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Second day: Sunday 13.04.2025.
Stops 7-10. Breakfast at 7.30
AM. Leaving at 8 AM (1½ hour drive to the outcrop).
Below: Geological sketch-map and cross-section (black line) of
western Cuba with indication of stops.
Below: Geological map of Cuba (1:250000) with indication of stops.
Click here for a high-resolution version.
Click here for
legend.
Stop 7. Prehistoric Mural
and Viñales Stonehenge. 22°37'7.59"N, 83°44'20.80"W. Scenic
views. We won't get off here, we'll just look down from the
bus. Transfer to the next stop (40 min).
See
on 1:250K geologic map. See
on geologic sketch map.
See on Google Maps.
Mural at Valle de Dos Hermanas.
Tower karst mogote hills and carbonate breccia forming karstic pinnacles. Valle Dos Hermanas
Stop 8. Entronque Moncada
section: K-Pg boundary (1½ hour). 22°33'14.21"N, 83°50'42.66"W.
Transfer to the next
stop (1 hour).
See
on 1:250K geologic map. See
on geologic sketch map.
See on Google Maps.
The section along the road displays an excellent example of the Guaniguanico K-Pg boundary and early Tertiary deposits, representing the transition from ProtoCaribbean basin (Pons-Moncada-Ancón Fms) into the foredeep basin sediments (Manacas Fm).
The section overlies the Albian-Cenomanian well-bedded black micritic and biomicritic limestone with lens and irregular concretions of black cherts (Pons Fm). These limestones are separated by an erosional contact and a long hiatus from the K-Pg boundary Moncada Fm (an approximately 2-m-thick complex characterized by repetition of calcareous sandstone beds that show overall upward fining and thinning). The Moncada Formation contains abundant shocked quartz, altered vesicular impact-melt fragments, and altered and deformed greenish grains of possible impact glass origin. In addition, a high iridium (ca. 0.8 ppb) peak is identified at a clayish layer on top of the formation.
On top of the K-Pg boundary occurs the Paleocene to Middle Eocene section which consists of about 18 m of well-bedded, light reddish-violet-green micritic, slightly recrystalized to sublithographic limestone with interbedded shales of the Ancón Formation, which grades upward into shales and fine grained sandstones of the Pica Pica Mb of the Manacas Formation.
Type locality of the Moncada K-Pg boundary unit.
Left: Slaty violet limestone of the Paleocene Ancón Fm.
Right: Ancón Fm and the overlying Manacas Fm (Pica Pica Mb).
Stop 9. Manacas Formation
(1 hour).
22°34'58.47"N, 83°48'6.93"W. Transfer to the
next stop (20 min).
See
on 1:250K geologic map. See
on geologic sketch map.
See on Google Maps.
A small quarry on the south side of the Viñales-Moncada road exposes a deformed olistostrome (Vieja wildflysch) of the Manacas Formation. The olistostrome consists of a chaotic mix of clastic elements within a sandy-gravel, quartz-rich matrix. The proportion of the matrix and the composition of the clastic elements vary across different localities. The quarry contains clastic elements ranging from a few centimeters to 1-3 meters, composed of Mesozoic limestones and shales, deformed into slates and schists with a boudin-like shape and concentric foliation. The matrix constitutes a small part of the rock. The deformation likely relates to the detachment zones of thrust faults, with the Manacas Formation typically capping the stratigraphic sequence of each nappe, and underlying rocks showing no recrystallization.
Deformed foliated matrix of the Vieja Wildflysch (Olistostrome)
Subangular sandstone (left) and
limestone (right) blocks in deformed matrix.
Deformed lenticular blocks (boudine) in deformed matrix.
Stop 10. Ichthyosaur Cave.
22°36'30.02"N, 83°45'41.94"W.
See
on 1:250K geologic map. See
on geologic sketch map.
See on Google Maps.
The El Cuajaní is a beautiful small valley with very strong karst corrosion. The Late Tithonian El Americano member rocks here are represented by well-bedded black micritic and biomicritic limestones with lens and irregular concretions of black cherts. The partially articulated skeleton of an Ichthyosaur is exposed in the interior of the cave. Several samples recovered from the fossil-bearing slab contain a microfossil assemblage of the Tithonian Bonetilla boneti (or Boneti) Subzone, the upper part of the Chitinoidella Zone. The fossil bones are concentrated around the vertebral column, with a few ribs, isolated vertebrae, and one fin scattered nearby. The vertebral column is bent into a U-shape, with the caudal vertebrae positioned above the cervical vertebrae. Absent parts are the skull, girdle elements, both forefins, and one hindfin. The morphological pattern of the hindlimb resembles that of Late Jurassic Platypterygiinae ophthalmosaurids, such as Caypullisaurus bonapartei and Aegirosaurus leptospondylus (Iturralde-Vinent et al., in preparation) (2 hours). Transfer to Benito's tobacco house (30 min).
Fluvial cave entrance, just above present day river. Open in well bedded micrites and biomicrites of the El Americano Member. Collapsed blocks illustrate the high level of karstic evolution.
Left:
Ichthyosaurs hindfin. Right: Ichthyosaur vertebrae and ribs.
Stop at Tobacco plantation. Visit to a tobacco family-run business (Benito's tobacco house) near Viñales town to get an insight into the traditional way of making cigars from tobacco drying house and rolling demonstration. In addition, you can have the opportunity to smoke an organic Cuban cigar. If time allows visit to Viñales Town (free walk).
Benito’s son in the classic wooden house.
Organic natural products including handmade tobacco and free coffee.
Arriving at hotel Rancho San Vicente and casas
particulares in Viñales at ca. 6 PM. Dinner at 7 PM. 8.30 PM,
after dinner meeting to discuss the geology of the day.
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