Topological invariance and spatial scaling of surface roughness in two highly eroded zones of Mexico: a comparative study

The Fractal Image Informatics toolbox (Oleschko et al., 2008 a; Torres-Argüelles et al., 2010) was applied to extract, classify and model the topological structure and dynamics of surface roughness in two highly eroded catchments of Mexico. Both areas are affected by gully erosion (Sidorchuk, 2005) and characterized by avalanche-like matter transport. Five contrasting morphological patterns were distinguished across the slope of the bare eroded surface of Faeozem (Queretaro State) while only one (apparently independent on the slope) roughness pattern was documented for Andosol (Michoacan State). We called these patterns ?the roughness clusters? and compared them in terms of metrizability, continuity, compactness, topological connectedness (global and local) and invariance, separability, and degree of ramification (Weyl, 1937). All mentioned topological measurands were correlated with the variance, skewness and kurtosis of the gray-level distribution of digital images. The morphology0 spatial dynamics of roughness clusters was measured and mapped with high precision in terms of fractal descriptors. The Hurst exponent was especially suitable to distinguish between the structure of ?turtle shell? and ?ramification? patterns (sediment producing zone A of the slope); as well as ?honeycomb? (sediment transport zone B) and ?dinosaur steps? and ?corals? (sediment deposition zone C) roughness clusters. Some other structural attributes of studied patterns were also statistically different and correlated with the variance, skewness and kurtosis of gray distribution of multiscale digital images. The scale invariance of classified roughness patterns was documented inside the range of five image resolutions. We conjectured that the geometrization of erosion patterns in terms of roughness clustering might benefit the most semi-quantitative models developed for erosion and sediment yield assessments (de Vente and Poesen, 2005).

El icnogénero Iguanodontipus en el yacimiento de “Las Cuestas I” (Santa Cruz de Yanguas, Soria, España)= The Iguanodontipus ichnogener in “Las Cuestas I” tracksite (Santa Cruz de Yanguas, Soria. Spain)]

Se define este icnogénero en el yacimiento paleontológico citado perteneciente al grupo Oncala de la facies Weald de la Cuenca de Cameros. El yacimiento de Las Cuestas I (Soria, España) es uno de los mayores del Grupo Oncala. Hasta el momento, se han catalogado en él casi 600 pisadas de ornitópodos, terópodos y, sobre todo, de saurópodos. Las huellas de ornitópodos son similares a las utilizadas para definir el icnogénero Iguanodontipus (Sarjeant et al., 1998) del Berriasiense de Dorset (Inglaterra), por lo que se incluyen en el mismo. Huellas semejantes a las descritas en este yacimiento se pueden ver en muchos otros del Grupo Oncala, tanto conocidos como inéditos. El análisis de los posibles icnopoyetas, autores de las huellas, indica que pudieron pertenecer a la familia Camptosauridae (Camptosaurus, Draconyx) o superfamilia Iguanodontoidea, de pequeño tamaño. Las Cuestas I (Soria, Spain) is one of the biggest tracksite in Oncala Group. Until the moment, it has been catalogued almost 600, ornithopod, theropod and mainly sauropod tracks. The ornithopod tracks are similar to those used to define the Iguanodontipus ichnogener (Sarjeant et al., 1998) from the Berriasian in Dorset (England), that is why they are also included.Very similar footprints to those described in this tracksite can be seen a lot of tracksites in Oncala Group, both known and unknown. They analysis of the potential trackmakers the tracks owners, reveals that they could belong to the family of Camptosauridae (Camptosaurus, Draconyx) or superfamily Iguanodontoidea, of small size.