Lillie Spates

Mentor: Dr. Anthony Chappaz
Research: Depositional Conditions of Late Cambrian Stromatolites

Stromatolites from the Late Cambrian provide key insight into ancient environmental conditions and the chemical factors that supported early microbial communities. In the Point Peak Member of the Wilberns Formation at Honey Creek, Mason County, Texas, microstromatolite biostromes display a repeated pattern of alternation between pale microstromatolite–dendrolite frameworks and a dark, glauconite-bearing bioclastic matrix. Because glauconite typically forms under suboxic conditions, this pattern raises the question of whether seawater oxygen levels fluctuated during deposition. This study will investigate whether these two fabric types show differences in mineralogy and trace-element chemistry consistent with changing redox conditions. Two matched polished slabs from each hand specimen will be analyzed using X-ray diffraction (XRD) and micro-X-ray fluorescence (μXRF) mapping to identify mineral phases and document elemental distribution. Together, these methods will evaluate whether the two fabric types formed under different geochemical regimes.