[crusty old prospector]

Go down to any swamp in Louisiana or any other state and you will see coal forming. It is mostly the leaves from trees that are deposited and buried. First, peat then lignite then coal. You can still see the imprints of the leaves as lignite but by the time it converts to a coal, most of them have disappeared. The deeper the burial, the higher the grade, i.e. BTU value as what is left becomes increasingly higher in pure carbon and less water. So, why is coal formation any different than an oil source rock? Substitute algae in the oceans for the trees. There is an abundance of coal bed methane production in the Four Corners area and norther Alabama, just to name a few.

As an aside, the reason why the source rocks in many basins produce mostly gas and very little oil is that they are Type III kerogens, which is derived from terrestrial plants. Think of a big flood in the Mississippi River carrying all the plant debris out into the Gulf where it sinks to the bottom. Oil source rocks primarily are Type II kerogens while some freshwater lakes in the past in the Rockies areas for example have produced Type I kerogens, which has their own distinctive types of crude oils that result from them. I believe they tend to be very waxy.

[Dusty Road]

Crusty I don’t think people realize how much material settles to the ocean floor on a daily basis and how it builds up over time. Nor do they realize just how much of the world was covered in water. On the ranch we find saltwater oyster beds in layers deposited along the hill’s. I think we’re 2300 ft above sea level yet at one time we were the ocean floor.

[Cletus.D.Yokel]

Your example is localized.