Oncolitic deposits (F1) of the facies subassociation A1 are interpreted as deposited in subtidal oncoid
shoals which migrated in a carbonate platform and under normal marine salinity waters, due to their fossil
In the transition zone, 1 to 3 cm of oncoid
packstone grade up into coarser microhermal packstone.
At the lamproite-oncolitic limestone contact, all the sparitic cement and the oncoid
edges were re-emplaced by a new generation of carbonate crystals (Fig.
reach up 15 mm size with a poorly to unlaminated spongy micritic cortex.
This lithosome layer, up to 2 m thick, was topped by concentrically laminated spherical oncoid
levels (delicate shrublike layers).
1991), which can contain abundant oncoids
and stromatoporoids (Labechia) up to 1 m in diameter (Fig.
They exhibit stromatolitic, microphytic thrombolytic facies with sedimentary fills, oncoids
, oncolites, pesoids, lithoclasts and intraclasts.
The one-meter tall stromatolites are marine in form, occur immediately adjacent to shore rather than in deeper water, are covered by a peat and soil with inter-head areas filled with a complex stratigraphy, are colonized by living freshwater mussels on their sides, appear to rim cenotes, and have oncoids
in the sand flats surrounding the field.
, as large as 2 cm, typically have a bryozoan, stromatoporoid or brachiopod shell fragment as nucleus, encrusted with Girvanella and Rothpletzella.
with tubular structure as fine micrite precipitated on filaments (calcified filaments) are seen (Fig.
Towards the eastern part of the section, it grades into 10 to 20 cm thick beds characterized by better sorting and a decreasing proportion of oncoids
and micritic matrix (Fig.