Coal-derived rates of atmospheric dust deposition during the Permian

Abstract

Abstract.Despite widespread evidence for atmospheric dust deposition prior to the Quaternary, quantitative rate data remains sparse. As dust influences both climate and biological productivity, the absence of quantitative dust data limits the comprehensiveness of models of pre-Quaternary climate and biogeochemical cycles. Here, we propose that

Extreme eolian delivery of reactive iron to late Paleozoic icehouse seas

“…The large fluxes suggest remarkable atmospheric dust loading, an inference corroborated by the vast paleo-loess deposits of the Pennsylvanian-Permian-the thickest documented in the geologic record (Soreghan et al, 2008). While paleo-loess deposits so far only have been identified near the equator, using coal mineral matter as a dust proxy suggests significant dust deposition in Angara, North China, and West Gondwana even during interglacial intervals of the Permian, implying a global impact for dust (Large et al, 2015). Importantly, we can imagine vast coeval delivery of similarly bioavailable Fe to the oceans.…”

“…An important implication of this setting is that chemical fingerprints of this dust and its inferred bioavailability can be extrapolated to the vast loess and dust deposits preserved in the coeval continental record. Furthermore, these large volumes of continental dust suggest that parts of the ocean received similarly large Fe inputs (Large et al, 2015;Soreghan et al, 2015) with analogous bioreactivity. The section (Cisco unit) at Horseshoe atoll contains several glacioeustatic sequences (~18-24 m thick) separated by paleosols recording glacial (lowstand) conditions that exposed the buildups to dust fall, much like the Bahamian reef incorporates Saharan dust today.…”

Supplemental Material: Atmospheric dust flux in northeastern Gondwana during the peak of the late Paleozoic ice age

“…F distributions are based on 999 permutations. Marshall et al (2016) used two simulations (referred to as interglacial and glacial) with the Community Climate System Model version 3 (CCSM3) of dust emission, transport, and sedimentation with radiatively inactive dust and tuned them to one observation: a reconstructed dust deposition rate of 32 g/m 2 /yr -(3.2 g/cm 2 /kyr) in Middle Permian western Brazil. Each simulation used by Marshall et al (2016) was initialized from a modified version of a baseline simulation of late Paleozoic climate described in Heavens et al (2015).…”

“…Thus, tuning to the same deposition rate for both simulations enabled better identification of sources that differed between the simulations. (In addition, it was necessary, because Marshall et al (2016) did not attempt to attribute dust deposition in coals to glacial or interglacial intervals.) For better comparison with the paleogeography in which the reconstructions of dust deposition took place, the simulations were shifted 30º in longitude to the east.…”

“…For better comparison with the paleogeography in which the reconstructions of dust deposition took place, the simulations were shifted 30º in longitude to the east. Yet while Marshall et al (2016) considered the entirety of Permian time, the paleogeography used in the simulations was Asselian-Sakmarian (Early Permian) (Heavens et al, 2015) and so is appropriate for this study.…”