Notes on the origin of extensive endorheic regions in central and northern Mexico, and some implications for paleozoogeography
Por:
Aranda-Gómez J.J., Carranza-Castañeda O., Wang X., Tseng Z.J., Pacheco-Castro A.
Publicada:
1 abr 2018
Resumen:
The recent discovery of a fossil of Enhydritherium terraenovae in upper
Miocene fluvial deposits in Juchipila (Mexico), nearly 200 km away from
the nearest coast, together with other known occurrences of the same
species in Florida and California, made possible to envision an
alternative to the Panamanian and Polar routes of migration through
fluvial systems in Mexico. In order to cross from one ocean to the
other, individuals of E. terraenovae must have passed the continental
divide, which is a physiographic feature that separates surface waters
that flow into the Atlantic and Pacific versants.
Two vast endorheic regions, which together span more than 400,000 km(2)
in area, currently dominate drainage systems in northern and central
Mexico. The endorheic regions are broadly bounded by two mountain ranges
and coincide with the arid and semi-arid regions of the Chihuahuan
desert. These closed basins are an additional obstacle for migration.
However, drainage systems are constantly varying and adjusting to
changing conditions imposed by climate, tectonic activity, volcanism,
and pronounced asymmetries in topography and rainfall distribution. The
migration route across Mexico for Enhydritherium terraenovae in the late
Miocene (>= 6 Ma) could have been facilitated by one or more river
captures that inverted the flow direction near the headwaters of a
drainage system that debouched either into the Gulf of Mexico or the
Pacific coast.
Biologists studying fresh water fish faunas in the southern part of the
United States and in northern and central Mexico have documented several
living species that occur in both the Rio Grande and in the Mezquital
rivers, two drainages that are not presently connected, drain in
opposite directions (i.e. towards the Gulf of Mexico and the Gulf of
California, respectively) and are separated by the endorheic regions.
Furthermore, systematic studies of fresh water fish faunas in the region
has numerous examples of endemicity and allopatric speciations that are
interpreted as evidence of several events of drainage system
rearrangement either by stream capture, beheading, or river diversion or
by fragmentation caused by formation of closed basins by faulting,
volcanic activity or isostatic rebound in the footwall block of normal
faults.
The western boundaries of the extensive endorheic regions in Mexico are
controlled mainly by a highland produced by intense felsic volcanism
during the Sierra Madre Occidental activity (Eocene - Miocene), and the
eastern hydrological divide coincides with mountains associated with the
fold and thrust belt produced by the Hidalgoan orogeny in early Cenozoic
time. Normal faulting associated with Basin and Range extension formed
additional closed basins. Another major factor in the formation of the
endorheic regions is the terminal Miocene climate change, which caused
runoff reduction and lowered the rivers capacity of erosion.
Opening of the Gulf of California changed the overall slope of rivers
draining into the Pacific in northwestern Mexico triggering the capture
of rivers formerly confined to the closed basins or draining to the Gulf
of Mexico. Quaternary normal faults have been documented a few tens of
kilometers from the hydrological divides of the endorheic regions,
suggesting that in some regions there is an active tectonic component in
their formation.
The location of the crossing point for the otters is uncertain as the
fossil record is scant and investigation on the evolution of drainage
systems through time in Mexico is in the early stages. However, it is
argued that there is a fair chance that the crossing occurred via the
Mezquital river capture near Durango city. Isotopic age of the sediments
where the Enhydritherium terraenovae fossil was collected, imply that
the capture must have occurred in the late Miocene. (C) 2018 Elsevier
Ltd. All rights reserved.
Filiaciones:
Centro de Geociencias, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, Qro., Querétaro, Mexico
Department of Vertebrate Paleontology, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA, United States
Department of Pathology and Anatomical Sciences, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
Postgrado en Ciencias de La Tierra, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, Qro., Querétaro, Mexico
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