This is probably in part the result of erosion of previously deposited sediments and sedimentary rocks along the unconformities and in part the result of ground-water cementation during periods of emergence.
Deposition on the shelf was interrupted by several marine regressions which produced unconformities in the stratigraphic sequence.
Heretofore former land periods were recognized by unconformities and the amount of time by the degree of change in the fossils, but now the amount of time is estimated in existing land surfaces by topographic forms alone.
From the earliest times of geologic study there have been observed unconformities of the strata and corresponding changes in the fossil contents.
Some of these unconformities are local and the changes of organic forms inconsiderable, but sometimes they are of wider extent and the changes of life system greater.
It is largely by means of unconformities that we read the history of mountain making and other deformations and movements of the crust.
Pre-Cambrian time probably was longer than all later geological time down to the present, as we may infer from the vast thicknesses of its rocks and the unconformities which part them.
We speak of the lost intervals represented by stratigraphic breaks or unconformities and commonly emphasize our ignorance concerning them.
View of the North Wall of the Grand Canyon of the Colorado River, Arizona, showing the Unconformities illustrated in Figure 207] How did the surface mm' come to receive its cover of sandstones b?
Which formations, if any, are separated by unconformities (51-53)?
These unconformities may also be closely simulated by structures produced in very different manner.
The association of conglomerates with unconformities is indeed so frequent that its possible occurrence will always be suspected and sought by the geologist.
These were the cause of the unconformities and the corresponding apparent wholesale changes in species so common in the rocky strata, and which gave rise to the doctrine of catastrophism of the early geologists.
Abundant evidence of this was supposed to be found in the unconformities so frequent in the stratified series.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "unconformities" in a variety of sentences. We hope that you will now be able to make sentences using this word.
