Sedimentary rock is composed of the weathered remains of a variety of rocks of all ages. It would therefore only be possible to date specific components of a sample, none of which would equate to the age of the sedimentary rock as a unit. Sedimentary rock is dated by its association in the geologic column with igneous and metamorphic rock which can be dated by radioactive dating techniques.
Sedimentary rock can only rarely be dated directly by radiometric means. A sedimentary rock may include particles that contain radioactive isotopes, but the rock's age cannot be accurately determined because the grains making up the rock are not the same age as the rock in which they occur. Rather, the sediments have been weathered from rocks of diverse ages.
Because of geologic events such as plate tectonics and volcanism, suitable material for radiometric dating, such as volcanic tuff, solidified lava, and igneous intrusions have been found as layers on, in, and cut through layers of sedimentary rock. Intrusions are always younger than the rock body they penetrate, meaning that the sedimentary rock in which intrusions are found will be older than a radiometrically dated sample of the intrusion. Lava flows and volcanic ash which form layers in rock will be younger than the rock below and older than the rock above. The solidified intrusions and lava flows can be dated with radiometric techniques.
The radiometric dating of suitable rocks (i.e. igneous or metamorphic) in proximity to their sedimentary counterparts, therefore allows the sedimentary rock to be dated as well.
How_do_you_determine_the_age_of_a_sedimentary_rock_or_a_fossil_contained_within_it
It is difficult to determine the absolute age of a sedimentary rock because sedimentary rocks are made up of diverse particles that are all different ages. As a result radioactive dating can only determine the age of the particles, not the whole rock.
Because most sedimentary rocks are composed of sediment which derived from many sources any dating process would find many different results. For example, a zircon from a sedimentary rock may have been formed in an igneous rock many hundreds of millions of years before. Testing the zircon would give the date of the igneous rock, not the sedimentary.
It is much safer to find the nearest contemporary igneous rock in the sequence and date that, even a thin layer of volcanic ash will do.
Because the rock formation is easily weathered away by water and wind. This causes parts and peices to be carried away, where they can reform into newer formations.
Unconformities represent missing layers which could have eroded or were not deposited.
because they are different
That the one below the other is generally older.
They CAN be used to determine accurate absolute ages.
i bird
Radioactivity
They can use either radiometric dating or magnetostratigraphy.
fossils can be used to determine the relative age of rock layer by using the classification of fossils to find the relative ages of rocks in which fossils are found. :] hoped i helped you out.
fossils can be used to determine the relative age of rock layer by using the classification of fossils to find the relative ages of rocks in which fossils are found. :] hoped i helped you out.
An unconformity is defined as a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. The different types of unconformities include disconformity, nonconformity, angular unconformity, paraconformity, buttress unconformity, blended unconformity, and biconformity.
A geologist uses the principle of superposition to determine the relative ages of rocks and sedimentary layers. This principle states that in undisturbed layers of rock, the youngest layers are at the top while the oldest layers are at the bottom. By observing the order in which different rock layers are stacked, a geologist can infer the sequence of events that happened over time in a particular location.
They studied fossils and applied the principle that old layers of rock are below young layers! -
It is difficult to determine the absolute age of a sedimentary rock because sedimentary rocks are made up of diverse particles that are all different ages. As a result radioactive dating can only determine the age of the particles, not the whole rock.
Stratigraphic position Age Dating techniques i.e. carbon etc Fossil Assemblage present in rock specimen
They studied fossils and applied the principle that old layers of rock are below young layers! -
In the cross section, examine the different layers. The layer at the very bottom will be the oldest, and the one above would be slightly newer, and the one above that even newer, and so on, until the most recent rock layer is found at the top. Therefore, the layer you study will depend on those features. If you know the age of one layer, you will know the relative age of another.
Radioactive dating is used to determine the absolute ages of rocks. By Jennifer Palos
Answer: The age of a rock compared to the ages of the rock layers.
Time