I have re-read this thread, and thought I'd add some new comments. First, I'll provide a photo of a fault in underlying rock, with horizontal Permian rock on top (Bear Island, Norway). The boundary between the two rock groups is the horizontal pink line; the fault in the lower rock group is the slanted pink line.
and cross section of that region, derived from additional data, indicating the newer, unfaulted strata overlying the older, faulted strata:
The difficulty about this kind of fault that is overlain by unfaulted rock is that the original fault must occur [sometime], then the rock must be weathered
and lowered below sea level again for the newer layers to be deposited upon it. Therefore, such a thing will typically be in the lower layers of an unconformity, as shown here.
Many unconformities involve more recent sediments upon precambrian rock. As John has pointed out, the older rock is, the more likely that it will have been buried deeply enough to metamorphose, and lose the structure of the sedimentary strata. Similarly, it would lose the cracks that mark faultlines.
The point here is that
there are examples of what you've expected to see--faults in lower strata that do not continue through upper strata.
Why don't we see this a lot? Usually because the faults we look at are
active faults which crack whatever rock lies upon them.
Here is another example of one of the types of things you've said should exist. This is a seismic image, rather than a photo of a cliff face, but it is just as valid. Perhaps it is more valid, since it hasn't been modified by erosion or by bulldozers.
Again, this is something we expect to see: an erosional surface that has had new rock sedimented upon it.
Now, after reading through the thread, I've seen a couple of comments that suggest common sense may be tricking us. John already addressed this, but I'll reiterate it in my way because it is important. Most strata form underwater. From the
sediment thickness map mentioned in the tectonics thread, we see that most of it is near the coastlines of continents. This is where we'd expect to find it, since much of it forms from erosional runoff. It is only after the continental margin is lifted up out of the water that these new sediment layers will be exposed and subject to new erosion.
What we see on land is, of course, strata that have been lifted up. Most formed underwater. While a world-wide flood would also cause strata to form underwater, the current pattern of offshore sedimentation also does the same thing.
However the YEC view seems to be that what is above sea level was always above sea level (with the exception of the Hydroplate movement creating higher mountains), while the geologists' view is that continents are not stable, but are moving around and bouncing up and down (albeit very slowly). One cannot understand current geological theory very well while holding the assumption that what is currently above sea level always was above sea level.
Rocks that are above sea level are subject to erosion, and only rarely to significant deposition. Surface rocks often get ground into soil, especially in regions with reasonable rainfall and plant growth. Therefore,
we don't expect to see new strata on top of existing, visible, strata above sea level. If we see them in the unsual situations in which they form, we don't think of them as strata, as I comment on below.
There are relatively few strata that are the result of on-land deposition. Again, John gave us links to many of them. They include the loess of the midwest east of the Mississippi--wind-blown dust from the ancient Mississippi flood plain, after it drained Lake Agassiz as the glaciers melted. As now, the prevailing winds were from the west, so the dust blew to the east. Most of it settled out in Illinois and Iowa, and relatively little made it to Indiana. Other on-land sediments include the volcanic ash falls and lava flows, and sand dunes. When we see these on the surface, as alluded to above, we don't think of them as strata--just as stuff on top of the strata. But, there are lithified sand dunes and many basalt strata that we have mentioned before. Unfortunately, most such on-land depositions are immediately subject to erosion. Unless they are lowered below sea level, covered, and lithified, there is not much likelihood that they will be preserved for eons. The strata that we do see from these kinds of depositions are the lucky few that did get lowered again, and that did get covered up, and that later were lifted again to where we can now see them.
One way to tell whether strata were formed on land or underwater is to look at the fossils they contain. T.rex fossils or other land-dwelling animals or plants pretty much indicate that this was land at the time, and not ocean. The sediment type (volcanic ash or a fine shale) indicates whether it could have been dry land (ash covers everything) or the shore of a river or lake, or perhaps a flood. If there are ripple marks with footprints, it was very shallow water, or even mud on the shore of a lake or river or sea after the shallow water receded. On the other hand, if there are fossils of marine organisms, it's pretty likely we're talking about sediments that formed underwater. If there are the burrows of small animals preserved in the rock, then the rock must have been in shallow water for a long enough time for worms or other sea animals to burrow into it.
When we find marine fossils in a lower layer, then terrestrial fossils in layers above them, then marine fossils in layers even farther up, and if the rock types are consistent with water/dry/water deposition, we pretty much have to conclude that we're looking at a place that was below water for a while, then above water, then below water again. Sometimes, we can account for this with sea-level changes, but other times, we have to imagine the continental edge raising and lowering due to tectonic influences.
Of course, it contradicts common sense to imagine the edges of continents bouncing up and down like this, to erode mountains, then dip their eroded surfaces back under water for new sediments to form, and then lift them up again. But, at a few cm per year, it only takes a few million years to do this. A few million years is a tiny percentage of the age of the earth, even if it is a mind-bogglingly long time for us.
I recall a woman who was on a fossil-collecting trip with me once, saying afterwards--with some awe--"how thin my life is." A human lifetime, measured in typical limestone or shale deposition, is but a very thin line.
It is this "very thin line" aspect that makes some people (see YEC's posts above) think that "polystrate fossils" prove the Flood was real. These are fossils that span several strata (hence the name poly-strate or poly-strata). These fossils don't prove the flood was world-wide; they merely show that rapid deposition can cover things, and that things that have been covered and are in anaerobic environments don't decay very fast, so additional deposition and compaction can build up multiple layers.
This raises another point: even for "uniformitarian" geology, different types of sediments build up at very different rates. Some are slow, some are rather quick, and others are nearly instantaneous if there is a local catastrophe.
So, to understand current geological thinking, one must have a sort of "mental movie" of continents bouncing up and down really slowly, usually as a result of crashing into each other really slowly, with sediment forming on the submerged parts fairly efficiently, but under some circumstances forming on land. We need to imagine the edges of plates that rub against one another creating strains and stresses, that are relieved by earthquakes as one chunk of rock slides past another. The slip zones, faults, have to choice but to break all the strata that are in those chunks of rocks--and once the break has occurred, it's a weak point at which new slips are likely to occur. To make those faults stop moving, the strain must be taken away--perhaps by the continents moving apart as they "bounce." To cover those faults with new sediment that is unbroken, the broken strata must be submerged again. For us to see them, they must be lifted up again and eroded, but fortuitously not broken at the site of the old fault line when the stresses and strains of uplift occur.
Why do we think we know this?
This is the critical question. I might turn your attention to the USGS publication DDS57 (digital data series, available in pdf
here), which presents the results of analyzing some 8000 or so cores taken from the eastern half of Montana by oil geologists. From this kind of thing, we know the extents and thicknesses of the strata, even if they are very far below the surface. From dating samples for which dating methods are applicable, we can infer the ages. From examining microfossils in the different strata, we can correlate these strata with others that have also been analyzed--and some of which are fortuitously overlain or underlain by strata that can be dated. The types of fossils and the types of rocks reveal the depositional environment--terrestrial, lacustrine, shallow marine, deep marine, etc.
What's left is for us to work out a model that would account for the findings. Now that we can watch (have watched) plate movements, and can apply ever-more sophisticated techniques (like those magnetic anomalies, which apply to basalt and granite on land as they do to sediments formed underwater), we can account for the lifting and falling by tectonics. The rest falls into place as normal sedimentation. To see this, however, it is necessary to suspend disbelief, and "try on for size" the inferred ages of the rocks, the significance of the fossils, the effects of tectonic movements. Whether we believe it or not, we can still ask if the whole story hangs together, and if the explanation fits the data.
It is extremely difficult to account for the global findings, or even the restricted findings that apply merely to the US, by a global flood. Surface rocks are too different (see
US geological map. which shows the surface rock groups) to have been laid down by a single flood only a few thousand years ago,
if our
predictions from the Flood Model are valid. Fossil organisms and fossil pollen grains and fossil spores are segregated by strata and geographically. And, we have those sediments that seem only to be able to form on land, sandwiched between sediments that seem only to be able to form under water--and these show up in different places at different ages.
Having rambled thus, I would ask:
What questions remain for uniformitarians?
We've addressed the questions in the IP, but if we have done so correctly, we have also generated many more questions than we started with. We may also have addressed those questions in ways that seem satisfactory to us, but not to others. What are the holes, the confusing bits, and the new questions?
