A. Rk. Horwood—Upper Trias, Leicestershire. 365 
Trias not far from the delta-head, it would be natural to find at 
this point a considerable extent of blown sand and dunes at the bar 
of the delta. But the evidence is confined, in the Soar Valley, 
more or less to a level of 300 feet O.D. 
The sort of conditions prevailing then, locally, show that in 
Lower Keuper times the sediment which was detrital, laid down 
under estuarine conditions, thickened westward, and the waterstones 
and marls became transitional to the next phase (lacustrine). In 
the Red Marl phase calcareous strata thickened eastward, arenaceous 
westward, as in the Coal-measures according to a general law, but on 
the whole the sediments thin to the south-east, and were laid down 
under lake conditions, the river being gradually absorbed. Some 
agency contributed to the unsuitable state of the waters for organic 
life (sulphurous?), but at rare intervals some submerged land arose 
and animal and plant life were able to subsist for a time. Probably 
in this way the flora and fauna were markedly migratory. 
During the Rhetic phase in England (earlier on the Continent) 
initial marine conditions arose, and the Keuper waters gradually lost 
their distasteful character, though the stunted fauna at this time 
shows that there was a struggle for existence. The Triassic flora 
and fauna, as a whole, do not bear any resemblance to those of dry 
regions to-day, but rather resemble in composition those of the estuaries, 
swamps, and lagoons in and around the mouths of large rivers and 
their banks, which, again, have a direct communication with the sea. 
The Upper Carboniferous was a period during which the surface 
was depressed, with periodic elevations. During the Permian there. 
was depression for lacustrine and marine conditions, and elevation for 
the manifestation of volcanic activity. The Trias at its commence- 
ment was an elevated area, and there was a gradual submergence or 
subsidence up to Rhetic times with intervening oscillations and 
periodic elevation. The conditions may be summed up in tabular 
. form thus :— 
Bunter. River. Torrential or pluvial| N.W. Scotland, in 
fluviatile. Midlands, Lickey’s 
: Hartshill, etc. 
(quartzites, etc.). 
Lower Keuper. River. Formation of head | Millstone Grit, Coal- 
of delta and lagoons | measures, Permian. 
(estuarine). 
Upper Keuper. | River, merging | Lacustrine (waters | Granites and syenites 
into lake, with | sulphurous). of Midlands, Coal- 
overflow of silt. measures, Sand- 
stones, etc. 
Tea-creen Marl. ne a Estuarine and lacus- 
trine initially ma- Ditto. 
; : rine. 
Rheetic. Transition from | Initial marine phase. | Ditto, Coal-measures, 
lake to sea. shales for . detrital 
matter, carbonate of 
lime from organisms. 
