POST-TERTIARY FOSSILIFEROUS DEPOSITS. 89 



The estuarine muds at the mouth of the South Esk are typical, and the following 

 series of deposits has been described by Dr. Howden •} 



"LA layer of unstratified Boulder Clay, of a red colour, lying on rocks polished 

 and grooved in a general direction of west to east, and containing the dressings 

 of these rocks and travelled boulders derived from rocks to the west of their present 

 position. 



" 2. Laminated dull red clay, forming a terrace forty feet above the level of the sea and 

 containing marine fossils of an Arctic type and small boulders (transported from great 

 distances) of rocks foreign to the district. 



"3. A layer of stratified sand and gravel covering the laminated and boulder clay to 

 100 feet above the sea-level, identical in its mineral contents with the unstratified 

 moraine-gravels of Glen Clova. 



"4. Peat found in old water-courses, resting on the marine clay or on the gravel. 



" 5. A great bar of boulders stretching across the estuary mouth, derived apparently 

 from the Boulder Clay. 



" 6. A deposit of estuary or Carse clay and sand, extending to about fifteen feet above 

 the sea-level, and containing in its lower portions estuary shells. 



"7. An accumulation of blown or drifted sand, forming the links on part of which 

 Montrose is built." 



Since these old estuarine deposits and raised beaches occur at almost any point 

 between a few feet above high-water mark and thirty feet, the amount of elevation of 

 the land during the period they represent (as we pointed out was the case also during 

 the glacial period) must have been very unequal. 



Mr. Jamieson states that the elevation of the old estuarine deposits becomes less as 

 we proceed from the Eirth of Eorth to Aberdeenshire,^ commencing at from twenty-five 

 to forty feet in the Carse clay of the Forth and continuing at that point to the estuary of 

 the Tay, but at the estuary of the Ythan being eight feet and at Aberdeen only just 

 above high-water mark. 



4. Paisley, Cardium edule Bed. 



The position of this bed has been previously described (p. 25). It was about 

 nine inches in thickness and covered with four feet of surface soil. Immediately 

 beneath it was the Arctic shell-clay, in the upper part containing few fossils, in the 

 lower part an abundant fauna, with Cyprina Islandica as the characteristic species. 



' 'Trans. Ed. Geol. Soc.,' 1867-68. 



2 'Journal Geol. Soc.,' 1865, vol. xxi, p. 189. 



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