Regular stratigraphic alternations in lower Paleoproterozoic iron formations (IFs) from South-Africa and Western Australia were recently linked to Milankovitch forcing (1, 2). Hence, valuable information may potentially be obtained from these ancient marine deposits about early Solar System dynamics and astronomical-forced climate change when Earth System was operating in fundamentally different ways compared to present-day and the Phanerozoic. In particular, the dominant imprint of long-period eccentricity observed in the Kuruman IF from South-Africa (2) implied a primary influence of climatic precession, while clear precession-scale variations were unfortunately not encountered in this unit. A clear and consistent expression of precession and eccentricity, however, is essential to investigate the climatic-environmental response to the precessional forcing directly, and to determine the precession frequency as to potentially constrain past Earth-Moon dynamics. Here we report results of cyclostratigraphic analysis and high-precision U-Pb dating of the 2.46-Ga Joffre Member of the Brockman IF, Western Australia, revealing exceptionally regular precession- and eccentricity-scale alternations identified in both outcrop and core. Based on the thickness ratio between the precession- and short eccentricity-related alternations seen in outcrop, we estimate a significantly shorter precession period at the time of deposition of the Joffre Member, translating to a shorter Earth-Moon distance and length-of-day (3). In addition, based on detailed geochemical analysis and modelling of the precession-related cycles identified from core, we present a first-order climate interpretation with possible implications for the redox evolution of the ocean-atmosphere (4).

(1) de Oliveira Rodriguez et al. 2019; (2-4) Lantink et al. 2019; 2022; 2023.

This talk presents a multi-method approach to construct a conclusive new correlation model for Neoproterozoic glacial units of southern Namibia. Therefore, ten different sections and a variety of samples were studied and analysed with respect to field relationships, whole-rock geochemistry, zircon U-Pb dating and Th-U ratios, Hf isotope measurements and zircon grain size analyses, combined with LA-ICP-MS U-Pb dating of cap carbonates.

Our analyses show that (1) sediments deposited during four Neoproterozoic glacial events in southern Namibia all have very similar detrital zircon characteristics, allowing the interpretation of continuous recycling of the same material over the most part of the Neoproterozoic, which is also supported by the whole-rock geochemical analyses, (2) cap carbonates can be analysed for their U-Pb isotope ratios and provide valuable age determinations, if reset and overprinted areas are recognised and avoided for laser ablation, (3) proving the Sturtian and the Marinoan age for the Numees Fm and the Namaskluft Mbr by U-Pb dating their overlying carbonate sequences was finally possible, (4) the Witvlei Grp sedimentation ends at 579 ± 52 Ma, which is the age of the stromatolites of the Okambara Mbr, representing the uppermost deposits of the Witvlei Grp, and this leads to (5) the onset of the Nama Grp sedimentation for southern Namibia is no earlier than 579 ± 52 Ma.

Mud-rich successions can be challenging to interpret accurately, since sedimentary structures such as cross-bedding and ripple marks are often scarce or absent. This makes it difficult to determine the exact environmental and depositional parameters. In order to gain a better understanding of the conditions of such environments, this study aims to compare two of the most important roofing slate deposits in Europe: The Devonian-age “Mosel Slates” and the Ordovician-Silurian-age Truchas Domain.

Until 2019, Rathscheck Schiefer mined the “Mosel Slates” from the Katzenberg mine in the SE Eifel, while companies such as Samaca actively exploit roofing slates near Valdeorras, making Spain one of the largest exporters of roofing slate. These slate mines provide a unique opportunity to gather new insights into the geology of the areas of Mayen (Rhenohercynian Basin) and Valdeorras (Truchas Basin). Both of these areas contain sediments which were deposited in marine shelf settings, although the precise mechanisms of deposition and the precise depositional environment are poorly understood.

This study presents the results of high-resolution facies analyses, both above and below ground, geochemical analyses, including XRD, XRF and CNS measurements, and micro-CT measurements of framboid populations. In both settings, deposition occurred in a low-energy regime on a passive continental margin. Sediments were derived and reworked from the Laurussian and Avalonian continents, respectively. Background sedimentation and density flows were the main mode of deposition. The water column was oxygenated and anoxia was restricted to the sediment in the “Mosel Slates” and to dysoxic episodes in the Spanish slates.

Milankovitch forcing exerts a major control on climate that is recorded in the sedimentary rock record. However, its influence on hyperpycnal flow sedimentation is largely unknown. Hyperpycnites, sediments resulting from hyperpycnal flows, which are related to climate through flood frequency and magnitude, may be valuable tools for understanding aspects of Earth’s paleoclimate. Their origin and distinctive layering have been explained by various mechanisms, including frequency of river breaches, sudden increase in the global hydrological cycle, sea-level fluctuations, and variations in sediment supply. Their potential link to paleoclimate variations commonly remains unexplored in detail. Here we use cyclostratigraphic analysis combined with published high precision U-Pb dating to investigate the influence of Milankovitch forcing on their deposition. A continuous drill core of the ~125-million-year-old Early Cretaceous Laiyang Formation (eastern China) reveals well-defined cyclic hyperpycnal flow patterns. The radioisotopic dating and magnetostratigraphy constrains the formation’s average sedimentation rate, and links the observed cycles to precession, obliquity and mainly orbital eccentricity cycles. Orbital parameters most likely paced the delivery of the hyperpycnal flow sediments mainly by river- and delta-supplied currents from non-marine basin immediately; we conclude that Milankovitch cycles exerted a primary control on hyperpycnal flow sedimentation. Sediment accumulation rates determined from 400 kyr cycle age model show a trend of decreasing and then increasing throughout the Laiyang Formation, which was synchronized with the evolution of sedimentary environment controlled by tectonic activity. This study shows that orbitally-induced climate change can also acted as principle driver on deep-marine terrigenous sediment accumulation within a tectonically active basin.