In geology, a key bed (syn marker bed) is a relatively thin layer of sedimentary
rock that is readily recognized on the basis of either its distinct
physical characteristics or fossil content and can be mapped over a very
large geographic area.[1]
As a result, a key bed is useful for correlating sequences of
sedimentary rocks over a large area. Typically, key beds were created as
the result of either instantaneous events or (geologically speaking)
very short episodes of the widespread deposition of a specific types of sediment. As the result, key beds often can be used for both mapping and correlating sedimentary rocks and dating them. Volcanic ash beds ( and bentonite beds) and impact spherule beds, and specific megaturbidites
are types of key beds created by instantaneous events. The widespread
accumulation of distinctive sediments over a geologically short period
of time have created key beds in the form of peat beds, coal beds, shell beds, marine bands, black in cyclothems, and oil shales. A well-known example of a key bed is the global layer of iridium-rich impact ejecta that marks the Cretaceous–Paleogene boundary (K–T boundary). Please let me know if it works.
Answer:
I am 100% sure it is the mudstone. I believe they are the oldest rock in existence.
Explanation:
The correct answer to this question is B. Some members of the Fugate family had a genetic condition called methemoglobinemia, that gave a blue color to their skin. The gene causing this disease is an autosomal recessive gene, so to have this condition you need to be homozygotes for this recessive gene. Gene flow was prevalent in the Fugate family since not all of the children had blue complexion, but only four of them. The three children that did not have blue complexion, had the dominant allele, probably through gene migration from another population nearby. Also, since it is easier nowadays to travel, two separate populations could meet more easily. This increases the incidence of gene flow and explains the reduction of the occurrence of the condition.
Answer:
Vascular seedless plants include the club mosses, ferns, whisk ferns, and horsetails.
Explanation:
