Evidence of paraglacial and paraperiglacial crisis in Alpine sediment transfer since the last glaciation (Ticino, Switzerland)

• Published in: Quaternaire
• Main Author: Scapozza, Cristian
• Format: Article in Journal/Newspaper
• Language: English
• Published: Association française pour l’étude du quaternaire 2016
• Subjects: remplissage des vallées et des lacs; éboulisation; Tardiglaciaire; Holocène; Alpes suisses; valley and lake fillings; rockwall erosion; Lateglacial; Swiss Alps; geo; envir; Arctic; permafrost; Subarctic
• Online Access: https://doi.org/10.4000/quaternaire.7805; http://journals.openedition.org/quaternaire/7805

The “paraglacial” and “paraperiglacial” concepts were introduced in the second half of 20th Century for describe processes, landforms and deposits directly conditioned by deglaciation (paraglacial), respectively by permafrost degradation (paraperiglacial). They represents theoretical models describing the transition from glacial to periglacial, or more generally non glacial conditions (paraglacial model), and from periglacial to temperate conditions (paraperiglacial model). Evidences of sediment transfer conditioned by these processes were described in particular in the Arctic and Subarctic domains. These evidences are less generalised in the Alps and they consider rarely both concepts, integrating periglacial landforms and deposits in source to sink sediment transfer in a single catchment. Here we present evidences of para(peri)glacial sedimentary crises by quantifying sediment transfer from the periglacial zone to the delta in Lake Maggiore for the Ticino River catchment (southern Swiss Alps). Compilation and revision of chronological data, the assessment of sedimentation rates in the Ticino Valley, of progradation rates of the Ticino River delta and of rockwall erosion rates in the periglacial zone, allowed empirical models of sediment transfer to be produced. These models highlights significant high sedimentation rates in the valley floor during the beginning of the deglaciation, and significant rates of rockwall erosion during periods of intense temperature warming and intense permafrost degradation (such as at the beginning of Bølling and during the Preboreal), showing a very good correspondence with paraglacial and paraperiglacial theoretical models. Sediment transfer evolution during the entire Lateglacial and the first half of Holocene in the southern Swiss Alps may then be explained by a combination of a paraglacial erosion phase related to the deglaciation and of two paraperiglacial erosion phases related with significant periods of temperature warming during the Bølling/Allerød and the first part of ...