Abstract:
Sources of ancient volcanic rocks are often unknown if they are either eroded and/or covered by younger
deposits. This problem, as well as the provenance of reworked volcaniclastic, fluvial and mass-flow deposits,
can be partially solved by the application of anisotropy of the magnetic susceptibility (AMS). For massive and
poorly sorted volcaniclastic rocks in particular this may be the only way of finding reliable transport directions
and therefore allowing for paleogeographic reconstructions. Here, we present a data set of 428 AMS
measurements and 249 measurements of sedimentary paleocurrent indicators from the Miocene Tepoztlán
Formation at the southern edge of the Transmexican Volcanic Belt (Central Mexico). The highest degree of
reliability of AMS measurements is gained for data from lava samples and the lowest from mass flows.
Sedimentary structures in sandstones and conglomerates such as trough cross-stratification, asymmetric
ripple marks, and the shape of scours and channels could be used to calibrate the results from AMS data
and to prove their reliability. AMS data on fluvial deposits point to a drainage systemwith aW–E flow direction,
indicating an outflow of the river system into the ancient Gulf of Mexico.
