GEOL 2530 Lecture Notes - Lecture 3: Diagenesis, Petrography, Image Analysis
14 Apr 2016
School
Department
Course
Professor
Document Summary
Frequency of occurrence (wt %) - grain size ( ) Cumulative curve - vs. cumulative wt % Most grain-size distributions not lognormal environmental interpretations. Mean - arithmetic average of all particle sizes graphic mean size mz. Spread of grain sizes around mean (a) visual estimate chart (b) standard deviation inclusive graphic standard deviation. I phi standard deviation very well sorted well sorted moderately sorted poorly sorted very poorly sorted extremely poorly sorted. 4. 0 e. g. dune, beach sands ~0. 20 to 0. 25 glacial till, mudflows ~5 to 8 : skewness. 5 e. g. river sands + skewness beach sands - skewness: kurtosis. Little use in environmental interpretation: method of moments. Krumbein and pettijohn (1938) weight frequency x a distance. 3. 4 applications of grain size data: description. 4 (a) graphical dissection of cumulative curves e. g. visher (1969) - beach samples. 4 lognormal populations transport controls e. g. bjorlykke (1989) - skewness vs sorting.
