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the lower parts of the undulated structures. Both scour fills generally show the same sedimentological
characteristics with a higher concentration of coarser grains and rhodoliths at the bottom, and a fining
upward trend. Lamination is absent, making the scour fills displaying as a massive and structureless
facies.
Interpretation
The large scours are interpreted as eroded channels that incised the previously deposited calcarenite.
After that they were filled with massive deposits. Both the undulated lamination and smaller scour fills
are interpreted as scour and fill system. Undulated features are created in the transition between the
upper flow regime parallel lamination and the antidune bedforms, i.e. in high Froude number conditions.
If the energy increases even more, flow might become supercritical. The combination of bed load transport
and gravity effects causes the depositional system to erode itself, creating the scours. As a consequence
of the increased energy a hydraulic jump is likely formed. The eroded and transported sediments are
subsequently deposited in the scour, generating the fining upward sequence observed in the outcrops.
4.3.4 Tabular cross-stratification
Description
These deposits consist of up to two metre thick tabular cross bedded calcarenite bodies (figures 4.8c and
4.8d). Some foresets tend to onlap on their base, while others make a sharper angle. Another important
feature in some outcrops is the show cyclic behaviour regarding the deposition of laminae.
Interpretation
The large scale cross laminated bodies are interpreted as sub-tidal prograding dunes of fragmented
bioclastic material, with relatively low-energy conditions which would allow the preservation of a linear
dune crest (figures 4.1 and 4.6a). Palaeo-transport occurred in the direction of the highest dip angle,
corresponding to the foreset of a dune. The typical transport direction for these dunes as observed in the
field was south-southeast (figure 4.12).
4.3.5 Large scale foresets
Description
This type of sedimentary structure shows up to five metres high tangential-shaped dune foresets, with a
laminae thickness of on average 25 centimetres. The length of the foreset — of which probably only the
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