Does that rock have dip? No, this is not another food metaphor! Dip is a technical geologic term meaning the orientation of a rock layer in 3 dimensional space. This property has to do with both direction and magnitude of the angle that a rock layer slants away from that famous horizontal plane. The line that is created by the intersection of the horizontal plane and the dipping rock layer is known as the strike of the rock layer and is always at 90 degrees to the dip. Lost yet? Ok, lets try it another way. If you have a layer of rock that is “dipping” downward away from the horizontal, it has a dip. The dip will have a direction and an angle downward. The greatest downward angle is always the true dip. Any other angle is an “apparent” dip. Geologists describe the orientation of a rock layer by using strike and dip and when these attributes are applied to a geologic map, geologist can read what is going on with the attitude of rock layers.
We live on the northeastern edge of the Powder River sedimentary basin. On our side of the basin, the rocks usually dip to the west/southwest. That means rock layers dive mostly westward toward the thickest/deepest part of the basin but then flatten out and eventually reverse dip as you approach the Bighorn mountains. This draping of sediments filling the bowl of the basin is a classic geologic setting. Many ranges in the rocky mountains have a large basin on one side, or the other, or both sides. These large bowls fill rapidly with sediments washed down from the mountains. Another large basin near us is the huge Williston basin in Saskatchewan, North Dakota and eastern Montana. Most of these basins are heavily explored for oil and the Powder River Basin is no exception. Hydrocarbon deposits of oil and gas are found most typically in these kind of geologic settings. When you hear the word basin, think of dip because all the rock dip toward the center of the basin. Little wrinkles (local changes) in the dip usually creates a geologic structure that traps oil keeping it from moving elsewhere. Several of the oil fields around here are just wrinkles on the edge of the basin.
Oil, to accumulate, has to have a source rock, a path for the petroleum to migrate from the source rock, and a trap to capture the petroleum. Large sedimentary basins are good places to find all three of these requirements. The basin is full of organic material as a source, the sloping sandstones make a good path for the oil to travel and the traps are abundant. Fortunately for us, all these conditions occur frequently around here and we have income from the mineral richness of our region. Some of us are luckier than other and have active producing oil/gas wells on their land. My land had considerable oil production in the 1960’s which enabled the family who owned the ranch at the time to build one of the (at that time) largest buildings in Campbell county on the ranch. They used to have indoor roping competitions in it and is big enough to turn a pickup with a horse trailer attached around inside. It was built with oil money.
While the above discussion about oil and related natural gas is a passing discussion as the fields like Belle Creek are declining in productivity, I keep reminding you that geology has a really big effect on our live. The impending coal bed methane (CBM) development will have a tremendous impact on our communities. Keep your eyes to the newspapers and attend any public meetings to keep informed of this process. We will all be affected by CBM and it will happen. It is just a matter of if we are dips or not about it.
I guess it is. nice post, weird how I found this blog.