Age and origin of the continental Teocaltiche paleo-basin, Mexico
Por:
Gonzalez-Cervantes, Norma, Jorge Aranda-Gomez, Jose, Carranza-Castaneda, Oscar, Ortega-Obregon, Carlos
Publicada:
1 dic 2019
Categoría:
Geology
Resumen:
An extensive lake existed during part of the Oligocene and almost all
the Miocene in the region located east of the southern end of the Sierra
Madre Occidental (SMOc). The lake was formed in a tectonic depression
associated with the Aguascalientes graben and the Teocaltiche
half-graben. Sediments accumulated inside this continental basin are
epiclastic, mainly derived from volcanic rocks of the SMOc, and from the
volcanic cover of the Mesa Central, chemical and biochemical
precipitates (fresh water limestone), and mixed sediments, as well as
far less voluminous, but ubiquitous, volcanic ash-fall layers, which
were used to obtain U-Pb ages from zircons. The age range of the
basin-fill sediments is broad, varying from Rupelian (similar to 28.6
Ma) to Tortonian (similar to 7.6 Ma). Previously, on the basis of fossil
fauna, the succession was considered only as late Miocene in age.
The southern end of the SMOc includes several NNE-trending basins of
tectonic origin that contained lakes. Based on the characteristics of
the individual sedimentary successions, and on their fossil faunas, it
is known that three of these basins (Tlaltenango, Juchipila and
Teocaltiche) had lakes at the same time. The fourth basin, the Bolanos
graben, located west and parallel to the Tlaltenango basin, probably
also had a lake during the Neogene, but almost all its sediments have
been eroded, so that little is known about them. In order to explain the
simultaneous partial closure of all the drainage systems a common,
regional, cause must be invoked. All the tectonic basins in the southern
part of the SMOc end close to the tectonic depressions related to either
the Tepic-Zacoalco or Tula-Chapala rifts. Isostatic uplift of the foot
wall blocks of these similar to E-W- trending rifts may have provoked
partial closure of hydrologic systems within the NNE-trending grabens.
It is not known when the basins were opened and ceased to act as
aggrading systems, but the apparent absence of Blancan age fossils
within them may indicate that they could have been opened prior to
similar to 4.75 Ma, which is the numerical value of the beginning of
this faunal stage. A probable common cause for the simultaneous opening
could be a marine invasion in the region now occupied by the Gulf of
California. The new base level of erosion probably increased the stream
gradients in the fluvial systems, providing enough energy to the axial
rivers within the grabens to overcome the uplift associated with similar
to E-W rift activity.
Filiaciones:
Univ Nacl Autonoma Mexico, Posgrad Ciencias Tierra, Blvd Juriquilla 3001, Queretaro 76230, Qro, Mexico
Univ Autonoma Aguascalientes, Dept Ingn Civil, Ave Univ 940, Aguascalientes 20131, Ags, Mexico
Univ Nacl Autonoma Mexico, Ctr Geociencias, Blvd Juriquilla 3001, Queretaro 76230, Qro, Mexico
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