Abstract
New paleomagnetic data from southern Mexico provide a magnetostratigraphic framework to correlate mammal‐bearing continental sections of the Suchilquitongo Formation to the Early Miocene part of the geomagnetic polarity time scale. A total of 127 paleomagnetic samples were collected from 40 horizons belonging to two sections. The sequence is characterized by a succession of cream to light pink to gray, thin‐ to medium‐bedded tuffaceous sandstones and siltstones, partly silicified limestones, and a dominantly light green ignimbrite deposited in a fluviolacustrine environment. Remanent magnetization generally has been characterized by two components, a present‐day field component with low‐unblocking temperatures up to 350°C and a characteristic component with unblocking temperatures up to 580°–610°C. The characteristic component is interpreted as primarily based on antipodal populations of remanence data. Six sites at the top of the section ($$\mathrm{inclination}\,=40.5^{\circ }$$ , $$\mathrm{declination}\,=11.3^{\circ }$$ , $$\alpha _{95}=1.4$$ , and $$K=471$$ ) have a mean paleomagnetic direction rotated clockwise about 17° with respect to the expected Miocene direction derived from the North American polar wander curve ($$\mathrm{inclination}\,=354^{\circ }$$ , $$\mathrm{declination}\,=30^{\circ }$$ ). According to biochronologic age, the magnetostratigraphic results from the mammal‐bearing sedimentary‐type section in the Suchilquitongo area can be correlated with chron C5Dn‐C5Cn3n at approximately 17.61–16.55 Ma. An age of about 17 Ma is proposed for the fossiliferous level, corresponding to an Early Miocene age.
Published Version
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