Investigation of Cretaceous-Tertiary (K-T) boundary channel deposits in
three sections in northeastern Mexico reveal three lithologically and
mineralogically distinct units separated by three or more
disconformities. The units include a spherule-rich layer (unit 1),
laminated sandstone (unit 2), and rippled sand and shale layers (unit
3). On the basis of paleontological, mineralogical, and geochemical
evidence, the K-T boundary is just above the top of unit 3. Although the
deposits have previously been interpreted as a tsunami deposit related
to a presumed K-T impact at Chicxulub on Yucatan, we have found no
evidence of a nearby impact. We suggest that deposition occurred in an
incised valley setting and over an extended period of time.