The timeline below represents time on Earth from the beginning of the Paleozoic Era (A) to the present (B). Which numbered position best represents the time when humans first appeared in the fossil record? The diagram below represents the placoderm fish Bothriolepis, an index fossil found in
New York State
.
Where are most index fossils found?
Because most fossil-bearing rocks formed in
the ocean
, the major index fossils are marine organisms. That being said, certain land organisms are useful in young rocks and specific regions.
Which fossil could be used as an index fossil?
In marine strata, index fossils that are commonly used include the
single-celled Protista with hard body parts and larger forms such as ammonoids
. In terrestrial sediments of the Cenozoic Era
Which location most likely contains the youngest fossil?
The oldest layers are on the bottom, and the youngest layers are
on the top
. Because sediments sometimes include once-living organisms, sedimentary rock often contains a lot of fossils. Fossils are once-living organisms that have been turned into rock, in which the shape or form of the organism can still be seen.
Which fossil would be the best index fossil?
Trilobites
serve as good index fossils, letting geologists date the age of the rocks that they are in.
How do you identify an index fossil?
Index fossil, any animal or plant preserved in the rock record of the Earth that
is characteristic of a particular span of geologic time or environment
. A useful index fossil must be distinctive or easily recognizable, abundant, and have a wide geographic distribution and a short range through time.
Will humans be a good index fossil?
Some fossils are more useful than others in establishing the age of rocks. These are called index fossils. …
It is possible that humans also will be good index fossils at some time in the distant future
. Humans have distinct hard parts, and we often bury our dead.
Which fossil layer is the oldest?
When a geologist studies 3 rock layers (and their fossils) there is the good chancce that the upper layer is the youngest and
the lowest layer
is the oldest.
Which fossil is the oldest?
Stromatolites
are the oldest known fossils, representing the beginning of life on Earth. “Old” is relative here at the Natural History Museum. In collections like Mammalogy or Herpetology, a 100-year-old specimen might seem really old. The La Brea Tar Pits have fossils that are between 10,000 and 50,000 years old.
Which two layers are most likely the same age?
All of the layers of rock
were deposited at about the same time and are about the same age. The oldest rock layer is found on top, and the younger layers are closer to the center of Earth.
What is a good example of an index fossil?
There are some types of index fossils which include
Ammonites, Brachiopods, Graptolites, Nanofossils and Trilobites
. Ammonites: The fossil of ancient marine animals is said to be known as an ammonite index fossil. During the Mesozoic era, they were common (245 to 65 million years ago ).
Which era is longest?
The longest timeframe officially designated as an era is
the Paleoproterozoic
Which of the following is the best example of an index fossil?
Of the following organisms, the best index fossils would be:
a specific type of trilobite that existed for only a short geologic time in widespread geographic areas
.
What is the most famous index fossil?
Graptolites
are important index fossils in the Silurian and Ordovician age. Ammonites are important index fossils for the Jurassic and Cretaceous era. Previously, especially macro fossils such as ammonites and graptolites were used. Nowadays, especially micro fossils such as conodonts and foraminifera are used.
What four characteristics are best for an index fossil to have?
A good index fossil is one with four characteristics:
it is distinctive, widespread, abundant, and limited in geologic time
. Because most fossil-bearing rocks formed in the ocean, the major index fossils are marine organisms. That being said, certain land organisms are useful in young rocks and specific regions.
How is an index fossil used to identify a time period?
Index fossils are used to define geological periods. These fossils can be defined as “commonly found, widely distributed fossils that are limited in time span.” If one finds an index fossil
in a given layer, then one has bounds on the age of the layer
. Using index fossils, the geological periods are defined.
