Over the past decades, cyclostratigraphy has been used to refine the Cenozoic timescale, and evidence for astronomical forcing of major climatic events has been identified in numerous records. Progress also has been made in the Mesozoic, although the absence of astronomical solutions complicates this effort. The next frontier for cyclostratigraphy is the Paleozoic. This talk will outline some of the challenges of cyclostratigraphy in deep time, using examples from the Late Devonian of the German Rhenish Massif. The Late Devonian saw repeated occurrences of widespread anoxia, some of which were associated with mass extinctions. The recurrent nature of these anoxic events suggests that astronomical forcing could have played a role in their initiation. Investigating this hypothesis requires an integrated stratigraphic approach. The cyclic deep-marine successions of the Rhenish Massif have been studied for over a century. This research history has culminated in many well-described outcrops with detailed litho-, bio-, and chemostratigraphy, ideal for cyclostratigraphy. Analysis of three sections that record the Kellwasser, Annulata, Dasberg, and Hangenberg biotic crises supports the hypothesis that these events were at least partially controlled by astronomical forcing. Furthermore, we show that cyclostratigraphy can be used to refine the Devonian timescale – if a consensus based on astrochronologies from various sites can be reached. With more and more cyclostratigraphic works being published, an astrochronological framework for the Late Devonian is starting to emerge, and the Rhenish Massif will be a key region to further develop this framework in the coming years.

Recent studies on the oldest sedimentary units of Saxo-Thuringia, comprising Neoproterozoic greywackes and Upper Cambrian–Lower Ordovician siliciclastic rocks, have demonstrated the necessity of reassessing the stratigraphic affiliation of certain units. In this context, it was first revealed that some Ordovician units had previously been erroneously assigned a Neoproterozoic age. A multi-method approach was applied to develop specific differentiation criteria based on petrographic, (isoptope-)geochemical and detrital zircon characteristics, which enable reliable differentiation between these units. Compared to the immature greywackes, the Lower Palaeozoic units are distinguished by a considerably increased maturity, which is manifest petrographically through the absence of feldspar and an elevated quartz content. Geochemically, the increased maturity of Upper Cambrian–Lower Ordovician units is further reflected by higher SiO₂, accompanied by significantly lower Al₂O₃, Na and Ca contents. The Lower Palaeozoic units can also unequivocally be distinguished from the older greywackes in terms of isotope geochemistry, due to their significantly higher ⁸⁷Rb/⁸⁶Sr ratios of >4. These characteristics are derived from the intensive weathering phase occurring during the Cambrian Period, which led to the reworking and resedimentation of the Neoproterozoic clastic material. The youngest detrital zircon U–Pb ages established an Upper Cambrian–Lower Ordovician maximum age for the Clanzschwitz Group (North Saxon Block) and the Seidewitz Formation (Elbe Zone), contrary to the previously assumed Neoproterozoic age of sedimentation.

Geoscientists documented the Great Ordovician Biodiversification Event (GOBE) within various clades. This has led to a discussion of mechanisms controlling the ecosystem changes that pushed a distinct Darriwilian peak in global biodiversity. A complex interplay of factors such as the highest dispersal of continental plates and the largest tropical shelf areas during the Palaeozoic, a very intense volcanic activity, extra-terrestrial dust input related to an asteroid breakup (L-chondrite parent body, LCPB), increased faunal interactions and competition in complex ecosystems presumably played a major role. However, scientists widely agree that global climate cooling was probably the major trigger for the GOBE.

Our high resolution δ¹⁸O and δ ¹³C study together with a bed-by-bed appraisal of conodont species richness in the Hällekis quarry at Kinnekulle (southern Sweden), displays a rising curve up through the Lenodus antivariabilis conodont zone (CZ). This is followed by a peak in the lowermost Lenodus variabilis CZ a plateau and a two-phased drop in richness in the upper variabilis CZ. Our δ¹⁸O record supports the results of a microfacies-derived sea level curve, indicating that the studied interval was mainly deposited during colder climates. The richness plateau and extinction pulse occurred when sea level was at its lowest. The suggestion that the LCPB disruption caused an enhanced flux of micro-meteorites to Earth around 467 Ma, triggering climate cooling and intensifying the GOBE, is heavily debated since the inferred LCPB level occurs within an overall period of cooling.

Biostratigraphy explores the distribution of fossils in time and space to identify intervals that can be correlated regionally/globally. The time resolution of Devonian ammonoid biozones varies between 200 Ka (upper Givetian) and >2 Ma (middle Eifelian). Precision for zone bases and tops is shorter. Due to complex environments, the nature of biozones is also complex, which is not visible in common biozone terminology. Marine animal ranges are in general affected by sea-level, condensations, facies shifts, and sedimentary gaps. Despite their open shelf, pelagic lifestyle, even ammonoids were highly facies-sensitive. Different zone types are proposed:

Global Phylozones are defined by speciations and FADs (first appearances) within non-endemic, branching lineages, suggesting changes in pantropical populations (middle Frasnian Beloceratidae). Endemozones are defined by the FADs of endemic taxa (regionally different Famennian Prolobitidae). Migrozones reflect sudden immigrations of lineages that have a longer evolutionary history elsewhere (Triainoceratidae in Europe-North Africa-North America). Cryptozones are defined by the sudden spread of taxa with unknown ancestry (Frasnian Devonopronoritidae in the Altai Mts. and Iran). Ecozones include epiboles (population bursts) in wide-spread event beds (“Archoceras” in Upper Kellwasser Beds). Desaster zones can be recognized after major extinctions by blooms of opportunistic survivors (e.g. Postclymenia Zone after the Hangenberg Extinction). LAD zones follow small-scale disappearances of index taxa (e.g. upper Anarcestes Zone in the upper Emsian).

Internationally, the best correlation is achieved using genozones, with FADs of index genera (or genus groups) but different oldest species in different regions. This implies a mixture of phylogeny and migration.

The present-day Middle Magdalena Valley, Eastern Cordillera, and Llanos Basin were once part of a large, multiphase basin system that began as an extensional basin during the Late Triassic–Early Jurassic and evolved into a retroarc foreland basin by the Late Cretaceous. By the late Eocene, this system was segmented into hinterland and foreland basins. Although the tectonostratigraphic evolution of these transitions is well understood, the basin architecture during each phase has not been fully reconstructed. In this study, we integrate stratigraphic and chronostratigraphic data from these basins and adjacent areas to develop a comprehensive regional framework. This correlation enabled the identification and mapping of Late Campanian and Maastrichtian maximum flooding surfaces, associated with the back-arc and retroarc foreland basin stages. Tracing these surfaces from the Llanos Basin to the Middle Magdalena Valley allows reconstruction of the basin’s spatial configuration through each tectonic phase. Our results document how basin architecture evolved in response to northeastward orogenic loading and the development of intrabasin structural highs, which led to localized erosion and non-deposition during the Campanian–Maastrichtian. These insights are critical for predicting the distribution and preservation of Lower Cretaceous marine deposits, which represent significant hydrocarbon source rocks. Additionally, we assess whether Maastrichtian sediment load and burial conditions were sufficient to trigger hydrocarbon generation in these source units, using the maximum flooding surfaces as chronostratigraphic markers.