Date of Graduation
Doctor of Philosophy in Space & Planetary Sciences (PhD)
John C. Dixon
Doy L. Zachry
Second Committee Member
Third Committee Member
Fourth Committee Member
Uniformitarian processes, governed by invariant physical laws, remain the most reliable source for reconstructing the past. Driving many of the repetitive, predictable processes are the orbital dynamics of the Sun-Planet-Moon systems. Astronomical periodicities range from a few hours (tides) to thousands of years (Milankovitch). These periodicities, combined with geomorphic observations of planetary surfaces, constrain the time-dependent processes and allow for reconstruction of events and conditions favorable for sedimentary accumulations. This research suggests that seasonal sedimentary processes are dominant on Titan and Mars, and have played a significant role in the formation of ancient banded-iron formations (BIF's) on Earth.
Earth, Mars, and Titan, the planetary bodies in our solar system with a history of flowing liquids, are characterized here to preserve seasonal and longer-period orbital signatures in layered strata. Surface features also suggest that volatile transient liquids, subject to solid phase sequestering, are dependent not only on climate forcing, but additionally on unique physiographic features of the planetary body. Climate change is subject to longer period orbital oscillations such as precession, eccentricity, and obliquity, and to the rise in or loss of surface liquids (oceans and seas) and atmospheres.
Thickness and mineralogy time-series profiles from the Dales Gorge Member of the Brockman Iron Formation suggest cycles and periodicities similar to modern current velocity profiles. First-order sinusoidal series patterns are interpreted as seasonal changes in bidirectional movement of ocean floor sediment, displaying second-order tidal influence. Sedimentary accumulations consist of iron-dominate organic sequences linked to slower current movement alternating with silica-dominate sequences indicative of modestly higher energy currents. Directional current oscillations may also contribute to changing mineralogy.
Titan and Martian's surfaces also demonstrate active seasonal processes. Rivers within Titan's northern polar region carry sediments from the more distal highland, through rugged foothills, to the lowland basins. Headward erosion during dynamic hydrocarbon seasonal rains carves the present valley and ridge systems on the flanks of the highlands. This research predicts that layered seasonal sedimentary varves have accumulated in the large endhoreic basin in the northern polar region of Titan.
Androes, Dixie Lee, "Orbital Periodicities Reflected in Ancient Surfaces of our Solar System and the Implications for a Record of Early Life" (2012). Theses and Dissertations. 560.