Holbrook earned a bachelor's degree from the University of Kentucky, a master's degree from the University of New Mexico and a doctoral degree from Indiana University. He is a registered professional geologist in the State of Missouri.

The Missouri Board of Geologist Registration protects the public from incompetence, misconduct, gross negligence, fraud, misrepresentation or dishonesty; licenses only "qualified" professionals by examination and evaluation of minimum competence; enforces standards by implementing legislation and administrative rules and encourages development and partnerships with existing small businesses.

Holbrook replaces Thomas Watkins, who resigned.