Staff at PetroStrat were asked to assist with some PhD research being undertaken through the University of Manchester where there was some significant uncertainty as to the precise ages of the outcrops that were being studied. Biostratigraphic analyses were therefore undertaken on 10 outcrop samples from the Talara Basin and we are delighted to say that the samples yielded, good age diagnostic data.
The results of these analyses have recently been included for publication in a paper for the journal Sedimentary Geology. Our staff members, Jenny and Sarah, who project managed this study for PetroStrat and who carried out the microfossil and palynological analyses, were delighted to be included as co-authors on the paper and were delighted to be able to assist in resolving the age uncertainty surrounding the formations involved in the study.
Read the full paper on Science Direct
Jorge A. Lajo-Yáñez, Stephen S. Flint, Rufus L. Brunt, Mads Huuse, Sarah R.A. Searle, Jenny M. Sheppard. Disentangling tectonic and eustatic controls on forearc basin stratigraphy, Talara Basin, Peru. Sedimentary Geology (2022).
Abstract
The controls on basin-fill stratigraphy such as sediment supply, climate, eustasy and tectonics are well understood in many basin types, but there are few examples documented from forearc basins. Traditional evolutionary models for forearc basins emphasise the importance of accretionary processes under a largely contractional tectonic regime. The Talara Basin of northwestern Peru preserves a lower Eocene stratigraphic record of dominantly extensional collapse tectonics punctuated by periods of uplift/contraction, driven by variability of the subduction process. The margin is dominated by subduction erosion and only minor accretion processes. In this geodynamic setting, we present for the first time a sedimentological and sequence stratigraphic model for the 350 m-thick fluvio-deltaic succession of the Pariñas Formation. Three depositional sequences are stacked into a highstand sequence set comprising proximal fluvial strata that correlate down dip into marginal marine and marine deposits. Syn-sedimentary normal faulting related to episodes of subduction erosion restricted much of the Pariñas to hanging-wall locations subject to minor-scale transgressions. The succession evolved from shelf-confined clinoforms to later basin margin scale clinoforms, related to long-term sea-level rise. The interaction of eustasy, sediment supply and episodes of subduction erosion are integrated into an evolutionary model that may have application in other non-accretionary forearc basins worldwide. Although the model shares characteristics with extensional models for rift basins, the episodic subduction-driven uplift events add another component of relative sea-level complexity.
