Temporal and spatial significance of volcanic particles in sand(stone): implications for provenance and palaeotectonic reconstructions

Volcanic particles have particular geodynamic significance. Despite abundant datasets on volcanicderived sand(stone), the distinction between spatial and temporal distribution of volcanic particles within the sedimentary record is poorly documented. One of the most intricate tasks in optical analysis of volcaniclastic sand(stone) is the distinction of grains eroded from ancient volcanic rocks (palaeovolcanic, noncoeval grains) from grains generated by active volcanism during sedimentation (neovolcanic coeval grains). Petrologic methods are useful for deciphering temporal significance of volcanic particles in detail between palaeovolcanic and neovolcanic, and for active volcanism to decipher syneruptive v. posteruptive processes during deposition in sedimentary basins close to volcanoes. Sedimentary processes during syneruptive, intereruptive and posteruptive phases are well described in continental environments in terms of changing sedimentary facies, for example, the architecture (from body scale to stratigraphic scale), width/depth ratios of palaeochannels, palaeosols and composition of fluvial-channel deposits, whereas they are less documented in deep-marine environments. Examples of volcaniclastic sedimentation derived from both palaeovolcanic and neovolcanic sources are found in diverse geotectonic settings.