Luz Beach (Lagos, Portugal) a unique place for an educational and touristic glimpse of the Geological Cycle and fossil record

1. Luz Beach (Lagos, Portugal)
a unique place for an educational and touristic glimpse of the
Geological Cycle and fossil record
Renato Godinho*, Nathalia Lima and Luís Azevedo Rodrigues
1 – 15 December, 2021
* rgodinho@lagos.cienciaviva.pt

2. 1. Geographic framework;
2. Geological framework;
3. A privileged place to teach geoscience;
4. Ponta da Calheta;
5. Cliffs;
6. Ponta das Ferrarias;
7. Conclusions.
Index

3. • Luz beach is located 5km west of Lagos, in the south portuguese zone called Algarve;
• It is one of the most famous beaches in this area, not only for the extensive sandy beach but also for the beauty of its cliffs;
• Wonderful colored cliffs cut by a black wall immediately suggest some geological variability.
1. Geographic framework
200km
P
O
R
T
U
G
A
L
SPAIN

4. • In the transition Jurassic/Cretaceous, the Algarve basin was subjected to strong tectonic tensions that caused a partition into
three domains: eastern, central and western;
• Luz beach is located on the western part of the basin, characterized by a deposition in a brackish lagoonal environment, near
to the coastline.
2. Geological framework
• Luz beach belongs to the Mesocenozoic
Algarve Basin, which extends from Cabo S.
Vicente in the west to the River Guadiana in
the east, formed during the opening of the
North Atlantic;
Adapted from Lopes (2006)

5. 3. A privileged place to teach geoscience

6. • In Ponta da Calheta a medium to fine sandstones could be observed, with parallel lamination and cross stratification
(hummocky structures), dated from Aptian;
4. Ponta da Calheta
• These beds contains very rich
levels of gastropod shells of
the genus Nerinella
algarbiensis, with a
preferential orientation of
their major axes around
N105ºE;
• The sedimentary structures
and the orientation of the
Nerinella algarbiensis suggest
that the sandstones were
deposited in a coastal marine
environment.

7. 5. Cliffs
• The cliffs on the east side of the beach shows a sedimentary succession of about 40 meters thick, dating from the Aptian to
Albian;
• This succession is composed of
several lithologies, which include
clays, marls, sandstones and
limestones belonging to the Luz
and Porto de Mós formations;
• These intercalations reflect sea
level variations during the
Cretaceous, indicating different
depositional environments.

8. 5. Cliffs – Luz Formation
• The base of the cliffs is composed by clays, marls, limestones and sanstones, with a multicolored beds, belonging to Luz
Formation;
• The color variation reflects the
various oxidation states of
chemical elements, as well as
the amount of incorporated
organic matter;
• This sucession suggest a
deposition in a restricted
lagoonal-brackish
environments with few open-
marine episodes.

9. 5. Cliffs – Dinosaur Footprints
• In this clay-marl succession, there are some more
hardness carbonated levels, that compose
benches that resist coastal erosion;
• On one of these benches, around 45 dinosaur
footprints were discovered (September 2021) by
Rodrigues and identified for the first time;
• These footprints, still under study, could
preliminary be attributed to sauropods (manus
and pes?) of at least 3 different sizes and will be
the first multi footprints discovery of these
dinosaurs in Algarve.

11. • On top of the multicolored clays and marls, there are
several tabular layers of coarse to fine grained sandstones;
• This levels presents cross and parallel stratification,
rich in decimetric to centimetric charcoalized woods
and plant fragments;
• The depositional environment of these beds is coastal
marine with continental influences.
5. Cliffs – Carbonized plants
1cm
1cm

12. • The limestone beds are rich in
gastropods, and presents
laminations, bored
hardground and fenestrae
structures;
• The structures and
paleontological contents
indicates a shallow-water
marine environment on a
carbonate platform.
• The top of the sedimentary sucession in Luz beach is composed by alternation of bioclastic limestone and marls, belonging to
the Porto de Mós Formation that dates from Aptian/Albian;
5. Cliffs – Porto de Mós Formation
Porto de Mós Fm.
Luz Fm.

13. 6. Ponta das Ferrarias – Volcanic Chimney
• At Ponta das Ferrarias, on the contact between Luz and Porto de Mós beaches, the sedimentary succession is abruptly
interrupted by an elliptic volcanic chimney;
• This volcanic event that dates from the
Campanian (72 to 75 My) is contemporary of
the Igneous Massif of Monchique;
• The volcanic rocks has a vesicular and
brechoid textures, with small geodes, clast of
volcanic and sedimentary rocks, being
classified as lamprophyre;
• It also contains a dike with N-S orientation
with a few meters thick.

14. 30m
Luz Beach
Porto de Mós
Beach
Ponta das Ferrarias
N

15. 6. Ponta das Ferrarias – Contact Metamorphism
• The contact between the Luz beach sedimentary succession and the
magmatic intrusion created a zone of metamorphism;
• This contact metamorphism caused a change in hardness and color on
the original sedimentary rocks;
• In the zone of contact metamorphism, fractures filled with minerals that
precipitated from fluid solutions are common.

16. 7. Conclusions
• Luz beach is a place of excellence in geosciences teaching, providing an experience to observe all the rock cycle lithologies, as
well in promoting geotourism.

17. 7. Conclusions
• The variety of colors observed in the sedimentary rocks along
Luz beach tell a story of constant environmental changes, with
sea level rises and falls;
• The paleoenvironmental changes are witnessed by the
paleontological richness, where marine fossils, dinosaur
footprints and charred plants are observed;
• These factors contribute for Luz beach to be the ideal place for
teaching geosciences, with excellent in situ observations of
lithological and paleontological variability.

18. Thank you for your
attention and we look
forward to your visit!