Depositional history The Lourinhã Formation is located within the
Lusitanian Basin, a mostly onshore North South orientated
rift basin within western Portugal, formed during the
Opening of the North Atlantic Ocean, with sediment deposition beginning during the
Late Triassic-
Early Jurassic. It primarily consists of
syn-rift near-coastal continental
siliciclastic sediments, with several marine
intercalations. The primary flow direction was North to South, originating from
Galicia and flowing between the Iberian landmass to the east and the now largely submerged
Berlengas horst, a north–south oriented
ridge, to the west. The Lourinha Formation is interpreted as being an island, separated by North America and the rest of Europe by marine barriers. The Paleoclimate is interpreted as being semi arid, with less than 50 cm of annual precipitation and an average annual temperature of 16 to 19 °C. The overlying and intefingering
Freixial Formation has been dated through magnetostratigraphy to 150.8 to 146.5 mya. Therefore, the age of the Lourinha formation is between 152.5 to 146.5 mya.
Praia da Amoreira-Porto Novo Member The Praia da Amoreira-Porto Novo Member is composed of the Praia de Amoreira Member, which consists of massive
mudrock-sand with metre thick sandstone
lenses, with massive mudrock with
calcrete. The overlying Porto Novo Mb. consists of massive bodies of sandstone, often
cross bedded. The
environment of deposition is interpreted as a
meandering fluvial system, while the Porto Novo Mb is interpreted as a
deltaic deposit. It is interpreted to be latest Kimmeridgian in age, and overlies the Consolacao Unit at the top of the
Aulacostephanus eudoxus ammonite zone. The Continental facies of the Porto Novo Member intersperse into the Praia Azul Member & they transition vertically and laterally into each other. At Vale Pombas at least 2 tongues of the Porto Novo Member are interspersed with 2 tongues of the Praia Azul Member. At Porto Dinheiro, the continental fluvial environment at the top of Porto Novo Member show tidal influence, evidence of interaction with the coastal ecosystem of the Praia Azul Member. In the region from Paimogo to Areia Branca the overlaying deposits of the Praia Azul Member correspond to the upper Porto Novo Member in that section, implying they intercalate. These details indicate the Praia Azul & Porto Novo Members represent laterally equivalent environments deposited simultaneously in adjacent, shifting, and laterally migrating sedimentary environments.
Praia Azul Member The Praia Azul Member, formerly known as the Sobral unit/member is 80 to 130 metres thick and consists of tabular
marls and
mudstones, with rare sandstones bodies. There are three distinct laterally extensive (>20 km) thin shelly
carbonate horizons within this member, indicating brief
marine transgressions. South of Santa Cruz primarily consists of sandstone with rare conglomerate. The age is considered to be latest Kimmeridgian to earliest Tithonian, correlated to the ammonite zones of
Hybonoticeras beckeri and
Hybonoticeras hybonotum.
Santa Rita Member + Assenta Member The Santa Rita Member in the Consolação sub-basin and its lateral equivalent in the Turcifal Basin the Assenta Member is around 300 metres thick and predominantly consists of mudstones with frequent layers of
caliche. Near the top of the member several layers of tens of metres thick
nodular and marly
bioclastic
limestones are present, containing marine benthic
forams, the nodularity is derived from intense
Thalassinoides burrowing. It is predominately Tithonian in age. The environment of deposition is interpreted as being an upper fluvial-dominated delta to meandering fluvial systems flowing on a
paralic plain. == Fauna ==