ◽  
Cordilleran Tectonics

Extent of Grenvillian remanence components in rocks of the Southern Province

1982 ◽  
Vol 19 (4) ◽  
pp. 698-708 ◽  
Author(s):  
M. Stupavsky ◽  
D. T. A. Symons
Keyword(s):  
Magnetic Field ◽  
North America ◽  
Thin Section ◽  
Sedimentary Rocks ◽  
Pole Position ◽  
River Valley ◽  
Field Reversal ◽  
Paleomagnetic Study ◽  
Northern Portion ◽  
Sediment Matrix

Early Aphebian Gowganda sedimentary rocks and intruding Nipissing diabase sills were sampled for paleomagnetic study at 88 sites (~500 cores, ~1000 specimens) along two ~42 km long profiles extending north from the Grenville Front into the Cobalt Plate of the Southern Structural Province in the River Valley – Lake Temagami area of Ontario. After AF demagnetization a postfolding pre-Nipissing ~2200 Ma remanence was found in eight of the 37 Gowganda sediment sites that were > 2 km north of the front, giving a pole at 109°W, 63°N (dp = 10°, dm = 19°). The Nippissing diabase from > 2 km north of the front retains a stable antiparallel prefolding N1 remanence direction in 22 of 40 sites, giving a pole position of 85°W, 17°S (dp = 6°, dm = 10°). These "south and down" remanence directions found in the southern portion of the plate contrast with the antiparallel "north and up" directions found in the northern portion, thereby indicating the occurrence of either two nearly cogenetic Nipissing intrusive events or the sequential emplacement of the Nipissing during an Earth's magnetic field reversal across the plate. At two sites a Nipissing remagnetized remanence was found in Gowganda sediments with a pole of 115°W, 18°S. Also three "Nipissing" sites give a pole at 164°W, 3°N, which is close to the known pole for the later ~1.25 Ga Sudbury olivine diabase dikes. One site is adjacent to a large dike and two were found on thin-section examination to be olivine diabase. The eight sites in Gowganda sediment matrix and conglomerate clasts and in Nipissing diabase from within < 2 km from the front were found to have a postfolding metamorphic remanence with a Grenville orogenic pole at 45°W, 51°N (dp = 19°, dm = 21°). Finally, the results lead to a suggested revision in the APW path for the ~2300–~1650 Ma interval for North America.

Precambrian-Cambrian Boundary: the spike is driven and the monolith crumbles

Paleobiology ◽  
1983 ◽  
Vol 9 (3) ◽  
pp. 199-206 ◽  
Author(s):  
J. John Sepkoski ◽  
Andrew H. Knoll
Keyword(s):  
Nineteenth Century ◽  
North America ◽  
Sedimentary Rocks ◽  
Historical Record ◽  
Early Cambrian ◽  
Valid Argument ◽  
Sixth Edition ◽  
Rock Record ◽  
Sudden Appearance ◽  
Invertebrate Assemblages

The Precambrian-Cambrian Boundary traditionally has been viewed as a fundamental discontinuity in the historical record of life. Almost from the birth of stratigraphic geology, it was recognized that the richly fossiliferous strata of Cambrian and younger periods were underlain by sedimentary rocks largely devoid of macroscopic fossils. Darwin (1872) was well aware of this dichotomy and of the “sudden manner in which several groups of species first appear” in the rock record. In the sixth edition of theOrigin of Species(1872), he wrote, “The case [for this sudden appearance] at present must remain inexplicable … and may be truly urged as a valid argument against the views [on evolution] here entertained.” Careful biostratigraphic work by Walcott and others in the closing decades of the nineteenth century accentuated rather than dispelled the problem. Diverse Early Cambrian invertebrate assemblages were documented from North America and Scandinavia, but repeated searches for comparable fossils in Precambrian strata produced only a few, enigmatic remains (see review by Yochelson [1979]).

Structural Succession, Nomenclature, and Interpretation of Transported Rocks in Western Newfoundland

1975 ◽  
Vol 12 (11) ◽  
pp. 1874-1894 ◽  
Author(s):  
Harold Williams
Keyword(s):  
North America ◽  
Subduction Zone ◽  
Continental Margin ◽  
North American ◽  
Sedimentary Rocks ◽  
Eastern North America ◽  
Stacking Order ◽  
Ophiolite Suite ◽  
Plutonic Rocks

The Humber Arm and Hare Bay Allochthons of Western Newfoundland are made up of a variety of sedimentary rocks and volcanic and plutonic rocks that originated toward the east and record the evolution and destruction of the ancient continental margin of Eastern North America. Five contrasting rock assemblages that constitute different structural slices are defined and delineated in the Humber Arm Allochthon. Six contrasting rock assemblages constitute the Hare Bay Allochthon. In each allochthon, the lower structural slices consist of sedimentary rocks and the highest structural slice consists of the ophiolite suite. The stacking order and mode of assembly indicate that progressively higher slices travelled increasingly greater distances, so that their present vertical superposition represents a former west-to-east juxtaposition.Most of the transported rocks have direct lithic correlatives in central Newfoundland. These occur west of the Dunnage Mélange, so that if the Dunnage marks the vestige of a North American subduction zone, then all the transported sequences once lay between a continental margin and a nearby oceanic trench.

An Outline of Chinese Geology

1921 ◽  
Vol 58 (7) ◽  
pp. 324-329
Author(s):  
J. S. Lee
Keyword(s):  
North America ◽  
Sedimentary Rocks ◽  
Coarse Grained ◽  
High Mountains ◽  
Crystalline Limestone ◽  
Gneiss Granite ◽  
Wutai Shan ◽  
Southern Flank ◽  
Chlorite Schist

When Richthofen journeyed in the Wutai district, Shan-si, he found a mighty sequence of metamorphosed sedimentary strata which could not be classed as his Sinian or any series younger than the Sinian, nor could it be regarded as belonging to the Old Gneiss and Gneiss-granite group. They are apparently equivalent to similar strata occurring in eastern Shan-tung and Liao-tung. In descending the Wutai-shan along its southern flank, Richthofen first came across a thick series of green schists with alternating beds of grey slates and quartzites, and then several series of coarse quartzitic and felspathic well-stratified rocks, aggregating to a thickness of more than 5,900 feet. He calls the whole sequence of these strata the “Wutai Formation”, and parallels it with the Huronian. This term at once found a wide application in Chinese geology. Thus in the western Tsing-ling Range, south of Lioyang-hsien (about long. 106° E., lat. 33° 25′ N.), and in the high mountains west of Ta-tsien-lu (about long. 102° 10′ E., lat. 30° N.), Loczy distinguishes a series of highly metamorphosed sedimentary rocks, such as gneiss, schists, phyllites, crystalline limestone, etc., and assigns it to the Wutai Formation. The “Nan-shan Sandstone”a series of unfossiliferous grey and green sandstones with well-cleaved or even schistose clayslates, typically developed in the northern foothills of the Nan-shan Ranges—is also tentatively regarded by the same author as a Wutai Formation. Between Ping-liang and Men-chou, in the province of Kan-su, Futterer identified in several places the Nan-shan Sandstone, and found other metamorphosed sedimentary strata of the Wutai Formation, consisting of chlorite-schist, coarse-grained quartzite, slate, and graywacke. In all these cases the term Wutai evidently implies the analogy with the Algonkian of North America.

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