DETRITIC FORMAT IONS 71 
4 morainic matters. Somewhere in the sandstones and slates (pro- 
: bably more upward) Bodenbender has (1911) discovered badly 
preserved remains of plants, among which has been determined: 
a 
‘ Neuropteridium, sp.; Equisetites (?). 
This series of pale-coloured sediments is capped by an almost 
100 feet thick sheet of a peculiar chocolate-coloured, dense and 
unstratified rock, having the odour of humid clay. Microscopically 
the rock has been proved to be a pelitic tuff. Over this bed fol- 
lows in perfect conformity a mighty series of red and brown 
_ sandstones. 
There is no doubt about the pale-coloured sediments below the 
tuff layer as corresponding to the lower Gondwana, i. e. to the Talchir- 
Karharbari-horizons. 
A series of red and reddish brown sandstones of the coarse arcose 
types succeeds over the brown tuff sheet with perfect conformity, 
partly almost psephitically developed and consisting mostly of an- 
gular grains of red feldspar and milkwhite quartz. The upper strata 
are all darker coloured and capped with volcanic agglomerate and 
ash layers. 
To the south from the Cerro Villa Union rises, as has been men- 
tioned, the great upbend of the Cerro Bola, showing the same 
| sequence of strata, but without the crystalline basement exposed. 
The profile here, forming an abrupt wall toward the Guandacol 
valley, was studied by Bodenbender (1897 and 1911). In these 
lower Gondwana layers he discovered in a carbonaceous layer the 
following plant remains: 
Neuropteridium validum, Feistm.; Noeggerathiopsis, sp. 
To the east the Gondwana layers are concordantly overlaid with 
thaetic and younger formations, dipping towards the Pagancillo low- 
land [Bodenbender (1911)]. 
Turning back to the Cerro Villa Union it may be observed, that 
the strata, described in the profile of the Cerro Guandacol, run with 
