From geomorphology to shape-fabric: The interplay of geomorphological controls and their spatial variability in the Teteltzingo lahar deposit, Citlaltepetl volcano (Mexico)

摘要

The distribution and characteristics of volcaniclastic deposits are the result of the interplay among numerous factors acting at different and multileveled scales of space and time. Such complexity requires multiple techniques for the study of volcanic regions. This approach provides a strong basis for understanding volcanic processes and their relationship with the resulting landforms or deposits and for reconstructing dynamic properties of flows. The aim of this paper is thus to understand the interplay between the geomorphologic environment and the origin and transport of large-magnitude debris flows. For this reason, we selected the eastern sector of the Citlaltepetl volcano and the Teteltzingo lahar event (Veracruz, Mexico). Information from geomorphological and morphometric analysis (including the linear features) was linked with field and shape-fabric data on selected outcrops. The study area was divided into three morphometric zones based on their elevation, slope, drainage network, and the trend in linear features. These zones are volcanic mountain zone, minor folded ranges and cumulative volcaniclastic plain. The geomorphological map enabled us to understand the origin of the landforms observed in each of the three morphometric zones. The characteristics of the Teteltzingo lahar deposit (i.e., geographic distribution, thickness and components) are associated with the morphologic and morphometric characteristics of the landscape. The particle shape-fabric analysis gave evidence that particle iso-orientation is consistent with the flow direction and orientation of some regional linear features, especially in the medial and distal zones. Moreover, the degree of iso-orientation was shown to be dependent on travel distance and particle diameter. The highest degree of iso-orientation was found in the coarse particles (gravel grain-size) throughout the entire deposit, being more developed in the distal zone. The evidence presented here suggests an interplay between geomorphological-structural controls and their spatial variability with the distribution of large-magnitude lahars. This highlights the importance of a multi-scale vision of mass movement phenomena that show how morphological and sedimentological characteristics are linked and could affect the generation and dynamics of future flows.