In the last few years improvements in technology have allowed geologists to date single grains of some minerals in rocks.A geologist separates 5 grains of the mineral zircon,which can be dated by the Uranium-lead method,and the crystal retains parent and daughter through weathering,erosion,and deposition.Thus,dating each mineral grain only gives the age of the source rock that was eroded,to produce that sand,from which the zircon grain is derived.The 5 grains yield ages of 160,110,2020,66,and 162 million years.What do these ages tell you about the age of the sedimentary strata?
A)They are Precambrian rocks,older than 2020 million years.
B)They are between 160 and 162 million years.
C)They are younger than 66 million years.
D)There are no age constraints from this data; sedimentary rocks cannot be dated by geochronology.

Question

Quizplus · Accepted Answer

The ages of the zircon grains range from 66 million years to 2020 million years, indicating that the source rock must be older than 66 million years but younger than 2020 million years. Therefore, the sedimentary strata must be younger than 66 million years. Option A is incorrect because there is no information provided on whether the rocks are Precambrian or not. Option B is incorrect because the ages of the grains do not indicate that the sedimentary strata is between 160 and 162 million years old. Option D is incorrect because sedimentary rocks can be dated by geochronology, but the age constraints in this case come from the zircon grains, not the sedimentary rocks themselves.

In the Last Few Years Improvements in Technology Have Allowed