A NEW MODEL FOR HERRINGBONE CARBONATE PRECIPITATION BASED ON FINDINGS FROM THE EARLY CAMBRIAN OF SARDINIA

Author

Catherine CaterhamFollow

Date of Award

12-2024

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Linda C. Kah

Committee Members

Alycia Stigall, Julie Bartley, Molly McCanta

Abstract

Physicochemical conditions of precipitation are recorded in both the mineralogy and texture of carbonate cement. Marine cement phases, which precipitate directly from seawater, can therefore act as tracers for changes in either depositional environment or local water chemistry. Analysis of structurally distinctive marine cements that show discrete distributions in the geologic record additionally can aid in interpreting changes in marine ocean chemistry through time. Here we report a new discovery of herringbone carbonate (HBC; Sumner and Grotzinger, 1996) within Cambrian calcimicrobial and archaeocyath reefs of southwestern Sardinia. Petrography showed that HBC occurs in void spaces and shelter cavities within reef mounds of the Matoppa Formation (Nebida Group) and the Santa Barbara Formation (Gonessa Group). These void-lining and void-filling cements are comprised of interrelated radiaxial-fibrous calcite (RFC), fascicular-optic calcite (FOC), and herringbone carbonate (HBC). Although similar into radiaxial and fascicular-optic calcite, HBC is unique in its crystallography and appears as mm-scale light-dark crenulated banding with sweeping extinction along the length of each crystal. Sumner and Grotzinger attributed this phenomenon to the rotation of the c-axis relative to the direction of crystal elongation. Similarly, they associated the observed sweeping extinction in HBC with the neomorphic recrystallization of fibrous, non-parallel crystals. This fabric could be a useful tool when identifying variations in marine chemistry as the properties of HBC are well defined (Sumner and Grotzinger 1996a; Sumner, 1997; Kah and Bartley, 2021), the fabric is readily identifiable, and the spatial distributions of HBC are well constrained.

HBC was originally considered an Archean phenomenon (Sumner and Grotzinger, 1996) but has now been identified in a variety of Proterozoic and Paleozoic basins. The occurrence of HBC through time suggests recurrence of specific marine chemistries through time. The spatial and temporal distribution of HBC further suggests that increased alkalinity concentrations associated with locally persistent anoxic water bodies may drive HBC precipitation. Paleozoic occurrences of HBC, in particular, appear to be concentrated at the interface between a shallower, oxic water mass and a deeper-water, anoxic water mass that support a hypothesis that HBC precipitation is driven by interaction between chemically distinct water bodies.

Recommended Citation

Caterham, Catherine, "A NEW MODEL FOR HERRINGBONE CARBONATE PRECIPITATION BASED ON FINDINGS FROM THE EARLY CAMBRIAN OF SARDINIA. " Master's Thesis, University of Tennessee, 2024.
https://trace.tennessee.edu/utk_gradthes/12844