Obliquity-Dominated High-Latitude Continental Triassic-Jurassic Climate, from the Coal-Bearing Junggar Basin, (Ürümqi, China)
Abstract:Sedimentary facies-based climate proxy data from the thick, coal-bearing, fluvial-lacustrine Haojiagou and Badaowan fms. of the high-paleolatitude (55-65° N) Junggar Basin of northwestern China show that Late Triassic and Early Jurassic (~210-190 Ma) high latitude climate variability was strongly paced by obliquity cycle-dominated (~40-50 ky) orbital variations (1), based on an age model using the 405 ky cycle of eccentricity and the end-Triassic extinction tie point (2,3). In contrast, contemporaneous low-latitude continental climate was nearly exclusively paced by climatic precession, with virtually no hint of obliquity (4). While obliquity-dominance at high latitude is not necessarily unexpected, the envelope of variability of eccentricity, as well as its period (for cycles > 405 ky) at both high and low latitudes deviate in major ways from the expectations of current numerical solutions of orbital variations (5), but is consistent with chaotic diffusion of the Solar System (6), while our preliminary data also suggest that the Earth-Mars orbital secular resonance was in today’s 2-to-1 ratio of eccentricity to inclination periods (5). Previously unknown, this obliquity-dominated, non-analog climate variation in the apparently warm and glacier-free high-latitudes of Pangea, coupled with documented low-latitude climatic precession-dominated climate variation, provides a glimpse of an empirical basis for mapping the behavior of the Solar System during times when its behavior was significantly different than present day. This is a contribution to IGCP 632 (Continental crises of the Jurassic).
1, Sha+, 2010, Earth Sci. Frontiers 17:22; 2, Sha+, 2011, Acta Geol. Sinica 85:421; 3, Blackburn+, 2013, Science 340:941; 4, Olsen & Kent, 1996, Palaeogeo. Palaeoclim. Palaeoeco. 122:1; 5, Laskar+, 2011, A&A 532:A89 DOI:10.1051/0004-6361/201116836; 6, Laskar, 1999, Phil. Trans. Roy. Soc. London A 357:1735.