50 HAYDEN : GEOLOGY OF THE PROVINCES OF TSANG AND 0. 
the underlying rocks to this sandstone is never particularly abrupt, 
for the limestones above the horizon of Orbitolites macropora 
are always more or less arenaceous, and in some instances 
contain bands of (rue sandstone. Although comparatively rapid, 
the change to shallow-water conditions must have, at least 
in the Tiina-Kampa dzong area, been gradual and there is 
no sign of unconformity. The absence of fossils in the sandstone 
combined vi'ith the absence of any marked stratigraphical break in the 
sequence thus makes it impossible to demarcate the boundary 
between Cretaceous and Tertiary, and the sandstone may belong 
to either one or the other, or indeed partly to both. In the pre- 
liminary note published in Records, G. S. I., Vol. XXXII, pt. 2, it 
was provisionally referred to the danian stage, ^ but the ambiguity 
connected with that term renders its use undesirable, while the 
interval between maestrichtian and eocene may possibly be entirely 
represented by the eighty feet or so of limestone and sandstone 
above the Lithothamnion limestone. 
The ferruginous sandstone is succeeded by a series of calcareous 
beds which are lithologically not unlike the 
Gastropod limestone. , , . r-. ,. , , ,i • i 
underlying bcarp hmestone, but at their base 
there is a more decidedly abrupt change from sandstone to limestone 
than has been observed at any part of the underlying beds. The sand- 
stone passes rapidly up into limestone which is at first thin-bedded 
but is subsequently a hard dark massive rock full of badly preserved 
casts of gastropods ; above this is a shaly foraminiferal limestone, 
which passes up into shale overlain by more massive limestone 
with Orbitolites. The whole of this series, together with some 
shale and flaggy sandstone which overlies the Orbitolites limestone, 
appears to be of Tertiary age. 
The only section that was examined in detail occurs in the hills 
behind Kampa dzong* : it is perhaps best seen in the gorge at about 
' p. 165. 
' A more complete section would probably be found at the Dzongbuk l-a (see 
below p. 56). 
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