Palaeomagnetic studies of a Cretaceous molasse sequence in the central Andes (Coloso Formation, Northern Chile)

Turner, Peter; Clemmey, H.; Flint, Stephen S.

doi:10.1144/gsjgs.141.5.0869

Cited by 26 publications

(10 citation statements)

References 9 publications

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“…c Recalculated by Beck et al [1994] from Heki et al [1983b], Palmer et al [1980b], and Scanlan and Turner [1992]. d Recalculated by Beck et al [1994] from Hartley et al [1992], Tanaka et al [1988], and Turner et al [1984].…”

Section: Discussionmentioning

confidence: 99%

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New paleomagnetic data from the northern Argentine Puna: Central Andes rotation pattern reanalyzed

Prezzi

Alonso

2002

J.‐Geophys.‐Res.

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Along the central Andes a pattern of vertical axis rotations (CARP) has been paleomagnetically identified. These rotations, which are counterclockwise north of Arica and clockwise to the south, have been detected in Mesozoic and Cenozoic rocks cropping out in the Andean forearc and the Altiplano‐Puna. Different models have been proposed to explain the geodynamic evolution of the central Andes, but the origin of these rotations remains controversial. Such models involve oroclinal bending and/or local block rotations. This lack of agreement is partly due to the scarce paleomagnetic database, particularly for the Argentine Puna. Here we report new paleomagnetic data obtained in the northern Argentine Puna from 57 sites drilled from Miocene volcaniclastic rocks and 12 sites from the Cretaceous‐Eocene Salta Group. It was determined that (1) the Morro Blanco area did not undergo significant vertical axis rotation since at least the middle Miocene; (2) the Loma Blanca mine area underwent a clockwise vertical axis rotation of ∼10° later than the late Miocene; and (3) the Coranzulí area underwent a clockwise vertical axis rotation of ∼40° later than the Cretaceous‐Eocene. The central Andes database was analyzed, and some features of the CARP were determined. These features were explained considering “domino”‐style models for the forearc and a local block rotation model in response to penetrative shear for the Altiplano‐Puna. Penetrative shear would occur along a high electrical conductivity zone. However, the possibility of the existence of an oroclinal bending of <5° cannot be discarded.

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Section: Discussionmentioning

confidence: 99%

“… d Recalculated by Beck et al [1994] from Hartley et al [1992], Tanaka et al [1988], and Turner et al [1984]. …”

Section: Central Andes Paleomagnetic Database and Its Tectonic Signifmentioning

confidence: 99%

New paleomagnetic data from the northern Argentine Puna: Central Andes rotation pattern reanalyzed

Prezzi

Alonso

2002

J.‐Geophys.‐Res.

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“…These authors found indications that rocks of that age in the Frontal Cordillera have been displaced, although given the structural complexity of the region, the paleomagnetic data are difficult to interpret. The available paleomagnetic data for the Mesozoic in Chile indicate that Chilenia was already part of the South American continent by the Cretaceous [Palmer et al, 1980;Turner et al, 1984;May and Butler, 1985].…”

Section: Discussionmentioning

confidence: 99%

Paleozoic terranes of the central Argentine‐Chilean Andes

Ramos¹,

Jordan²,

et al. 1986

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The recognition of accreted terranes and their importance in orogenesis has spurred the search for allochthonous fragments along the western and southern margins of South America. Here we present stratigraphic and petrologic data from Chile and Argentina between 29° and 33°S latitude that demonstrate the “suspect” nature of several major terranes, which we infer to have been accreted during the Paleozoic. Three lower‐middle Paleozoic terranes are described (from east to west): (1) the Pampeanas terrane, a Cambrian‐Devonian magmatic and metamorphic province built on late Precambrian basement at the margin of South America, (2) the Precordillera terrane, a Cambrian‐Devonian shelf‐slope‐oceanic basin assemblage bounded by mélanges on both sides and bearing many stratigraphic similarities to the lower‐middle Paleozoic of the Northern Appalachians, and (3) the “Chilenia” terrane, which has largely been obliterated by late Paleozoic magmatism and metamorphism. The distribution of Carboniferous continental, deltaic, and marine strata demonstrates that these three terranes were sutured together and part of South America by the end of the Devonian. Subsequent Permo‐Carboniferous plate interactions more closely resembled the modern Andean margin, with eastward subduction, accretionary prism formation, and minor terrane emplacement exposed along the present coast of Chile and eastward migrating arc magmatism from the present coast of Chile to western Argentina.

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“…For example, red sandstones which contain detrital magnetite often have a haematite component which is reversed in direction from the lower Tb magnetite component (e.g. Turner, Clemmey & Flint 1984;Robinson & McClelland 1987). This has been used to demonstrate that the reddening took place up to a million years or more after deposition in a later polarity epoch.…”

Section: Introductionmentioning

confidence: 99%

Self Reversal of Chemical Remanent Magnetization On the Transformation of Maghemite to Haematite

McClelland

Goss

1993

Geophysical Journal International

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Self-reversed chemical remanent magnetization (CRM) has been observed in haematite formed on heating maghemite which has been produced by the dehydration of acicular crystals of synthetic lepidocrocite, 1 to 2 p m in length. Our experimental evidence suggests that self reversal of haematite remanence only occurs when the parent maghemite is still blocked at the temperature of its transformation to haematite; when the transformation temperature is above the blocking temperature of the parent maghemite and it is unblocked, the resulting haematite remanence is normally magnetized. It is suggested that the strong dependence on remanent state supports exchange control of the self-reversal process. We propose that the self reversal is probably a general feature of the maghemite to haematite transition, and the significance of the source lepidocrocite in our experiments is that it produces maghemite of a suitable grain size so that much of it remains blocked at the elevated temperatures required to make the transformation to haematite occur over the short time scale of the laboratory experiments. In nature, transformation of maghemite to haematite will occur at much lower temperatures due to the much longer time scales involved, and self reversal of the resulting CRM may occur over a much less restricted grain size range of parent maghemite.

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Palaeomagnetic studies of a Cretaceous molasse sequence in the central Andes (Coloso Formation, Northern Chile)

Cited by 26 publications

References 9 publications

New paleomagnetic data from the northern Argentine Puna: Central Andes rotation pattern reanalyzed

New paleomagnetic data from the northern Argentine Puna: Central Andes rotation pattern reanalyzed

Paleozoic terranes of the central Argentine‐Chilean Andes

Self Reversal of Chemical Remanent Magnetization On the Transformation of Maghemite to Haematite

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