INVESTIGATING THE INFLUENCE OF DIATOMS ON THE TEXTURES OF COATED GRAINS FROM A CARBONATE SPRING IN NORTHERN CALIFORNIA

Diatoms are common in terrestrial freshwater carbonate environments, but their influence on the resulting carbonate textures remains unquantified. This study investigates the effect of diatoms on the syndepositional porosity of spring-associated carbonate coated grains from a freshwater spring in Henry Cowell State Park, northern California. Carbonate coated grains (n= 60) were collected from the distal-most pool facies of the spring (~ 300 m from the spring source) and the porosity of the 1 cm diameter fraction (n=20) was determined using the ImageJ software by adjusting the threshold size for pores >1000 µm². Results reveal a strong positive correlation between the number of pores and the number of diatoms examined in each coated grain (r=0.77). There is a moderate positive relationship between the length of the largest diatom and the minor axis diameter of a best fit ellipse of its corresponding pore (r=0.60). The total pore area for pores associated with at least one diatom was significantly greater than the total pore area of pores that did not enclose diatom frustules (t=1.80, p<0.05). Textural observations show that fine-grained laminated textures contain fewer diatoms than the porous textures suggesting that diatoms disrupt lamination continuity by introducing pore space. Seasonal geochemical water analyses will inform the effects of diatom growth on carbonate formation.