Intro to Graphic Correlation Fossils and Evolution 870:125

Loc. A 100 miles Loc. B 6 5 4 3 2 1 1 2 3 4 5

Loc. A Loc. B 100 miles 5 4 6 5 3 4 2 3 1 2 1 Top 4 Base 4 Base 3

6 5 4 3 2 1 1 2 3 4 5

5 + 5 4 top of #4 + 4 6 5 3 base of #4 + 3 4 2 + 2 3 2 1 + 1 1 5 4 3 2 1

Selecting Line of Correlation Select line so that: It goes through at least some points (ideally bases or tops that are known to have biostratigraphic integrity) Bases not on line are to the left Tops not on line are to the right Assumption: Standard Reference Section is depositionally continuous and fossil ranges are relatively complete

Graphic Correlation + + + Loc. A + Line of correlation + 5 + 4 6 5 + 3 4 Loc. A + 2 Line of correlation 3 2 + 1 1 Standard Reference Section

Significance of LOC + + Section 2 + + + Standard Reference Section 5 + 4 Slope of LOC is the average relationship between rate of deposition in the two sections being correlated If LOC is correct, any point in one section can be correlated to its precise equivalent in the other section 6 5 + 3 4 Section 2 + 2 3 2 + 1 1 Standard Reference Section

Significance of LOC LOC may be a straight line if two sections being correlated are both depositionally continuous and if there is a constant relationship between rates of deposition in each LOC may change slope if rate of deposition changed in one section relative to the other Horizontal terrace in LOC indicates an unconformity (depositional hiatus or erosion) in one section

Significance of LOC SRS SRS hiatus or erosion at other section while deposition continued at SRS increase in rate of deposition at SRS relative to other section SRS SRS

Compositing and updating the SRS + 5 add top of #6 + 4 5 + 3 4 Section 2 6 2 raise top + lower base add base of #6 2 3 + 1 1 Standard Reference Section

Compositing and updating the SRS Once range adjustments and range additions have been completed, the SRS becomes a Composite Standard Reference Section

PAST data file for Loc A vs. Loc B