Maryland Geological Survey 127 



or flaky in form. The smaller sizes are translucent, of a humus-brown color, filled with 

 small opaque flakes and grains. They crush plastically but the crushed portion reveals 

 no new characters. 



Essentially they are probably true clay and their appearance is that of the greater 

 part of what is separated as clay. But it is important to know whether they are merely 

 undisintegrated portions of clay, or whether they are minute concretions. The flaky 

 form of many of them supports this latter hypothesis, suggesting their formation in 

 moulds such as the plant fragments might afford. For the present, however, the ques- 

 tion must remain undecided. 



(2) Heavy 



The heavy minerals are : 



Abundant. — Muscovite, chlorite, serpentine. 



Rarer. — Tourmaline, glauconite. garnet. 



Essentially the heavy portion is muscovite, with gome chlorite and serpentine, 

 tourmaline and garnet being exceedingly rare. Of glauconite there are very few grains, 

 many of them weathered yellow. 



//. Silt 



Dark dirty, brownish-black, micaceous. The dark color appears to be due mainly to 

 the great amount of black carbonaceous matter which is probably responsible for the 

 high percentage of silt separated from this sample, though the large proportion of the 

 finest-grained sands is probably also a factor in this result. The carbonaceous matter 

 not only contributes to the silt itself but also catches up many grains of fine sand which 

 are floated off with it. There is very little argillaceous matter and that in irregular 

 flocules, not in the rounded grains noted in the. very fine light portion. 



Summary and Conclusions. — Noteworthy are: 



(1) The very small proportion of sands and the large proportion of 

 clay. 



(2) The very high proportion of carbonaceous matter. 



(3) The granules of argillaceous matter and the pyrite concretions 

 as in sample 1. The sample seems to be, like sample 1, high in heavy 

 minerals, but this is deceptive since micas are the principal constituent of 

 the heavy portion, and these in spite of their specific gravity are classed, 

 in the processes of sedimentation, rather with the light and fine-grained 

 minerals. 



SAMPLES NO. 1 AND NO. 2 



General Summary and Conclusions. — While sample 2 is markedly dif- 

 ferent from sample 1 in the much lower percentage of sand, in the general 

 dominance of the fine-grained materials, and in the scarcity of heavy 

 minerals other than mica, it still has in common with it certain features 

 that are essential. Foremost among these is the wide range of size in the 

 sands; for while these are dominantly finer-grained they do not show that 

 dominance of any one size that is characteristic of the most typical marine 

 sediments which have been subjected to the sorting action of strong waves. 

 This is at once apparent from an inspection of the diagrams of these two 



