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Overthrust in the Rockies and the Appalachians

Copyright 2003 G.R. Morton. This can be freely distributed so long as no changes are made and no charges are made. (

This is a picture I took of a seismic line on a poster at the Soc. Exploration Geophysicists convention. The line is from the Rocky Mountains. The picture is fuzzy, but one can clearly see that the strata is not continuous and has clearly been overthrust over itself. The sediment had to be deposited first, the rocks hardened and then the thrusting. The reason we know this is because of the parallel bedding on the upper fault plate. This takes time.

Below is a thrust from the southern Appalachians which presents real problems for the concept of a global flood.

From A. W. Bally, Seismic Expression of Structural Styles, AAPG.

The line was one shot by Texaco along the Alabama/Mississippi border just NE of Meridian, Mississippi. The reference is A. W. Bally, _Seismic Expression of Structural Styles, Vol. 3, AAPG Studies in Geology Series, #15,, p. 3.4.1-82. It shows a wonderful example of why slow sedimentation must be the rule and presents a big problem for the global flood. I apologize for the size (418 kb) but it was necessary in order to show the detail I wanted to show. A word about seismic. The black peaks and grey troughs are the reflections of sound off of various rock layers which are in the earth. By reflecting the sound, we can produce a picture, like this, of what the earth looks like under one's feet. The picture is about 20 km of seismic data. It can be seen that the valley in the unconformity is about 3 km wide. The thrust block is about 16 km or 9 miles long.

At the top of the section are the sediments of the Atlantic coastal plains. They are flatish-lying dipping slightly to the SE. They are about 3500 feet thick and consist mostly of sands and shales. They lie on top of a major unconformity which separates the Paleozoic Appalachian sediments from the Atlantic Coastal plain sediments. Below the unconformity is the Paleozoic sediments which consist not only of sands and shales but also very thick piles of carbonate and dolomite. They are around 18,500 feet thick. This is determined by the velocity of sound in those sediments. Rocks in the Paleozoic are almost always faster than rocks in the younger Mesozoic and Mesozoic rocks in general are even faster than those from the Tertiary.

If you look below the unconformity you will find a thrust fault having thrusted the Paleozoic sediments over on top of themselves Bed a is marked on both sides of the thrust fault and one can clearly see that it is over thrusted on top of itself. The friction of the thrust plane against the upper part of the thrust caused the sediments to be folded. The fold was then eroded. Since bed A to the right is buried by 1.3 seconds of Paleozoic sediment (approximately 10,000 feet), yet it intersects the unconformity where it is covered by NO Paleozoic sediment, this means that 10,000 feet of sediment was eroded from the point marked ‘hill’. If you look at the sediments just under the unconformity on the right and move to the left you will see layer after layer erosionally truncated by the unconformity until you get to hill where bed A is at the surface of the unconformity.

Where I marked a hill, If you look at the unconformity, you will see that it drops down at that point. The flat reflectors above are clearly onlapping the unconformable surface against the hill. The valley was eroded into the underlying Paleozoic sediments PRIOR to the deposition of the Mesozoic sediment. If you look just to the right of the hill, under the word valley, above the unconformity you will see a black reflector which runs into the hill to the left and then into the unconformity on the right. The relationship between this reflector and the unconformity shows that the valley to the right of the hill was infilled in a rather gentle way otherwise the sediments would be chaotic. This valley was probably an arm of the ocean at one point because the sediments that fill it are marine as are all the Atlantic Coastal Plain sediments.

After the Mesozoic sediments were deposited, the entire area was slightly tilted to the SE.

The sequence of events cause great problems for the concept of a global flood. Global flood advocates always say that fossilization can only occur during catastrophic events such as the flood. Well there are fossiliferous Paleozoic sediments below the unconformity as well as above. Thus the flood advocate must hold that all the sediment in this picture is from the flood. This means that during the flood 18,500 feet of Paleozoic sediment must have been deposited. It must then have hardened. Why? Because of the way the thrusting deformed the rocks. This is not a soft-sediment type of deformation. The upper thrust block moved as a solid block. If the sediments had been soft, this couldn't have happened. Soft ooze and mush won't transmit forces for 9 miles. Assuming that the Paleozoic constituted half of the flood's time, then in 6 months we must deposit 18,500 feet of sediment. This is a rate of 102 feet per day. There are slow-moving invertebrate fossils at the bottom of the Appalachian Paleozoic as well as at the top. All sorts of stationary shell-fish are found throughout the Paleozoic strata. Why everything wasn't at the bottom of the pile, after deposition of the first 102 feet on the first day, I can't comprehend. A further problem is the burrows which are found throughout the entire 18,500 feet of sediment. One must have exceptionally rapid burrowers in order to thoroughly burrow 102 feet of strata a day. That is enough sediment to cover a 10 story building each day. Next time you drive down the road, look at a ten story building and imagine it covered in sediment in one day and thoroughly burrowed by thousands of animals. Burrowed in such a fashion where the excavated sediments make a pile around the burrow which are then covered by the next layer which is a different lithology.

After the deposition of 18,500 feet of strata, and it's hardening (it takes lots of time for shales to de-water, yet we see no mega water escape structures in this sedimentary pile either), we must then have the time to thrust the Paleozoic section creating huge mountains (the Appalachians). After this, we must have time for the erosion of 10,000 feet of HARDENED sediment, which then becomes the unconformity surface. Then we must cover, in a gentle way, the entire area with 3,500 feet of Mesozoic sediment. This is a rate of 19 feet a day assuming that the Mesozoic here represented 180 days of flood deposition. One could hardly say that 19 feet a day of sedimentation is ‘gentle’. 19 feet of sediment where I lived a few years ago would nearly cover my 2 story house.

don't see how to explain this in a global flood/young-earth scenario.

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