Remagnetization of Cretaceous forearc strata on Santa Margarita and Magdalena Islands, Baja California Sur: Implications for northward transport along the California margin

Hagstrum, Jonathan T.; Sedlock, Richard L.

doi:10.1029/1998tc900009

Cited by 7 publications

(7 citation statements)

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“…Poleward displacement of the paleopoles for the data presented here is small, especially after restoration of the 3° northward displacement of Baja California produced during the Neogene opening of the Gulf of California. We may therefore interpret the TSM paleopole to indicate a much smaller or even absent latitude displacement of Baja California since Cretaceous time than proposed by, e.g., Hagstrum and Filmer [1990] and Hagstrum and Sedlock [1998]. This interpretation resembles that of the San Telmo paleopole, obtained recently from an intrusive complex approximately 150 km to the south [ Böhnel and Delgado‐Argote , 2000], which is concordant with the corresponding 100 Ma reference pole.…”

Section: Interpretations and Discussionsupporting

confidence: 83%

“…Cowan [1994] highlights the uncertainties and conflicts between models based on geologic versus paleomagnetic data. Paleomagnetic studies in the Peninsular Ranges, conducted at many widespread sites on both plutonic and sedimentary rocks, suggest that the Baja peninsula was located ∼1200 km southward of its present position off the southern margin of Mexico between 200 and 50 Ma [e.g., Hagstrum and Filmer , 1990; Lund and Bottjer , 1991; Hagstrum and Sedlock , 1998]. This restoration represents the ∼300 km of separation necessary to close the Neogene Gulf of California plus another ∼900 km of displacement to the south.…”

Section: Introductionmentioning

confidence: 99%

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Discordant paleomagnetic data for middle‐Cretaceous intrusive rocks from northern Baja California: Latitude displacement, tilt, or vertical axis rotation?

2002

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Paleomagnetic results and U/Pb zircon dating from the San Marcos dike swarm and the El Testerazo pluton in the Cretaceous Peninsular Ranges batholith of northern Baja California are used to evaluate alternative pre‐Neogene paleogeographic reconstructions of the Baja California peninsula. The San Marcos dike swarm is a dense, northwest striking, regional dike swarm that is exposed over an ∼100 km long segment of the batholith and has yielded a U/Pb zircon crystallization age of 120 ± 1 Ma. Dike attitudes from the swarm suggest a regionally consistent average ∼320°E strike and ∼79°NE dip. The El Testerazo pluton is a younger tonalite intrusion that truncates the northern end of the dike swarm. All but one of 36 sites sampled in this study show remanence of normal polarity. Paleopoles for the San Marcos dike swarm and El Testerazo pluton are indistinguishable and were combined into a paleopole at 248.1°E, 86.6°N, A95 = 4.8°, which is displaced with respect to the 122 Ma reference pole for stable North America at 198.2°E, 72.3°N, A95 = 3.3°. The displacement may be described by an apparent clockwise rotation of 18° ± 6° and an apparent northward shift of 8° ± 5°. Restoring a northward shift of about 3°, related to the separation of Baja California from North America since 10 Ma, only a marginal northward displacement of 5° ± 5° is left. The clockwise rotation may be the result of crustal block rotations within the right‐lateral shear systems in northern Baja California, although there is no geological evidence that supports this possibility. Alternatively, the difference between paleopole and reference pole may be due to tilting of the study area. Restoring a northeastward tilt of 11°, based on the mean dip measured for the San Marcos dike swarm in the study area, yields a paleopole at 187.6°E, 70.8°N, A95 = 5.6°, which is indistinguishable from the 122 Ma North American reference pole. The tilting hypothesis suggested previously as a potential explanation for low inclination of paleomagnetic data from Baja California therefore seems to be viable for the discordant paleopoles from this segment of the batholith. Data obtained previously about 150 km further south and along the western edge of the batholith defined a concordant paleopole without any tilt correction, indicating that regional tilting may not be valid for all of Baja California.

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Section: Interpretations and Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Discordant paleomagnetic data for middle‐Cretaceous intrusive rocks from northern Baja California: Latitude displacement, tilt, or vertical axis rotation?

2002

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“…, 1984; Kanter & Debiche, 1985; Whidden et al. , 1998), Baja Peninsula (Hagstrum & Filmer, 1990; Hagstrum & Sedlock, 1998) and the Caribbean (Acton et al. , 2000).…”

Section: Pt's Pacific Palaeomagnetic Problemsmentioning

confidence: 99%

Biogeographical and geological evidence for a smaller, completely‐enclosed Pacific Basin in the Late Cretaceous

McCarthy¹

2005

Journal of Biogeography

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Over the last few decades many biogeographical researchers have contended that hundreds of trans-Pacific disjunctions of poor dispersing taxa are more simply explained by removing the plate tectonic assumption of separation by a now-vanished, pre-ABSTRACT Aim To use biogeographical, palaeomagnetic, palaeosedimentary, and plate circuit data from Late Cretaceous regions in and around the Pacific to test the plate tectonic hypothesis of a pre-Pacific superocean.Location East Asia, Australia, Antarctica, the western Americas, and the Pacific.Methods Literature surveys of the distributions of Cretaceous, circum-Pacific taxa were compared with palaeomagnetic and palaeosedimentary data. Uncontroversial plate motions based on seafloor spreading data were also used to test the results of the biogeographical and palaeomagnetic analyses.

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“…In Baja California, the paleomagnetic inclinations of the Cretaceous–early Tertiary rocks are shallower than coeval inclinations from North America. The shallow inclinations have been interpreted to indicate over ∼1000 km of northward terrane displacement of Baja California along the North American craton since the Cretaceous [ Teissere and Beck , 1973; Patterson , 1984; Fry et al , 1985; Hagstrum et al , 1985; Morris et al , 1986; Beck , 1991; Smith and Busby , 1993a; Hagstrum and Sedlock , 1998].…”

Section: Introductionmentioning

confidence: 99%

“…A posttilting remagnetization could cause anomalously shallow paleomagnetic inclinations in stratigraphic coordinates. At least two episodes of remagnetization during Late Cretaceous and Tertiary time have been recognized from a number of formations in Baja California [ Hagstrum et al , 1985; Kamerling and Luyendyk , 1985; Hagstrum and Filmer , 1990; Hagstrum and Murchey , 1993] and these remagnetization events were probably widespread in Baja California [ Hagstrum and Sedlock , 1998].…”

Section: Introductionmentioning

confidence: 99%

New paleomagnetic, rock magnetic, and petrographic results from the Valle Group, Baja California, Mexico: Exploring the causes of anomalously shallow paleomagnetic inclinations

Kodama

Smith

2004

J. Geophys. Res.

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[1] A detailed paleomagnetic, rock magnetic, and sedimentologic study was conducted on Cenomanian-age strata of the Valle Group at El Campito, Baja California, to examine the burial compaction effects on the paleomagnetic inclination of marine sedimentary rocks. Alternating field and thermal demagnetization isolated a characteristic remanence at 16 of 18 sites with a mean of Dec = 342.6°, Inc = 19.1°, and a 95 = 3.4°. The inclination is 38.7°shallower than that predicted by the reference paleopole for North America. Laboratory experiments indicate that compaction could account for only 7.5°of the inclination shallowing. Fold tests at different scales yield both positive and negative results, making a tight constraint on the remanence's age impossible. A primary postdepositional remanence is supported by bedding-parallel foliations in the anisotropy of anhysteretic remanence fabric. Although primary anomalously shallow inclinations could indicate significant southerly, then northerly, paleolatitudinal offset, a more likely scenario is a late Cenozoic low-temperature remagnetization, which is suggested by alteration along the edges of some detrital silicate grains and a bimodal magnetic grain size distribution revealed by isothermal remanence data. The synthesis of the data indicates that the Vizcaino terrane was contiguous with the Cordillera margin during remagnetization and underwent a subsequent 13.5 ± 5.4°clockwise rotation. We tentatively interpret that the remagnetization resulted from burial and/or Miocene volcanism, which caused an acquisition of thermochemical remanent magnetization (TCRM). This study reveals a complicated remanence that resists easy interpretation and suggests caution in studies of similar rocks.

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Remagnetization of Cretaceous forearc strata on Santa Margarita and Magdalena Islands, Baja California Sur: Implications for northward transport along the California margin

Abstract: Abstract. Paleomagnetic data for two sections of Cretaceous

Cited by 7 publications

References 58 publications

Discordant paleomagnetic data for middle‐Cretaceous intrusive rocks from northern Baja California: Latitude displacement, tilt, or vertical axis rotation?

Discordant paleomagnetic data for middle‐Cretaceous intrusive rocks from northern Baja California: Latitude displacement, tilt, or vertical axis rotation?

Biogeographical and geological evidence for a smaller, completely‐enclosed Pacific Basin in the Late Cretaceous

New paleomagnetic, rock magnetic, and petrographic results from the Valle Group, Baja California, Mexico: Exploring the causes of anomalously shallow paleomagnetic inclinations

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