Assessing the temporal patterns of mid-Cretaceous floral change in Portugal : a palynological and chemostratigraphic approach

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Customised display of large mineralogical (XRD) data: Geological advantages and applications

X-ray diffraction mineralogical analysis of geological sequences is a well-established procedure in both academia and industry, rendering a large volume of data in short-analytical time. Yet, standard data treatment and resulting interpretations present limitations related to the inherent complexities of natural geological materials (e.g. compositional variety, structural ordering), and are often time consuming and focussed on a very detailed inspection. Several alternatives were evaluated in terms of advantages and disadvantages to the main goal of generating a user-friendly, fast and intuitive way of processing a large volume of X-ray diffraction data. The potential of using raw X-ray diffraction data to interpret mineralogical diversity and relative phase abundances along sedimentary successions is explored here. A Python based program was tailored to assist in raw data organisation. After this automated step, a 3D surface computation renders the final result within minutes. This single-image representation can also be integrated with complementary information (sedimentary logs or other features of interest) for contrast and/or comparison in multi-proxy studies. The proposed approach was tested on a set of 81 bulk and clay-fraction diffractograms (intensity in counts per second—cps and respective angle—º2Ɵ) obtained from a Cenomanian mixed carbonate–siliciclastic stratigraphic succession, here explored by combining mineralogical (XY) and stratigraphic/geological information (Z). The main goal is to bypass preliminary data treatment, avoid time-consuming interpretation and unintended, but common, user-induced bias. Advantages of 3D modelling include fast processing and single-image solutions for large volumes of XRD data, combining mineralogical and stratigraphic information. This representation adds value by incorporating field (stratigraphic/sedimentological) information that complements and contextualises obtained mineralogical data. Limitations of using raw intensity data were evaluated by comparison with the results obtained via other standard data interpretation methods (e.g. semi-quantitative estimation). A visual and statistical contrast comparison confirmed a good equilibrium between computation speed and precision/utility of the final output. © 2022 The Authors. The Depositional Record published by John Wiley & Sons Ltd on behalf of International Association of Sedimentologists

Albian angiosperm pollen from shallow marine strata in the Lusitanian Basin, Portugal

The evolution of angiosperms significantly changed the composition of the terrestrial vegetation during the mid-Cretaceous. In contrast to the wealth of information available on the biology and systematic relationships of early angiosperms, the temporal patterns of their evolution and radiation are poorly constrained. Here we present a continuous angiosperm pollen record from well-dated shallow marine deposits in the Lusitanian Basin, Portugal. The São Julião section provides a solid stratigraphic framework to track angiosperm pollen distribution patterns from the early Albian to early Cenomanian at mid-latitudes. In comparison to previous angiosperm pollen records from the Lusitanian basin, the section shows an extended late Albian succession and provides new insights into the diversification of early angiosperms during this important interval. Productive palynological samples were analysed and 79 different angiosperm pollen types have been recorded. Throughout the Albian angiosperm pollen represent only a minor component of the total palynoflora. The early Albian pollen record is characterized by highly diverse assemblages of monoaperturate pollen of monocot or “magnoliid” affinity and by the first appearance of polyporate and tricolpate pollen of eudicot affinity. A distinct diversification phase among tri- and poly-aperturate pollen (e.g., Cretacaeiporites, Retitrescolpites, Rousea, Striatopollis and Tricolpites) and the presence of conspicuous pollen grains assigned to Dichastopollenites characterize the middle and late Albian palynological assemblages. Thus, the section records a striking sequence of appearances of important angiosperm pollen morphologies. Monocolpates, polyporates and tricolpates appear in the early Albian whereas tricolporates appear from the early part of the late Albian onwards. Furthermore, well-constrained biostratigraphic ranges of selected angiosperm pollen from mid-latitudes are presented. In view of these new data, the temporal framework of the palynological Subzones II-B and II-C in the Potomac Group succession from the Atlantic Coastal Plain, eastern USA is revised to a middle to late Albian age