Late Triassic paleowinds from lacustrine wave ripple marks in the Fleming Fjord Group, central East Greenland

Geological evidence of paleoclimate conditions provide important constraints on paleoclimate models. Paleowinds are one of the central paleoclimate parameters in global circulation models used to reconstruct past climatic conditions. However, only a few climate proxies such as eolian dunes and shallow-water wave ripples provide information on paleowind directions. In this study, we present new paleoclimatic data based on lacustrine sediments with wave ripple marks in the Upper Triassic Fleming Fjord Group, central East Greenland deposited at very shallow water depth in the northern part of Pangaea in a mid-latitude, warm-temperate climate. Wave-ripple orientations are measured on 380 individual fossilized wave-rippled beds at four localities in the -8500 km2 lacustrine basin. These ripple data are used to establish a geologic wind proxy and are compared to previously published general circulation models. Two wave ripple orientations are observed: The dominant ripple orientation and wave ripple characteristics indicate paleowinds from the Late Triassic SSE and NNW (154.5 degrees and 334.5 degrees), while a subordinate orientation indicate paleowinds from W or E (270 degrees or 90 degrees). This paleowind regime remained stable for at least -7.5 million years during the mid-late Norian (218.5-211 Ma). These results correspond very well with some general circulation model results that suggest summer winds from the NNW and winter winds from the SSE. Based on the great compatibility between empirical data and general circulation model results, the wind pattern seems to have been greatly influenced by regional, Late Triassic mountain topography in the present-day Greenland and Norway channeling the paleowind in the northernmost part of the pre-Atlantic rift basin (the mid-Norwegian-east Greenland rift system).

Automated summary

Geological evidence of wave ripple marks in lacustrine sediments from central East Greenland provides new paleoclimatic data on paleowind directions during the Late Triassic period, showing stable paleowinds from the SSE and NNW directions for at least 7.5 million years. This corresponds well with general circulation model results suggesting NNW summer winds and SSE winter winds, influenced by Late Triassic mountain topography in present-day Greenland and Norway.