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3.1 Stratigraphy of the Curfs quarry
The stratigraphy of Jagt & Felder, 1996 was used
for orientation in the field and for this description of the stratigraphy.
In the base of the quarry the top of the Maastricht formation
(Felder partition IV) is exposed. The Maastricht formation is topped
by the Vroenhoven horizon, where the lower part of the Houthem
formation (V) begins with the Geulhem member. Until 1996,
the K/T boundary was traditionally placed at the Vroenhoven horizon,
but recent investigations (Smit & Brinkhuis, 1996) suggest that
the K/T boundary should probably be placed at the top (see also
8.4
Final conclusion) of the Berg en Terblijt hardground
(Base IVf-7).
The whole IVf7 section consists of alternating carbonates
occasional thin clay layers. From the base to the Berg en Terblijt
hardground the section consists of homogeneous calcarenites(suggesting
strong bioturbation). These calcarenitic layers are alternating
with discontinuous hardgrounds, overlain by graded fining upward
calcarenitic bioclast grit layers. The hardgrounds contain borings
and have encrustations. For detailed discussion about the hardgrounds
and bioclast grit layers, see 5
Bioclast grit layers and hardgrounds.
The interval of the section between the Berg en
Terblijt hardground and the Vroenhoven horizon is clearly
bedded. The irregular surface of the Berg en Terblijt hardground
is topped by a fining upward grading bioclast grit layer. At 25
to 50 centimeters from the top of the Berg en Terblijt hardground,
a thin clay layer (to 2 cm.) is found in the eastern part of the
Curfs quarry. This claylayer has variing thickness and is not continuous.
The only other place in the region known to contain these claylayers
is the Geulhemmerberg (Roep & Smit, 1996). In the Geulhemmerberg
multiple claylayers are exposed in infilled channels. From the Vroenhoven
horizon upward, the deposits are strongly bioturbated and thinner
bedded (Roep & Smit, 1996). The Maastricht formation
is deposited in a shallow, (sub) tropical sea (Smit & Brinkhuis,
1996).
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