What percentage of rocks within Earth's history are almost completely devoid of fossils?

Answer:the Precambrian, more than 80 Percent. 88 percent to be precise.

Explanation:

Precambrian era existed since the creation of earth. That is, ''pre'' meaning 'before'' the Cambrian. The Cambrian period is about 541 million years ago.

All life-forms were long assumed to have originated in the Cambrian, hence, all the rocks earlier are grouped into Precambrians - completely devoid of fossils.

The Precambrian consist of the archean and the proterozoic eons which are geologic intervals that lasted for about four millions to about five-hundred and fourty-one millions years ago.

The Precambrian covers almost 90% of the entire history of the Earth. The Precambrian Era consist of all of the geologic time before six (6) million years ago (that is; like about 4.6 billion years ago).

Majority of the fossils in the Precambrian time are being stromatolites that is, they are often deeply buried.

88% of rocks are almost completely devoid of fossils

Explanation:

Precambrian era which means "Before the Cambrian period". Geologists have found that there are some hard to discern fossils in some Precambrian rocks. Precambrian covers almost 90% of the entire history of the Earth whereby 88% of rocks are almost completely devoid of fossils which has been divided into three eras: The Hadean, The Archean and The Proterozoic