Macro-fabric analysis in relict rock-glaciers, Cantabrian Mountains (NW Spain)1st International Conference on Research for Sustainable Development in Mountains Regions (2016)
Approximately 180 relict lobate and tongue-shaped rock glaciers are widespread in the Cantabrian Mountains, indicating past permafrost distribution in these mid-latitude mountains. They ere primarily located within glacial cirques, facing north and northeas, at the foot of quarzites and sandstones escarpments and over 1600 m, with some exceptions. Surficial macro-fabric analysis of over 40 rock glaciers including both ridges and furrows were conducted. In each case the orientation and dip of 50 clasts was determined. Only clasts over 10 cm (normally 20 cm) and L/W ratios over 1,5 where measured. All data was represented in equal-area nets providing information about fabric distribution. Eigenvalues were also calculated for each sample. In a few scenarios, exposures in the rock glaciers allowed internal macro-fabric and grain size analsysis to be conducted, something very rare in the literature. Data presents weak fabric in furrows, but dominant clast alignments in ridges, showing parallel and, in sime cases, perpendicular alignments to the rock glacier paleoflow. These differences are likely related with compresive flow in the ridges and extensional flow in the furrows. Clast collapse and mobilization may also occur after the rock glacier ice melts but generally they maintain their original form. When compared wuith active rock glaciers they shown similar dynamics. Significant differences between lobate and tongue-shaped rodk glaciers were observed, problably related ti the greater size of the second. Lithology also had an influence in rock glacier shape preseration with quartzite-composed rock glaciers being better preserve than sandstone rock glacier. Rock glaciers with others type of lithology are quite rare, probably due to post depositional modification.
Macro-fabric analysis in relict rock-glaciers, Cantabrian Mountains (NW Spain).
Citation InformationRosa Blanca González-Gutiérrez, Javier Santos-González, João A. Santos, José María Redondo-Vega, et al.. "Macro-fabric analysis in relict rock-glaciers, Cantabrian Mountains (NW Spain)" 1st International Conference on Research for Sustainable Development in Mountains Regions (2016)
Available at: http://works.bepress.com/joao-santos/27/