scholarly journals Magnetic susceptibility of Middle Ordovician sedimentary rocks, Pakri Peninsula, NW Estonia

2016 ◽  
Vol 65 (3) ◽  
pp. 125 ◽  
Author(s):  
J Plado ◽  
L Ainsaar ◽  
M Dmitrijeva ◽  
K Põldsaar ◽  
S Ots ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Sedimentary Rocks ◽  
Middle Ordovician

scholarly journals Testing the Reliability of Sedimentary Paleomagnetic Datasets for Paleogeographic Reconstructions

2020 ◽  
Vol 8 ◽  
Author(s):  
Edoardo Dallanave ◽  
Uwe Kirscher
Keyword(s):  
Magnetic Susceptibility ◽  
Spatial Distribution ◽  
New Caledonia ◽  
Sedimentary Rocks ◽  
Paleomagnetic Data ◽  
Polar Wander ◽  
Distribution Shape ◽  
Measurement And Analysis ◽  
Temporal Continuity ◽  
Strain Data

Paleogeographic reconstructions largely rely on paleomagnetic data, mostly in the form of paleomagnetic poles. Compilations of poles are used to determine so called apparent polar wander paths (APWPs), which capture the motion through time of a particular location with respect to an absolute reference frame such as the Earth’s spin axis. Paleomagnetic datasets from sedimentary rocks are particularly relevant, because of their spatial distribution and temporal continuity. Several criteria have been proposed through the years to assess the reliability of paleomagnetic datasets. Among these, the latitudinal-dependent elongation of a given paleomagnetic directions distribution, predicted by a widely accepted paleosecular variations model, has been applied so far only to investigate inclination flattening commonly observed in sedimentary rocks. We show in this work that this concept can be generalized to detect “contamination” of paleomagnetic data derived from tectonic strain, which is not always detected by field observation only. After generating different sets of simulated geomagnetic directions at different latitudes, we monitored the variations in the shape of the distributions after applying deformation tensors that replicate the effect of increasing tectonic strain. We show that, in most cases, the “deformation” of the dataset can be detected by elongation vs. inclination ratios not conforming to the values predicted by the paleosecular variations model. Recently acquired paleomagnetic directions and anisotropy of magnetic susceptibility (AMS; a parameter very sensitive to tectonic strain) data from New Caledonia verifies the results of these simulations and highlights the importance of measuring AMS when using sedimentary paleomagnetic data for paleogeographic reconstruction. We suggest to include always AMS measurement and analysis of the distribution shape to assess sedimentary paleomagnetic data used for paleogeographic reconstructions.

scholarly journals Application of magnetic susceptibility as a paleoclimatic proxy on Paleozoic sedimentary rocks and characterization of the magnetic signal – IGCP-580 projects and events

Episodes ◽  
2014 ◽  
Vol 37 (2) ◽  
pp. 87-95 ◽  
Author(s):  
Anne-Christine Da Silva ◽  
Michael T. Whalen ◽  
Jindrich Hladil ◽  
Leona Koptikova ◽  
Daizhao Chen ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Sedimentary Rocks ◽  
Magnetic Signal ◽  
Paleoclimatic Proxy

Provenance of Paleozoic sedimentary rocks in the Canadian Cordilleran miogeocline: a Nd isotopic study

1997 ◽  
Vol 34 (12) ◽  
pp. 1603-1618 ◽  
Author(s):  
Carmala N. Garzione ◽  
P. Jonathan Patchett ◽  
Gerald M. Ross ◽  
JoAnne Nelson
Keyword(s):  
British Columbia ◽  
Northwest Territories ◽  
Middle Devonian ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Canadian Shield ◽  
Isotopic Study ◽  
Middle Ordovician ◽  
Southern Alberta ◽  
T Values

Nd isotopes and trace elements in sedimentary rocks of the Yukon, the Northwest Territories, and northern British Columbia are used to examine the source of sediments in the Canadian Cordilleran miogeocline. Previous Nd isotope studies in southern Alberta demonstrated that strata of Neoproterozoic to Late Ordovician age were derived from Archean and Proterozoic Canadian Shield sources, whereas by the Late Devonian, a shift of 6 εNd units to younger crustal sources (εNd (T) = −6 to −9) had occurred. In this study, we found that the shift to younger crustal Nd isotopic signatures in the Yukon and Northwest Territories occurred much earlier than in southern Alberta. Cambrian and older strata have εNd(T) values of −10.0 to −21.1, consistent with derivation from Canadian Shield sources. Lower Ordovician through Permian strata in the Yukon and Northwest Territories, including the Innuitian-derived Imperial Assemblage, have εNd(T) values of −5 to −11.4. In northern British Columbia, the shift to a younger source reflects a wider range of εNd(T) values, from -−8.7 to −14.6 in Middle Ordovician through Middle Devonian strata, suggesting continued input from Canadian Shield sources. By the Middle Devonian, a complete shift to younger crustal signatures (εNd(T) = −5.9 to −10.5) had occurred in northern British Columbia. Several sources for the more juvenile sediments include (1) a mixture of locally erupted volcanic rocks with Canadian Shield sources, (2) a Grenville source, and (3) an Innuitian source. We propose that Ordovician to Lower Devonian strata were derived from a mixture of locally erupted, juvenile volcanics and pre-Cambrian Canadian Shield sources, and post-Middle Devonian strata were sourced from the Innuitian orogen in the Canadian Arctic.

The Ordovician volcanics of the Elmtree–Belledune inlier and their relationship to volcanics of the northern Miramichi Highlands, New Brunswick

1992 ◽  
Vol 29 (7) ◽  
pp. 1430-1447 ◽  
Author(s):  
J. A. Winchester ◽  
C. R. van Staal ◽  
J. P. Langton
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Late Ordovician ◽  
Igneous Rocks ◽  
Volcanic Arc ◽  
Middle Ordovician ◽  
Marginal Basin ◽  
Tectonic Mélange ◽  
Back Arc

An investigation of the geology and chemistry of the basic igneous rocks in the Elmtree and Belledune inliers in northern New Brunswick shows that the bulk of the Middle Ordovician rocks of the ophiolitic Fournier Group are best interpreted as the products of volcanism and sedimentation in an extensive ensimatic back-arc basin southeast of a volcanic arc. The oceanic back-arc-basin igneous rocks form the basement to renewed arc-related basaltic volcanism in late Middle to Late Ordovician time. The Fournier Group is separated from the structurally-underlying, shale-dominated Elmtree Formation of the Tetagouche Group by an extensive tectonic melange, which incorporates lenses of serpentinite, mafic volcanic rocks, and sedimentary rocks of both the Tetagouche and Fournier groups. The mafic volcanic rocks in the Elmtree Formation correlate best with those intercalated with the lithologically similar sediments of the Llandeilian–Caradocian Boucher Brook Formation in the northern Miramichi Highlands. The melange and the present structural amalgamation of the Tetagouche and Fournier groups result from closure of the marginal basin by northward-directed subduction at the end of the Ordovician. Most mafic suites in the Elmtree and Belledune inliers can be chemically correlated with similar suites in the northern Miramichi Highlands, showing that the two areas are not separated by a terrane boundary.

The Taconian orogeny in southern New England: Nd-isotope evidence against addition of juvenile components

1996 ◽  
Vol 33 (12) ◽  
pp. 1612-1627 ◽  
Author(s):  
B. Bock ◽  
S. M. McLennan ◽  
G. N. Hanson
Keyword(s):  
New England ◽  
Sedimentary Rocks ◽  
Late Ordovician ◽  
Nd Isotope ◽  
Middle Ordovician ◽  
Southern New England ◽  
Isotope Evidence ◽  
Juvenile Crust ◽  
Plutonic Rocks ◽  
Laurentian Margin

Nd-isotope data for pre-Taconian (meta)sedimentary and igneous rocks, syn-Taconian (meta)sedimentary rocks, and Late Ordovician–Silurian plutonic rocks indicate that the Ordovician Taconian orogeny did not add significant amounts of juvenile crust to the Laurentian margin in southern New England. Nd-isotope compositions of Grenvillian crust and Late Proterozoic to Early Cambrian rift sediments range from εNd of −3.1 to −6.6 at 450 Ma. Sedimentary rocks deposited during the Cambrian and the early Middle Ordovician, which represent the drift stage of Laurentia, and earliest Taconian sedimentary rocks show more negative εNd(450 Ma), with a range from −11.7 to −13.3. Sedimentary rocks deposited in response to the Taconian orogeny have uniform εNd(450 Ma) values of about −8. Middle to Late Ordovician and Permian plutonic rocks from southwestern Connecticut have εNd(450 Ma) values of −2 to −5, which indicates that these rocks contain older crustal components. Rocks with juvenile Nd characteristics are the early Paleozoic Maltby Lake Volcanics (εNd(450 Ma) +8) from southwestern Connecticut, and Middle Ordovician igneous samples from the Hawley Formation (εNd(450 Ma) +6 to −0.6) in Massachusetts.

scholarly journals Sources of paleomagnetic signal in iron-bearing marine sedimentary deposits

2019 ◽  
Vol 486 (1) ◽  
pp. 53-56
Author(s):  
M. A. Rudmin ◽  
A. K. Mazurov ◽  
V. I. Sergienko ◽  
O. G. Savichev ◽  
I. P. Semiletov
Keyword(s):  
Magnetic Susceptibility ◽  
Bottom Sediments ◽  
Methane Emission ◽  
Western Siberia ◽  
Sedimentary Rocks ◽  
Magnetic Signal ◽  
Sedimentary Deposits ◽  
Two Factors ◽  
Iron Bearing

This paper presents the results of interpreting the change in the magnetic signal of ferruginous marine sedimentary rocks using the example of the Cretaceous-Paleogene Bakchar deposit (Western Siberia). Anomalous magnetic susceptibility (MS) values are determined by two factors: (a) a diagenetic process accompanied by the formation of pyrrhotite, greigite and siderite in ironstones, (b) an increase detrital input with deposition of magnetite and ilmenite in the siltstones on the background of climate moistening and intense weathering. It is shown that increased MS values in iron-bearing marine sedimentary deposits can be associated with the formation of ferrimagnetic sulfides, which indicates to the methane emission through ancient marine bottom sediments.

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