The diagram below represents a simplified and hypothetical geological cross-sect
ID: 802419 • Letter: T
Question
The diagram below represents a simplified and hypothetical geological cross-section, depicting the relationship of various sedimentary and igneous rocks beneath the surface. A cross-section is a slice through the Earth's crust and in this image you are looking at a side-view of the rock layers that exist beneath that surface. Different sedimentary rock layers are identified 'A' through to 'O', through units 'K' and 'G' are two different types of igneous intrusion. U_238/Pb_206 age dating the intrusion 'K' gave a date of 430 Million Years, age dating the intrusion 'G' gave a date of 490 Million Years and age dating 'A' gave 560 Million Years. Note, rock unit 'L' contains fossils (Ammonites), which are lower Jurassic age fossils. Note the presence of an Angular Unconformity at the base of rock unit 'L' You the need to refer to the Geological Time scale and apply one (or more) geological principal as you work through this assignment. Which is the oldest rock? Rock unit B Rock unit D Rock unit J Rock unit L Rock unit O What geological principle(s) did you use? crosscutting relationships Superposition Original horizontality Both(1) and b Both b and c Both a, b, and c Which is the oldest rock? Granite G Intrusion K Rock unit F Rock unit I Rock unit L What geological principle(s) did you use? Crosscutting relationships Superposition Original horizontality Both a and b Both b and c Both a, b and c Which is the youngest: Granite G or Rock unit L? Why? To which Geological Period/Periods do rocks unit 'G' & 'K' belong? Why? To which Geological ERA do to rocks units 'A' to 'J' belong? Which Geological PERIODS are missing between intrusion 'K' and rock unit 'L' in YEARS? Can rock unit 'L' be correlated across the French Girl Valley ? Why?Explanation / Answer
1 and 3 are correct
2) b and c
4) cross cutting relation
5) L because it has deposited after the unconformity
6) Paleozoic
7) Precambrian
8) Triassic
9) 230 my approximately