Temperate glaciation on a Snowball Earth

Author(s)
T. M. Vandyk, G. Wu, B. J. Davies, Y. Xiao, M. Li, G. A. Shields, D. P. Le Heron
Abstract

Ubiquitous glaciation was the hallmark of the Cryogenian Period (ca. 720–635 Ma), therefore understanding the character, behaviour, extent and configuration of Cryogenian ice bodies is a fundamental requirement in reconstructing climates and environments from the period. Unfortunately, despite abundant evidence for glaciation, there is a strong preservational bias towards basinal glaciogenic sedimentary strata and against subglacial strata. In particular subglacially striated surfaces, owing to their fragile millimetre-thickness, are very rare and represent only a tiny proportion of the global Cryogenian outcrop area. Thermal regime is one of the most important controls of glacial behaviour and subglacially striated surfaces are one of the very few means of determining an ancient temperate thermal regime. In this context we present sedimentological and detrital zircon detail of a fortuitously preserved Cryogenian (Marinoan) outcrop in the Aksu-Wushi area of the Tarim Craton, NW China. The Yuermeinak Formation preserves not only a subglacially striated surface and palaeotopography but also a thin, locally preserved, subglacial tillite. Together these indicate grounded ice. The remaining formation reveals glacial retreat and deposition of predominantly supraglacially-sourced debris within a dynamic, open-water, ice-proximal proglacial environment. A palaeogeographic reconstruction is proposed in which the Aksu-Wushi area developed from a deeper-water basinal environment, without clear evidence for glaciation, during the early Cryogenian, to an area of mountainous uplift with nearby grounded glacial ice, during the latter Cryogenian. Combining detrital zircon data of this study with published data it is further proposed that this development was linked to an active margin setting, either through expansion of an Andean-type mountain range to the north of the study area or flank-uplift of a back-arc basin.

Organisation(s)
Department of Geodynamics and Sedimentology
Journal
Precambrian Research
Volume
331
ISSN
0301-9268
DOI
https://doi.org/10.1016/j.precamres.2019.105362
Publication date
09-2019
Publication status
Published
Peer reviewed
Yes
Austrian Fields of Science 2012
105106 Geodynamics
ASJC Scopus subject areas
Geology, Geochemistry and Petrology
Portal url
https://ucris.univie.ac.at/portal/en/publications/temperate-glaciation-on-a-snowball-earth(25baa5ee-d0d0-4e3d-9262-d0805b0c7dd5).html