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The Antiquity of Man

Charles Lyell, Sir · 1863 primary

passage 210 of 306 · Section of Alluvium of St. Acheul. > CHAPTER 17. -- POST-GLACIAL DISLOCATIONS AND FOLDINGS OF CRETACEOUS AND (3/6)

↪ you wandered here via “anticlinal synclinal flexures coal basins” — the connecting lines are tinted below

in brief
He details specific Moens Klint cliff sections (Figures 47-49), listing drift and till subdivisions, showing chalk and drift bent and fractured together, and citing Puggaard’s conclusions involving subsidence in shallow seas and floating ice deposition.

Number 5. Stratified sands and gravel, with occasionally large erratic blocks; the whole mass varying from 40 to 100 feet in thickness, but this only in a few spots.

The angularity of many of the blocks in Numbers 3 and 4, the glaciated surfaces of others, and the transportation from a distance attested by their crystalline nature, prove them to belong to the northern drift or glacial period.

It will be seen that the four subdivisions 2, 3, 4, and 5 begin to rise at B, Figure 47, and that at C, where the cliff is 180 feet high, there is a sharp flexure shared equally by the Chalk and the incumbent drift. Between D and G, Figure 48, we observe a great fracture in the rocks with synclinal and anticlinal folds, exhibited in cliffs nearly 300 feet high, the drift beds participating in all the bendings of the Chalk; that is to say, the three lower members of the drift, including Number 2, which, at the point S in this diagram, contains the shells of Recent species before alluded to.

Near the northern end of the Moens Klint, at a place called "Taler," more than 300 feet high, are seen similar folds, so sharp that there is an appearance of four distinct alternations of the glacial and Cretaceous formations in vertical or highly inclined beds; the Chalk at one point bending over so that the position of all the beds is reversed.

(FIGURE 49. POST-GLACIAL DISTURBANCES OF VERTICAL, FOLDED, AND SHIFTED STRATA OF CHALK AND DRIFT, IN THE DRONNINGESTOL, MOEN, HEIGHT 400 FEET (PUGGAARD).

  1. Chalk with flints.
  2. Marine stratified loam, lowest member of glacial formation.
  3. Blue clay or till, with erratic blocks unstratified.
  4. Yellow sandy till, with pebbles and glaciated boulders.
  5. Stratified sand and gravel with erratics.)

But the most wonderful shiftings and faultings of the beds are observable in the Dronningestol part of the same cliff, 400 feet in perpendicular height, where, as shown in Figure 49, the drift is thoroughly entangled and mixed up with the dislocated Chalk.

If we follow the lines of fault, we may see, says M. Puggaard, along the planes of contact of the shifted beds, the marks of polishing and rubbing which the Chalk flints have undergone, as have many stones in the gravel of the drift, and some of these have also been forced into the soft Chalk. The manner in which the top of some of the arches of bent Chalk have been cut off in this and several adjoining sections, attests the great denudation which accompanied the disturbances, portions of the bent strata having been removed, probably while they were emerging from beneath the sea.

M. Puggaard has deduced the following conclusions from his study of these cliffs.

First. The white Chalk, when it was still in horizontal stratification, but after it had suffered considerable denudation, subsided gradually, so that the lower beds of drift Number 2, with their littoral shells, were superimposed on the Chalk in a shallow sea.

Second. The overlying unstratified boulder clays 3 and 4 were thrown down in deeper water by the aid of floating ice coming from the north.

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topics: strata, rocks, and the geological record · volcanoes, earthquakes, and catastrophe

The Antiquity of Man · Charles Lyell, Sir · 1863