44 - 1 DONALD C. BARTON 



deposits would probably be indistinguishable from the correspond- 

 ing types of deposits of the temperate zone. No deposits have been 

 recognized to be of this type. 



i. Terrestrial. — (a) Deposits laid down under semi-arid condi- 

 tions: Arkose reddish, composed of subangular iron-stained grains 

 of quartz and partially decomposed feldspar deeply in an iron- 

 stained matrix of line-grained quartz and of argillaceous material. 



When the moist temperate conditions give way to those of 

 aridity, the mantle of vegetation, weakened by the change, is 

 no longer able to protect the accumulated products of decomposi- 

 tion and disintegration, and during the occasional violent storms 

 they are quickly eroded, to be deposited with rapidity usually in 

 the near-by valleys and catchment basins. Owing to deposition 

 from torrential streams, the materials of the mantle of disintegrated 

 material are laid down in coarsely stratified banks and lenses of 

 arkose. showing much foreset and cut-and-hll cross-bedding. The 

 soil and mantle of completely decomposed rock are deposited, 

 partially sorted, as cross-bedded, argillaceous sandstones and as 

 more finely and evenly stratified gritty muds tones. As the 

 temporary lakes dry up, these mud beds become sun-baked and 

 glazed and cracked and may receive raindrop prints. Under the 

 conditions of alternate wetness and dryness, there should be almost 

 complete decomposition of organic matter and oxidation of the 

 iron. 



Deposits of this type are not rare, and a good example ma}- be 

 found in the Sugarloaf arkose of the Connecticut River Triassic. 

 The formation occurs in what was possibly a Triassic basin, and 

 consists essentially of an unordered alternation and repetition of 

 gritty, argillaceous sandstones, conglomerates, arkose. and sandy 

 and calcareous mudstones. There is a coarse, general stratification 

 whose dip initially was apparently low. In the beds of mudstone. 

 even, line stratification is the rule, but cut-and-hll bedding is found 

 in a few places. The coarser strata are strongly cross-bedded, 

 mostly with the foreset type of bedding. Cut-and-hll bedding, 

 however, is common. The mudstones show mud-cracks, raindrop 

 prints, glazed surfaces, and reptile footprints. The arkose is 

 found in banks and lenses, chiefly at or near the base, but also at 



