Jeffrey W. Daniels HBSc thesis abstract
The Archean atmosphere is known only as bits and fragments – that often are at odds with each other, and certainly do not ultimately contribute to a “big-picture” composition of this atmosphere on the whole. That said, there is still far more literature available for the Archean atmosphere than there is for Archean-aged offshore sedimentary deposits; there is virtually nothing out there that attempts to connect the two aspects together.
Because there is such controversy over the most probable composition of the Archean atmosphere, at a glance this makes it very difficult to try to narrow down the individual components to their most likely concentrations. Comparing the Archean atmosphere to the present Martian one proved to be quite useful for this investigation – the only differences were for methane and water vapour, and being due to the presence of methanogens in the Archean Earth and to the simple size-difference between Earth and Mars (Earth’s larger size meant larger atmosphere which means more vapour), respectively.
Using data from the literature that has been produced concerning Archean-aged storm-related deposits, in particular of ripple formation, beaches (or lack thereof), and of hummocky cross-stratification, helped in constraining the average Archean surface temperature. From there, it was only a matter of plugging the now-constrained (relatively-speaking) atmospheric values into known and novel methods for determining the specifics of the dynamics of sediments of certain grain-sizes – in particular, using the Shields method.
After all was said and done, the final task was to try to make physical sense of the sedimentary dynamics results. The results themselves were consistent with each other, and helped to explain in particular, with some logic, why known hummocky bedding in Archean units appears so thin compared to present-day examples. The results predict that any eolian ripples and dunes found in the Archean should be noticeably smaller in size than more modern examples, and also predict that in general winds and storms should have been noticeably weaker during the Archean when compared to today.