NEW INSIGHTS FOR DETERMINING RELATIVE TECTONIC UPLIFT USING HIGH-RESOLUTION TOPOGRAPHIC DATA

Vertical movements in dissected areas from continental active margins, can be determined using statistical methods of geomorphological and geological data that provide numerical values about the relative variations between adjacent blocks. In tectonically active areas, river profile analysis and valley incision can be used as indicators of tectonic deformation and relative elevation changes of the bedrock at short time scales. Unfortunately, these techniques have traditionally focused on area-slope relationships that difficult to understand the association between morphology and tectonic movements.

A new surface plotting method for relative incision anomalies has been implemented to identify actively deforming regions, using data from fluvial deep incision and valley half-width, which can be calibrated to the lithology. The main objective of this work is to analyze the morphology of tectonically active areas, with the help of quantitative geomorphology using statistical techniques applied to digital elevation model (DEM) of 4-m grid, aerial photographs, geological maps, slope maps and field observations. The treatment of data allows to determine the relative displacements and the kinematics along the block boundaries.

During the development of this work a GIS software has been applied to the DEM data as follow: 1) the extraction of the incision data from the relief (valley depth + valley half-width) along river profiles to each lithology, 2) the generation of power law fits with the data extracted for each lithology according to the method of Bonnet et al. (1998), 3) the profile morphometry calculation along river profiles using the vertical, horizontal and total deviation from the theoretical logarithmic river profile and its stream length gradient index (SL) and 4) interpolation and generation of the anomaly map of relative uplift from the new data.

The present methodology was applied along the entire Ecuadorian coastal margin (including the Coastal Cordillera). The results obtained were compared with SL data, demonstrating that the method developed is quite sensitive to detect the vertical distribution of the movement on landscapes. In addition, this is a relatively cheap method that applied it can provide interesting information.