Listen Base your answer on the cross-section below and your knowledge of Earth Science. The cross-section represents three
outcrops found several kilometers apart. The time period when cach sedimentary rock layer formed is shown. The symbols (star, circle, cross, square, and triangle)
represent fossils of different types of organisms present in the rock layers.
Outcrop 1
Outcrop 3
Permian
Outcrop 2
Pennsylvanian
Devonian
Pennsylvanian
Permian
X
X
Silurian
х
Mississippian
х
Devonian
o
X
Dovonian
O A
Ordovician
Camprian
Silurian
Give one characteristic that makes for a good index fossil.