How much do you think tectonic forces may have contributed to thermal maturity? In the Bakken we’re generally somewhere between 9000 and 11000 ft., but there just hasn’t been the amount of deformational influence I’d expect in the Monterey. Heat flow might be a bit different, there, too. As a result, I’d expect the sweet spot to be a mite shallower.
The Williston is a cratonic basin and the Gulf Basin is what is known as a passive margin. Both are known for having low heat flow. I would think that California would have higher heat flow with all the basement rock nearby. So, 10,000’ may be too deep. But, my knowledge of California geology is pretty limited. A quick search of some geochemical papers would provide an answer.