55 
ON THE EXTENT OF THE GAP BETWEEN CHALK 
AND EOCENE IN ENGLAND, AND ON SO-CALLED 
UPPER CRETACEOUS FLORAS. 
By JOHN STARK IE GARDNER, E.G.S. 
M OST of those possessing even but a superficial acquaintance 
with geology in England are aware that the Eocene 
strata in this country invariably rest, often conformably, upon 
the Chalk. Those who have collected fossils from the rocks 
above and below the Chalk are familiar with the complete 
change in the fauna belonging to each. The thoroughness of 
the change is recognised in the fact that from the Chalk down- 
wards the rocks are considered to bs Secondary ; while strata 
above the surface of the Chalk are recognised as Tertiary . Al- 
though frequently but a slightly eroded surface and a few 
water-worn flints actually separate them, a vast interval indeed 
separates them in geological time. So immense must the 
time have been, that strata 10,000 feet thick may have been 
accumulated in other parts of the world during its lapse. Few 
geologists, however, appear to have realised this possibility, and 
we therefore find, when beds unmistakably of this middle age 
are under examination, that the question as to whether they 
are of Cretaceous or Eocene age is hotly disputed. We also 
usually find that when there is any internal evidence of a bed, 
especially if containing plant remains, being older than the 
known Eocenes, it is at once stated to be contemporary with 
one or other of our Cretaceous formations, even when a com- 
parison of the fossils, especially of the plants, would point to 
the impossibility of such being the case. I will endeavour to 
make the magnitude of this gap apparent. 
The Eocenes are composed, without exception, of the compara- 
tively local deposits of shallow seas, estuaries, and rivers, even 
those most essentially marine in character containing evidence 
that land was not far distant. The Chalk which stratigraphi- 
cally precedes them, contrasts with them very strongly, being 
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