A Study of Northwestern Mexico

Summary We report 24 palaeomagnetic directions and 10 high-quality Thellier-derived palaeointensity (PI) values, obtained from 27 sites located in Baja California Peninsula, northwestern Mexico. Sampling was done in four rock units (magnesian andesites, calc-alkaline lavas, ignimbrites, adakites) belonging to San Borja and Jaraguay monogenetic volcanic fields. These units have erupted between ∼ 15 and 2.6 Ma (previous K-Ar and 40Ar/39Ar data); hence results are presented in two consecutive periods: middle-late Miocene and Pliocene. The identified main magnetic minerals in the sampled sites are titanomagnetite, magnetite, and minor hematite, of variable grain size, present as intergrowths or surrounding grains, which reflect varying oxidation/reduction conditions during emplacement of high-temperature magmas. Based on previous geological and geophysical records, the kinematic evolution was carefully considered in the region, allowing for the independent restoration of the palaeoposition of each sampled site. Previous palaeodirections were also evaluated and corrected for tectonic motion in order to combine them with present data. Accordingly, a number of 15 and 36 directional data are used to calculate palaeopole position for Pliocene and middle-late Miocene periods, respectively, selected from a total of 74 data points. Pliocene (Plat = 87.8°, Plong = 147.5°, K = 41.06, A95 = 6.0°) and middle-late Miocene (Plat = 86.0°, Plong = 172.7°, K = 41.08, A95 = 3.8) palaeopole positions, calculated after tectonic corrections, are not statistically different from expected North American reference pole. Tectonic correction for Middle-late Miocene virtual geomagnetic poles plays an important role in reducing the resultant tilting from 2.7° to -0.8°. PI mean were calculated for Pliocene and middle-late Miocene periods at 29.2 ± 9.1 μT and 23.2 ± 6.3 μT, respectively. Compiling global filtered PI data, together with our results, indicates that the strength of the geomagnetic field during middle-late Miocene was weak (virtual dipole moment = 5.0 ± 2.2 × 1022 Am2) compared to Pliocene (6.4 ± 2.8 × 1022 Am2), and also relative to the present-day value (7.6 × 1022 Am2). This indicates the global nature of the low dipole moment during the middle-late Miocene period. However, issues related to the spatio-temporal distribution of PI data still present an obstacle to validating these suggestions; therefore, more reliable data are still needed.

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Fuel loads, snag abundance, and snag recruitment in an unmanaged Jeffrey pine–mixed conifer forest in Northwestern Mexico

Forest Ecology and Management ◽

10.1016/j.foreco.2004.04.017 ◽

2004 ◽

Vol 199 (1) ◽

pp. 103-113 ◽

Cited By ~ 52

Author(s):

Scott L. Stephens

Keyword(s):

Conifer Forest ◽

Mixed Conifer ◽

Fuel Loads ◽

Jeffrey Pine ◽

Mixed Conifer Forest ◽

Northwestern Mexico

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The loading history of trace metals and nutrients in Altata-Ensenada del Pabellón, lagoon complex, northwestern Mexico

Journal of Environmental Radioactivity ◽

10.1016/s0265-931x(03)00091-2 ◽

2003 ◽

Vol 69 (1-2) ◽

pp. 129-143 ◽

Cited By ~ 7

Author(s):

A.C. Ruiz-Fernández ◽

F. Páez-Osuna ◽

M. Soto-Jiménez ◽

C. Hillaire-Marcel ◽

B. Ghaleb

Keyword(s):

Trace Metals ◽

Loading History ◽

History Of ◽

Northwestern Mexico

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Molecular Detection of Leishmania (L.) mexicana (Kinetoplastida: Trypanostomatidae) DNA in Culicoides furens (Diptera: Ceratopogonidae) from an Area with Autochthonous Canine Leishmaniasis in Northwestern Mexico

Acta Parasitologica ◽

10.1007/s11686-021-00335-1 ◽

2021 ◽

Author(s):

Juan José Ríos-Tostado ◽

Hipólito Castillo-Ureta ◽

Edith Hilario Torres-Montoya ◽

José Israel Torres-Avendaño ◽

Vicente Olimón-Andalón ◽

...

Keyword(s):

Molecular Detection ◽

Canine Leishmaniasis ◽

Northwestern Mexico

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Biodiversity conservation in the Madrean sky islands: community homogeneity of medium and large mammals in northwestern Mexico

Journal of Mammalogy ◽

10.1093/jmammal/gyx151 ◽

2018 ◽

Vol 99 (2) ◽

pp. 465-477 ◽

Cited By ~ 1

Author(s):

Helí Coronel-Arellano ◽

Nalleli E Lara-Díaz ◽

Claudia E Moreno ◽

Carmina E Gutiérrez-González ◽

Carlos A López-González

Keyword(s):

Biodiversity Conservation ◽

Sky Islands ◽

Large Mammals ◽

Northwestern Mexico ◽

Madrean Sky Islands

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A survey of ecotourism on islands in northwestern México

Environmental Conservation ◽

10.1017/s0376892999000296 ◽

1999 ◽

Vol 26 (3) ◽

pp. 212-217 ◽

Cited By ~ 5

Author(s):

B.R. TERSHY ◽

L. BOURILLÓN ◽

L. METZLER ◽

J. BARNES

Keyword(s):

Government Regulation ◽

Costs And Benefits ◽

Management Options ◽

Western Mexico ◽

Human Use ◽

Northwestern Mexico ◽

Negative Impacts ◽

North Western

The >150 islands in north-western México are relatively pristine, but may easily be damaged by unregulated human use. Tourists visit many of these islands, but their numbers and impact are unknown. To examine some of the costs and benefits of ecotourism we sent a questionnaire to 42 ecotourism companies that visit islands in north-western México; 29 respondents reported that tourist days on these islands had increased at >7% yr-1, from <15 000 in 1986 to about 47 000 in 1993. Neither government regulation nor cost of trips were reported to be important impediments to tourism growth. In 1993, ecotourist organizations visiting islands reported spending US$3.7 million, none of which went directly to the protection and management of the islands. We provide several management options to increase the conservation benefits of ecotourism and minimize the negative impacts.

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