Paleomagnetism of Some Leg 33 Sediments and Basalts

Cockerham, Robert S.; Jarrard, Richard D.

doi:10.2973/dsdp.proc.33.121.1976

Cited by 11 publications

(8 citation statements)

References 22 publications

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“…Within each of the three lava types, there are several cooling unit boundaries, but there is no pattern of steep- ening or shallowing of inclinations between these separate flows and the cooling boundaries are not likely to be significant time boundaries. Median demagnetization field values range from 12.7 to 35 mT (127 Oe to 350 Oe), which is in accord with other deep-sea basalts (Cockerham and Jarrard, 1976;Marshall, 1978). Consistent with their lower intensity, the susceptibilities of the Core 595A-10 basalts are less than half the value of those of all other cores in both holes.…”

Section: Basaltssupporting

confidence: 75%

Paleomagnetic Studies of Leg 91 Basalts and Sediments

Montgomery¹,

Johnson²

1987

Initial Reports of the Deep Sea Drilling Project

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Paleomagnetic studies were carried out on 23 basalt and 74 sediment samples from Leg 91 of the Deep Sea Drilling Project, recovered from a portion of the southwestern Pacific plate (24°S, 166°W) dating back to the Early Cretaceous to perhaps Late Jurassic. The expected geocentric axial dipole inclination at this latitude is-41°. The corrected mean stable inclination of-75° for the basalts indicates a paleolatitude of 63 °S for their formation and thus 39° of northward motion during the last 100 m.y. Sediment inclinations steepen rapidly below 13-m depth in the core, suggesting little northward motion of this part of the Pacific plate until about 25 m.y. ago. Examination of the opaque minerals in polished section, as well as the Curie temperatures determined for six basalt samples, reveals no evidence of high-or intermediate-temperature oxidation and thus no reheating of the basement rock since its formation.

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Section: Basaltssupporting

confidence: 75%

Paleomagnetic Studies of Leg 91 Basalts and Sediments

Montgomery¹,

Johnson²

1987

Initial Reports of the Deep Sea Drilling Project

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“…In Pacific plate motion studies, discrepancies between palaeolatitudes determined from sediments and palaeolatitudes determined by other techniques (i.e. basalt remanence, seamount poles, skewness and relative amplitude of marine magnetic anomalies and the age of equatorial sediment facies; Jarrard & Cockerham 1975;Cockerham & Jarrard 1976;Clague & Jarrard 1973;Gordon & Cape 1981) suggest a shallowing of the sediment's magnetic inclination which may be due to burial compaction.…”

Section: Introductionmentioning

confidence: 99%

Compaction-induced inclination shallowing of the post-depositional remanent magnetization in a synthetic sediment

Anson

Kodama

1987

Geophysical Journal International

172

105

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A synthetic sediment comprised of kaolinite, distilled water and either equidimensional or acicular magnetite was given a post-depositional remanent magnetization (PDRM) by being stirred in a magnetic field. This sediment was compacted under pressures which varied continuously from 0 to 0.14 MPa in a water-tank consolidometer and to higher pressure steps (~2 . 5 3 MPa) in a standard soil consolidometer. Compaction took place in the same magnetic field in which the sample was given its PDRM. The compaction caused shallowing of the sample's magnetic inclination.This shallowing was found to be a function of the sample's initial magnetic inclination and the degree of sample compaction;where IR is the remanent inclination after compaction, A V is the volume change, I . is the initial magnetic inclination, and a is an empirically derived constant. The data show a maximum inclination shallowing of 12" for an initial inclination of 54", in good agreement with the maximum inclination shallowing predicted by the above equation.We propose an electrostatic mechanism to be the cause of the inclination shallowing. In this model positively charged magnetite grains adhere to the surface of negatively charged clay grains with their long dimension parallel to the clay grain's surface. As the clay grains become reorientated due to compaction the easy axes of magnetization are rotated away from the axis of compression.Alternating field demagnetization data reveal that our samples have shallower characteristic magnetizations than their post-compaction NRMs, implying that the smaller, higher coercivity grains are most affected by the compaction process. These data support our model since a surface charge mechanism for inclination shallowing would predict that the smallest magnetic grains would be preferentially affected.

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“…The Gorgona Plateau, which is obducted at Gorgona Island (Figure b) and can possibly be related to the secondary volcanism of the Manihiki Plateau [ Pietsch and Uenzelmann‐Neben , ], was accreted to the South American craton in the Paleocene (Figure b) [ Kerr and Tarney , ]. Paleolatitude calculations provide an emplacement latitude between 26°S and 30°S [ Kerr and Tarney , ], which is also the emplacement latitude of the northern Manihiki Plateau [ Cockerham and Jarrard , ; Chandler et al ., ; Hochmuth et al ., ]. The age and petrology correlates to the secondary magmatic phases of the Manihiki Plateau, but it is uncertain whether this magmatic phase occurred on all fragments, although both the Hikurangi Plateau and the Ontong Java Plateau experienced multiple phases of magmatic activity [ Inoue et al ., ; Hoernle et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Collision of Manihiki Plateau fragments to accretional margins of northern Andes and Antarctic Peninsula

Hochmuth

Gohl

2017

Tectonics

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The Manihiki Plateau, a large igneous province (LIP), was emplaced in the Early Cretaceous as a single plateau together with the Ontong Java Plateau and the Hikurangi Plateau. Additional to the present Manihiki Plateau, fragments to its northeast and east have been formed. Plate kinematic reconstructions suggest the capturing of these fragments by the Farallon Plate and the Phoenix Plate, respectively. By tracing these fragments, we report a Paleocene collision of the northeastern Manihiki Plateau fragment with the northern South American craton. The northern Andes exhibit multiple terranes of LIP origin. We infer, based on geophysical, petrological, and geochemical data, that the Piñón formation consists of crustal units of the former Manihiki Plateau. An Early Cretaceous collision of the eastern Manihiki Plateau fragment is reconstructed for West Antarctica. The subduction of this fragment in the Palmer Land region can be associated with the so‐called Palmer Land Event and a flattening of the subduction slab. By reconstructing the dispersal of the fragments of the Manihiki Plateau, we provide a deeper insight in the possible subduction scenarios and buildup of the accretional margins of the northern Andes and the Antarctic Peninsula.

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Paleomagnetism of Some Leg 33 Sediments and Basalts

Cited by 11 publications

References 22 publications

Paleomagnetic Studies of Leg 91 Basalts and Sediments

Paleomagnetic Studies of Leg 91 Basalts and Sediments

Compaction-induced inclination shallowing of the post-depositional remanent magnetization in a synthetic sediment

Collision of Manihiki Plateau fragments to accretional margins of northern Andes and Antarctic Peninsula

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