Verb Parallelism

The fossils preserved in the rock strata of the Grand Canyon have accumulated for a billion years and provide an invaluable geologic record.

I wonder why “provide” is not “provided”. I think “provide” has to be provided because there’s “and”. And the verb before “and” is “have provided”

I’ve been understood that a tense of the verb before “and” has to be the same tense as the verb after “and” Or it just has to be only the same type of speech not the same tense ?

In grammar, parallelism, also known as parallel structure or parallel construction, is a balance within one or more sentences of similar phrases or clauses that have the same grammatical structure.The application of parallelism affects readability and may make texts easier to process. Wikipedia

But it might help to note that parallelism is just a stylistic recommendation to make your writing easier to read -- not using parallelism is not ungrammatical.

In your particular example, as far as tenses go the parallelism is kept intact.

The fossils preserved in the rock strata of the Grand Canyon have accumulated for a billion years and provide an invaluable geologic record.

Both verbs are in the present tense. 'Have accumulated' is present tense in the perfect aspect while 'provide' is present tense in the simple aspect.

There's a good article here which explains the differences between tense and aspect.