Deeply incised drainage networks are thought to be robust and not easily
modified, and are commonly used as passive markers of horizontal strain.
Yet, reorganizations (rearrangements) appear in the geologic record. We
provide field evidence of the reorganization of a Miocene drainage
network in response to strike-slip and vertical displacements in
Guatemala. The drainage was deeply incised into a 50-km-wide orogen
located along the North America-Caribbean plate boundary. It rearranged
twice, first during the Late Miocene in response to transpressional
uplift along the Polochic fault, and again in the Quaternary in response
to transtensional uplift along secondary faults. The pattern of
reorganization resembles that produced by the tectonic defeat of rivers
that cross growing tectonic structures. Compilation of remote sensing
data, field mapping, sediment provenance study, grain-size analysis and
Ar(40)/Ar(39) dating from paleovalleys and their fill reveals that the
classic mechanisms of river diversion, such as river avulsion over
bedrock, or capture driven by surface runoff, are not sufficient to
produce the observed diversions. The sites of diversion coincide
spatially with limestone belts and reactivated fault zones, suggesting
that solution-triggered or deformation-triggered permeability have
helped breaching of interfluves. The diversions are also related
temporally and spatially to the accumulation of sediment fills in the
valleys, upstream of the rising structures. We infer that the breaching
of the interfluves was achieved by headward erosion along tributaries
fed by groundwater flow tracking from the valleys soon to be captured.
Fault zones and limestone belts provided the pathways, and the aquifers
occupying the valley fills provided the head pressure that enhanced
groundwater circulation. The defeat of rivers crossing the rising
structures results essentially from the tectonically enhanced activation
of groundwater flow between catchments.