Physical characteristics of hydrofracture systems and their fills in glacial sediments

Hydrofracture systems have been described in glacial sediments for almost a century and accelerating research since the 2000s, boosted by the advent of micromorphological techniques applied to glacial deposits, led to a significant rise of studies using paleo-hydrofractures (and their fills) as a new proxy for reconstructing glacial processes and environments. This review covers the great diversity of hydrofracturing context (subglacial, marginal, proglacial) and physical characteristics (at macro- to micro-scale) of hydrofracture systems and their fills based on a compilation of published and unpublished field-based data from both Quaternary and pre-Quaternary glacial sediments.

The text covers (1) the fundamental concepts of hydrofracturing processes including causes and triggers of overpressure in glacial environments as a preamble, (2) the physical characteristics of hydrofracture systems in glacial environments and (3) the parameters controlling these physical characteristics, (4) the characteristics of hydrofracture-fills, (5) the processes of sediment injection inferred from fill characteristics and (6) the wider implications of hydrofracturing and injection processes on paleoglaciological reconstructions. Future research perspectives, including the need for modeling of hydrofracture network in glacial environments, are finally discussed as it will certainly allow the role of ice thickness, slope and speed, meltwater input and host sediments in governing the architecture of hydrofracture systems to be untangled.