Stratigraphy and dating
Environments and geological time
How do we place Angeac in time?
Dating a fossil deposit requires several lines of evidence. The position of strata, the fossils they contain and comparisons with other sites provide complementary information.
The method in practice
Stratigraphy studies the succession and relationships of strata. Biostratigraphy uses the distribution of fossil organisms through time. In continental and lagoon environments, pollen, charophytes and other microfossils help establish correlations where the usual marine markers are unavailable.
At Angeac and in regional comparisons
Angeac’s age has been revised. An initial assignment based on pollen and spores was reassessed using charophytes and vertebrates. Combined pollen, spore, charophyte and vertebrate evidence now places the deposit in the Berriasian, at the beginning of the Cretaceous.
What this research reveals
A facies describes a deposit type; it does not provide a date by itself. Likewise, the age of reworked sediment differs from that of a transported fossil. Recent research places the deposit in the Berriasian, at the beginning of the Cretaceous.
Examining the evidence
Comparing three sections of the deposit
Sections R3, CG3 and CG9 show the succession of clays and sands containing bones and fossil wood. Their correlation uses elevations in the NGF_IGN69 system. The boundary between units 1 and 2 provides a reference for measuring thicknesses.
The same height on the page does not necessarily mean the same elevation: first check the scales and correlation markers.
Specimens and data
Linking strata to depositional events
The composite log combines observations from several sections. In this diagram, the boundary between units 1 and 2 marks the base of the bone-bearing layer.
Enlarge each plate to examine labels, specimen identifiers and scale bars.
People and expertise
Pierre Hantzpergue’s work on stratigraphic successions and Roch-Alexandre Benoit’s work on charophytes offer complementary approaches to dating.
Further reading
Pollen and spores: reassessing age and environment — 2018 ↗
First characterisation of the Angeac deposit — 2012 ↗
Overview reference: Dinosaures, les géants du vignoble (2017), p. 30–35, 132–133, 152–155.
Publications and results → · The book and its authors →
Scientific research on this topic
- 2022 · Vertebrate diversity across the Jurassic–Cretaceous transition (article)
- 2018 · Pollen and spores: reassessing age and environment (article)
- 2017 · Charophytes of the northern Aquitaine Basin (article)
- 2017 · Palynological reassessment of Angeac sediments (conference contribution)
- 2012 · First characterisation of the Angeac deposit (article)
