Cycles of Sedimentation vn the Hocene. 197 
The Tuffeau de Ciply is a sparingly fossiliferous lateral phase of the 
same bed, and is exposed in several places to the south of Mons. 
The continental Montian thickens eastwards from Mons, and consists 
of dark lagoon clays, fluviatile sands, and lacustrine limestones, with 
Chara and Physa. 
Landenian.—The Landenian consists chiefly of glauconitic sands, 
with some harder beds—calcareous or siliceous—of “ tuffeau”’, 
especially at the base. It can be separated into the same zones as in 
France, and the three zones demonstrate a marked transgression. 
During the time of deposition of the sediments of the zone of 
Cyprina Morrisi there seems to have existed in Eastern Belgium 
(Hesbaye) an isolated basin or tranquil gulf. In this area was laid 
down a basal sand (Sable d’Orp-le-Grand) followed by a considerable 
thickness of white chalky marl (Marne de Gelinden) with Cyprina 
Morrisi and numerous well-preserved plant remains. This is the 
“ Heersian”’ of the older Belgian writers. The waters of the main 
Anglo-Franco-Belgian Basin invaded this area at a later date, and 
one finds the tuffeau with Pholadomya Konincki resting irregularly 
on the Marne de Gelinden. 
The marine Landenian sands become less glauconitic ¥n the upper 
part and frequently pass up into false-bedded and lignitiferous 
fluviatile sands. As one approaches the Ardennes one finds that 
these continental deposits occur as narrow bands filling river channels 
in the marine beds or even in the Chalk. As a rule the streams seem 
to have flowed from south-east to north-west, and point to a small 
quantity of sediment having been derived from this direction. As 
one would expect, the continental Landenian is of very local 
occurrence. Towards the north-west, as borings in the neighbour- 
hood of Ostend have shown, estuarine clays of Woolwich type are 
present. 
Y presian.—As in the London Basin the Ypresian consists of a thick 
mass of clay (Argile des Flandres). There is a thin sandy basement 
bed and a line of pebbles at the base. The clay passes up into a very 
fine sand with Nummulites planulatus—elegans (Sables de Mons-en- 
Pévéle). Traced eastwards the clay grades laterally into more sandy 
littoral beds. The character of the latter demonstrates the tranquil 
conditions prevailing along the eastern shore of the basin. More to 
the north-west in the Flanders plain the main mass of the Ypresian 
clay passes up into sandy clays with beds of very fine sand, followed 
by more clay. Then follows a series of coarse elauconitic sands— 
the “ Paniselian”. For the French geologists the “ Paniselian ”’ 
commences with the coarse sands (Paniselian of Cassel), but the 
Belgian geologists include the sandy clays and fine sands below in 
this stage. The coarse glauconitic sands which make up the bulk 
of the “Paniselian” occupy the higher parts of the hills from Cassel, 
in France, to the River Senne, north and south of Brussels. Over a 
considerable portion of this area there is a thin band of clay at the 
base. This is the P1m of the Belgian Geological Survey. 
