but i don't understand it entirely
Don't worry I'll get you there
Go the map, you will see that Boone County is on the Missouri River in the middle fo the state. Look at the colors on the map and go to the Legend on the right. You will see that Boone County has 3 geologic age periods.
We assign names to the geologic past, based on events that are distinct and marked at that time.
On that Missouri map on the other post;
Blue Green = Pennsylvanian geologic time = 286 - 320my ago
Blue = Mississippian geologic time = 320-360 my ago
Purple = Mixed Silurian and Devoian geologic time =360 -408 my ago
You can see from the map and the time scale that there is no goelogic record for Missouri 270 MY ago , which is Permain geolgoic time 245 - 286 my ago. Almost the strata in that county is 286 - 438 my old. You will not find this coral in the yellow area in Boone County