Radiocarbon dating can be used on sediments or sedimentary rocks that contain carbon, but it cannot be used on materials older than about 60 ka. Assume that a feldspar crystal from the granite shown in Figure 8.15 was analyzed for 40K and 40Ar.
What is the best way to date a sedimentary rock?
To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events.
Why is it difficult to assign a date to sedimentary rocks?
Terms in this set (48) Why is it difficult to assign a numerical age to a sedimentary rock? A radiometric date taken from a grain within a detrital sedimentary rock only gives the age of that one grain, which likely came from a source different from the other grains within the rock.
Can you radiometric dating sedimentary rocks?
Geologists use radiometric dating to estimate how long ago rocks formed, and to infer the ages of fossils contained within those rocks. Sedimentary rocks can be dated using radioactive carbon, but because carbon decays relatively quickly, this only works for rocks younger than about 50 thousand years.
Principle of original horizontality. Even if rock layers are presently folded, what law tells geologists that the rock layers were deformed after deposition? A nonconformity. What is the term for the boundary between a layer of sedimentary rocks overlying folded metamorphic rocks? A mold.
Why are sedimentary rocks hard to date?
Explanation: Radioactive elements decay at a certain constant rate and this is the basis of radiometric dating. Sedimentary rocks may have radioactive elements in them, but they have been re-worked from other rocks, so essentially, there radiometric clock has not been re-set back to zero.
How do scientists date sedimentary rock layers?
Geologists use radiometric dating to estimate how long ago rocks formed, and to infer the ages of fossils contained within those rocks. Sedimentary rocks can be dated using radioactive carbon, but because carbon decays relatively quickly, this only works for rocks younger than about 50 thousand years.
Put simply, an unconformity is a break in time in an otherwise continuous rock record. Unconformities are a type of geologic contact—a boundary between rocks—caused by a period of erosion or a pause in sediment accumulation, followed by the deposition of sediments anew.