A new method to determine paleosecular variation

Vandamme, Didier

doi:10.1016/0031-9201(94)90012-4

Cited by 260 publications

(354 citation statements)

References 15 publications

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“…All the other latitude bands were much more poorly fit by a Fisher distribution, largely because they had too many low latitude poles (see Table 1, column 4). [10] In order to arrive at a better fit for the latitudinal variation of VGPs, I decided to try a distribution suggested by myself [Harrison, 1980] and by Kristjansson and McDougall [1982] and Vandamme [1994] of having a Fisher distribution plus a ''uniform'' distribution. The uniform distribution that I tried was either one in which the VGPs had a uniform probability as a function of latitude (model 1) or one in which the VGPs had a uniform probability as a function of area (model 2), which produces relatively more poles at low latitudes than at high latitudes.…”

Section: Resultsmentioning

confidence: 99%

“…Because the scatter of poles increases at higher observation latitudes, use of a constant cutoff latitude means that a higher percentage of data is removed from high-latitude observations than from low-latitude observations. Vandamme [1994] proposed a method that would mostly allow for this, by defining the cutoff colatitude as a function of the ASD, noting that a 40°cutoff angle is too large to estimate low values of ASD but too small to estimate high values of ASD. His equation is given below.…”

Section: Introductionmentioning

confidence: 99%

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Latitudinal signature of Earth's magnetic field variation over the last 5 million years

Harrison

2009

Geochem Geophys Geosyst

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[1] In order to investigate the latitudinal effect of the geomagnetic field variation, a new data set consisting of virtual geomagnetic poles (VGPs) from all latitudes has been produced. Since the updated data set was limited to data with VGPs within 45°of the geographic poles, data from lava flows with low-latitude VGPs were added. More rigorous criteria were used to winnow the data. The data were divided into groups from different observation latitudes. In each group it was shown that the distribution of VGP latitudes could be described by a predominance of poles (average 82%) following a Fisher distribution with the rest following a distribution that would produce a uniform number of poles as a function of latitude. A distribution composed of two Fisher distributions also fit the data very well. For the case using a Fisher distribution plus a uniform distribution, the Fisher distribution changed such that the angular standard deviation (ASD) of VGPs from a set of observations taken at the equator is about 10°and the ASD at 60°observation latitude is about 19°. These results are similar to some results seeking to determine the ASD of VGPs as a function of observation latitude using other methods, which have been recently published, but there are also discrepancies. The results allow us to model inclination distributions as a function of observation latitude for comparison with data in which only the inclination is known, such as data from drill holes. It is shown that in order not to have doubt about the polarity of the inclination data, a drill hole has to be located at an absolute latitude greater than 27°for there to be less than a 5% error. This has major importance for the location of the ''Mission to the MOHO'' of the Integrated Ocean Drilling Program. The results also confirm that the sources of the nondipole field located in the outer core have to be more than twice as strong at high latitudes than at low latitudes so as to produce the observed increase in VGP scatter with observation latitude. The model of the secular variation proposed here is in no way a theory about how the secular variation happens, but it does allow those who wish to develop such a theory to have a model distribution with which to check their predictions.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Latitudinal signature of Earth's magnetic field variation over the last 5 million years

Harrison

2009

Geochem Geophys Geosyst

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“…[2] Cenozoic extension and exhumation have led to exposure of previously subducted and metamorphosed portions of the Aegean and west Anatolian mountain belts, which have inspired geological reconstructions of the orogen's root over the past decades [e.g., Schuiling, 1962;Andriessen et al, 1979;Bonneau and Kienast, 1982;van der Maar and Jansen, 1983;Lister et al, 1984;Schermer, 1990;Jolivet et al, 1994aJolivet et al, , 2004Lips et al, 1998;Gautier et al, 1999;Bozkurt, 2001b;Mposkos and Kostopoulos, 2001;Brun and Sokoutis, 2007;Jolivet and Brun, 2010]. The database from both the metamorphic and nonmetamorphic domains of the Aegean and west Anatolian orogen is among the richest in the world, making the region instrumental to geologically calibrate geodynamic processes, linking, e.g., back-arc extension and exhumation to slab roll-back [Berckhemer, 1977;Le Pichon and Angelier, 1979;Meulenkamp et al, 1988;Jolivet and Faccenna, 2000;Jolivet, 2001], nappe stacking to subduction [Faccenna et al, 2003;van Hinsbergen et al, 2005avan Hinsbergen et al, , 2005cJolivet and Brun, 2010], exhumation of (ultra-) highpressure ((U)HP) metamorphic rocks to subduction channel 1 [Thomson et al, 1999;Jolivet et al, 2003;Ring et al, 2007Ring et al, , 2010 or back-arc evolution [Avigad et al, 1997;Ring and Layer, 2003], and dating and calibrating tectonic and volcanic responses to slab edge tectonics [Govers and Wortel, 2005;van Hinsbergen et al, 2007;Zachariasse et al, 2008;…”

Section: Introductionmentioning

confidence: 99%

“…The database from both the metamorphic and nonmetamorphic domains of the Aegean and west Anatolian orogen is among the richest in the world, making the region instrumental to geologically calibrate geodynamic processes, linking, e.g., back-arc extension and exhumation to slab roll-back [Berckhemer, 1977;Le Pichon and Angelier, 1979;Meulenkamp et al, 1988;Jolivet and Faccenna, 2000;Jolivet, 2001], nappe stacking to subduction [Faccenna et al, 2003;van Hinsbergen et al, 2005avan Hinsbergen et al, , 2005cJolivet and Brun, 2010], exhumation of (ultra-) highpressure ((U)HP) metamorphic rocks to subduction channel 1 [Thomson et al, 1999;Jolivet et al, 2003;Ring et al, 2007Ring et al, , 2010 or back-arc evolution [Avigad et al, 1997;Ring and Layer, 2003], and dating and calibrating tectonic and volcanic responses to slab edge tectonics [Govers and Wortel, 2005;van Hinsbergen et al, 2007;Zachariasse et al, 2008;Dilek and Altunkaynak, 2009].…”

Section: Introductionmentioning

confidence: 99%

“…Arrows represent a selection of the most important reported paleomagnetic declinations with respect to south, giving the outline of the Aegean orocline, which runs from northern Albania to the Isparta Angle. White arrows represent directions measured in lower Miocene and older rocks, and gray arrows represent late Miocene and younger directions: 1, Apulian platform, no or little rotation since Eocene [Tozzi et al, 1988;Scheepers, 1992;Speranza and Kissel, 1993]; 2, Dinarids, no rotation since the Cretaceous ; 3, Albania, ∼50°of rotation since the early Miocene [Speranza et al, 1992Mauritsch et al, 1995Mauritsch et al, , 1996; 4, western Greece and Peloponnesus, ∼50°c lockwise rotation since the early Miocene Freeman, 1982, 1983;Kissel et al, 1984Kissel et al, , 1985Kissel and Laj, 1988;Márton et al, 1990;Morris, 1995;van Hinsbergen et al, 2005b]; 5, Moesian platform and Rhodope, no significant post-Eocene rotation with respect to the Eurasian APWP ; 6, Lesbos, no significant rotation of Miocene volcanics [Kissel et al, 1989;Beck et al, 2001]; 7, Crete, local, variable, strike-slip-related post-Messinian counterclockwise rotations [Duermeijer et al, 1998]; 8, Rhodos, Pleistocene counterclockwise rotation, without rotation between early Miocene and Pleistocene [Laj et al, 1982;van Hinsbergen et al, 2007]; 9, Bey Dağları, ∼20°counterclockwise rotations [Kissel and Poisson, 1987;Morris and Robertson, 1993;van Hinsbergen et al, 2010]; 10, Isparta Angle, no Pliocene or younger rotations in its center [Kissel and Poisson, 1986]; 11, clockwise rotations between the Eocene and Miocene of the eastern limb of the Isparta Angle, delimiting the eastern edge of the Aegean orocline ; 12, post-early Miocene clockwise rotation of the volcanic fields of Afyon [Gürsoy et al, 2003]. VAN …”

Section: Introductionmentioning

confidence: 99%

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Exhumation with a twist: Paleomagnetic constraints on the evolution of the Menderes metamorphic core complex, western Turkey

et al. 2010

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Much remains to be understood about the links between regional vertical axis rotations, continental extension, and shortening. In western Turkey, Miocene vertical axis rotations have been reported that occur simultaneously with the extensional exhumation of the Menderes metamorphic core complex, which has been related to back‐arc extension in the eastern part of the Aegean back arc. In this paper we explore the spatial and temporal relationships between vertical axis rotations in southwestern Turkey and extensional unroofing of the Menderes Massif. To this end, we provide a large set of new paleomagnetic data from western Turkey, and integrate these with the regional structural evolution to test the causes and consequences of oroclinal bending in the Aegean region. The Lycian Nappes and Bey Dağları are shown to rotate ∼20° between 16 and 5 Ma, defining the eastern limb of the Aegean orocline. This occurred contemporaneously with the exhumation of the central Menderes Massif (along extensional detachments) and after the latest Oligocene to early Miocene exhumation of the northern and southern Menderes massifs. Exhumation of the latter two was not associated with vertical axis rotations. The lower Miocene volcanics in the region from Lesbos to Uşak, to the north of the central Menderes Massif underwent a small clockwise rotation, insignificant with respect to Eurasia. This shows that exhumation of the central Menderes Massif was associated with a vertical axis rotation difference between the northern and southern Menderes massifs of ∼25°–30°. This result is in excellent agreement with the angle defined by the trends of Büyük Menderes and Alaşehir detachments, as well as the angle defined by the regionally curving stretching lineation pattern across the central Menderes Massif. These structures define a pivot point (rotation pole) for the west Anatolian rotations. The rotation of the southern domain, including the southern Menderes Massif, the Lycian Nappes, and Bey Dağları, must have led to N–S contraction east of this pole. The eastern limit of the rotating domain is formed by the transpressional couple of the Aksu thrust and Kırkkavak Fault in the center of the Isparta angle. Previously reported clockwise rotations in the volcanic fields near Afyon may be the result of distributed N–S shortening east of the pivot point. The precise accommodation of this shortening history remains open for investigation. Late Oligocene to early Miocene extension in the eastern part of the Aegean back arc was NE–SW oriented and likely bounded by a discrete transform. This transform may be associated with an early evolution of the eastern Aegean subduction transform edge propagator fault. Oroclinal bending in the west Anatolian region is likely related to a reconnection of the eastern part of the Aegean orocline with the African northward moving plate in tandem with roll back in the Aegean back arc, comparable to a recently postulated scenario for western Greece.

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Untangling inconsistent magnetic polarity records through an integrated rock magnetic analysis: A case study on Neogene sections in East Timor

Aben

Dekkers

Bakker

et al. 2014

Geochem Geophys Geosyst

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Inconsistent polarity patterns in sediments are a common problem in magnetostratigraphic and paleomagnetic research. Multiple magnetic mineral generations result in such remanence ''haystacks.'' Here we test whether end-member modeling of isothermal remanent magnetization acquisition curves as a basis for an integrated rock magnetic and microscopic analysis is capable of isolating original magnetic polarity patterns. Uppermost Miocene-Pliocene deep-marine siliciclastics and limestones in East Timor, originally sampled to constrain the uplift history of the young Timor orogeny, serve as case study. An apparently straightforward polarity record was obtained that, however, proved impossible to reconcile with the associated biostratigraphy. Our analysis distinguished two magnetic endmembers for each section, which result from various greigite suites and a detrital magnetite suite. The latter yields largely viscous remanence signals and is deemed unsuited. The greigite suites are late diagenetic in the Cailaco River section and early diagenetic, thus reliable, in the Viqueque Type section. By selecting reliable sample levels based on a quality index, a revised polarity pattern of the latter section is obtained: consistent with the biostratigraphy and unequivocally correlatable to the Geomagnetic Polarity Time Scale. Although the Cailaco River section lacks a reliable magnetostratigraphy, it does record a significant postremagnetization tectonic rotation. Our results shows that the application of well-designed rock magnetic research, based on the end-member model and integrated with microscopy and paleomagnetic data, can unravel complex and seemingly inconsistent polarity patterns. We recommend this approach to assess the veracity of the polarity of strata with complex magnetic mineralogy.

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A new method to determine paleosecular variation

Cited by 260 publications

References 15 publications

Latitudinal signature of Earth's magnetic field variation over the last 5 million years

Latitudinal signature of Earth's magnetic field variation over the last 5 million years

Exhumation with a twist: Paleomagnetic constraints on the evolution of the Menderes metamorphic core complex, western Turkey

Untangling inconsistent magnetic polarity records through an integrated rock magnetic analysis: A case study on Neogene sections in East Timor

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