ABSTRACT This field trip examines Paleoproterozoic basement, Neoproterozoic metasedimentary strata, and crosscutting Mesozoic intrusive rocks at Frazier Mountain, Placerita Canyon, and Limerock Canyon in the western San Gabriel Mountains block, California. We present new U-Pb zircon geochronology results that constrain the Proterozoic through Cretaceous tectonic and magmatic history. The excursion ends in San Antonio Canyon in the eastern San Gabriel Mountains where several large rock avalanche deposits are sourced from distinct basement rocks. 10 Be surface exposure ages and post-infrared infrared stimulated luminescence burial ages demonstrate late Pleistocene to Holocene movements for these landslides.

Abstract The NW African continental margin is well known for the occurrence of large-scale but infrequent submarine landslides. The aim of this paper is to synthesize the current knowledge on submarine mass wasting off NW Africa with a special focus on the distribution and timing of large landslides. The described area reaches from southern Senegal to the Agadir Canyon. The largest landslides from south to north are the Dakar Slide, the Mauritania Slide, the Cap Blanc Slide, the Sahara Slide and the Agadir Slide. Volumes of individual slides reach several hundreds of cubic kilometres; run-outs are up to 900 km. In addition, giant volcanic debris avalanches are widespread on the flanks of the Canary Islands. All headwall areas are complex with clear indications of multiple failures. The most prominent similarity between all investigated landsides is the existence of widespread glide planes that follow the stratigraphy, which points to weak layers as most important preconditioning factor for the failures. Landslides with volumes larger than 100 m 3 are close to being evenly distributed over time, contradicting previous suggestions that landslides off NW Africa occur at periods of low or rising sea level. The risk associated with the landslides off NW Africa, however, is relatively low due to their long recurrence rates.

Abstract This paper presents a Geographic Information System catalogue of the submarine landslides of the Spanish continental margin and describes the problems associated with harmonizing the catalogue with its onshore homologue. The data model structure is described to explain how to apply the rules and specifications following the Infrastructure for Spatial Information in Europe (INSPIRE). Because of the singularities of the marine environment compared with those of land, integrating the submarine landslide catalogues into INSPIRE specifications requires the following procedures: (1) simplification of the list of values of state of activity into three categories: active, dormant and relict; and (2) inclusion of debris avalanches and turbidites as new typologies of landslides. This paper discusses the problems associated with harmonizing different data types and units from different sources, such as the thickness (metres and seismic two travel time) or the age of the event, and a numeric code for the geological timescale is proposed to harmonize these data. We establish whether an item is required based on the reliability of the landslide event, which is categorized by three levels (high–middle–low) depending on the precision of the data source, methodology used and quality of the publication where the data are obtained.

Abstract In glacier-fed Baspa River valley, Late Quaternary climatic changes are archived in the terraces, fan and landslide deposits. An initial optically stimulated luminescence (OSL) based stratigraphy of these deposits is developed to deduce geomorphic evolution and palaeoclimatic changes. The data show large alluvial fan progradation around Sangla till c. 45 ka (middle of marine isotope stage 3 or MIS-3) due to glacial retreat and readjustment of glacigenic sediment under warm and humid conditions followed by incision. During the end phase of MIS-3 (>23 ka), intensified precipitation blocked the river course near Sangla and Kharogla by rock avalanches and imposed lacustrine conditions which recorded sedimentation until the beginning of Holocene ( c. 11.4 ka). Reduced sedimentation in these lakes during the last glacial maximum (LGM) c. 23–18 ka suggests a cold and arid climate, whereas increased sedimentation during c. 18–11.5 ka indicates a warm and humid climate post-LGM. A palaeolake breach occurred during early Holocene and incision continued throughout the Holocene, with a pulse of fluvial aggradation during c. 9.1–6.5 ka over lacustrine remnant. In the upper reach of the valley (Chitkul area), coeval aggradation continued from >28 ka until c. 19 ka (MIS-3 to LGM) under cold and relatively arid conditions. This study emphasizes that Late Quaternary geomorphic evolution of Baspa valley is well synchronous with glacial fluctuations and the rapid response of the glacifluvial system to Indian summer monsoon (ISM) dynamics.

Geologic mapping at the base of Volcán Barú, Panama, characterizes two large andesitic volcanic debris avalanche deposits attributed to sector collapse at Volcán Barú. The older Caisán debris avalanche deposit is at or beyond the radiocarbon dating range, >43,500 yr B.P., whereas the younger Barriles debris avalanche deposit is constrained by two radiocarbon ages that are ca. 9000 yr B.P. The total runout length of the Caisán deposit was ~50 km, covering nearly 1200 km 2 . The Barriles deposit extended to ~45 km and covered >990 km 2 , overlapping most of the Caisán. Over 4000 hummocks from these deposits were digitized, and statistical analysis of hummock location and geometry depicts flow patterns of highly fragmented material affected by underlying topography and also helps to define the shorter runout limit of the Barriles deposit. The Barriles and Caisán deposits are primarily unconfined deposits that are among the world's most voluminous subaerial debris avalanche deposits. Two different geospatial procedures, utilizing deposit thicknesses and edifice reconstruction, yield calculated volumes ~30 km 3 and larger for both deposits. Subaerial deposits of comparable scale include those from Mount Shasta, Socompa, and Shiveluch. Currently, the modern edifice is 200–400 m lower than the estimated precollapse Barriles and Caisán summits, and only 16%–25% of the former edifice has been replaced since the last failure. The ~10 km 3 postcollapse lava-dome complex, however, implies a Holocene magma production rate of 1.1 km 3 /k.y., comparable to elevated eruptive pulses documented at other stratovolcanoes, underscoring the importance of hazards assessment and monitoring of this active volcano.