Abstract. Monsoon-driven fluvial discharge exerts strong environmental control on water quality and carbonate sediment composition in tropical shelf systems, yet the capacity of photosymbiont-bearing calcifiers to sustain carbonate production under monsoon-amplified turbidity and nutrient loading across semi-enclosed platforms remains poorly understood. We here investigate inter-reef facies patterns and benthic foraminiferal assemblages across the Spermonde Archipelago (southwest Sulawesi, Indonesia), a land-attached tropical carbonate shelf subject to seasonal monsoon runoff and intensifying coastal development, using geochemical, sedimentological, and foraminiferal analyses of 51 inter-reef seafloor samples. Nearshore sediments are enriched in mud and organic matter, and dominated by heterozoan and stress-tolerant assemblages, yielding low values for the FoRAM Index (FI; an index that increases with the relative abundance of photosymbiont-bearing foraminifera), indicating conditions unfavourable for photosymbiont-bearing carbonate producers. Statistical separation of nearshore facies from all mid- and outer-shelf assemblages supports a threshold rather than gradual cross-shelf transition. This threshold is spatially asymmetrical, extending further offshore in the northern sector, likely reflecting enhanced retention of fluvially derived material within the more enclosed northern shelf geometry, with the southward Makassar Strait circulation limiting offshore dispersal. Mid- and outer-shelf deposits (~80% of the investigated area) are characterised by foramol facies dominated by benthic foraminifers, bivalves and gastropods, with Amphistegina and Operculina as the dominant symbiont-bearing foraminifera; FI values increase progressively offshore, reflecting improving photic conditions as terrestrially driven seasonal turbidity decreases with distance from the coast. Strong spatial correspondence between foraminiferal assemblages and independently derived sedimentary facies, including convergence of the foraminiferal community transition zone with foramol mud-supported carbonate sediment facies, validates the FI as an ecological proxy beyond shallow reef settings and demonstrates its utility in differentiating carbonate production modes in mesotrophic equatorial systems. These findings support a carbonate production continuum in which photozoan and heterozoan components are organised non-linearly along environmental gradients, with threshold responses emerging from the interaction of platform geometry and catchment-scale terrestrial forcing under seasonal monsoon modulation. We therefore interpret the Spermonde shelf as spatially structured by shifting autotrophic-heterotrophic balances, rather than discrete facies categories.

Toarcian to Aalenian sedimentary deposits in southern Germany have been accumulated in a shallow-marine, epicontinental shelf environment. The according successions are dominated by marlstones, thick claystones and argillaceous siltstones, with increasing percentages of sandstones towards the top of the Aalenian. While the Toarcian, including the TOC-rich paper shales of the Toarcian Oceanic Anoxic Event (T-OAE), is characterized by distinct lithologies, resulting in a number of hiatuses, Aalenian sedi­ments are likely to represent a relatively complete stratigraphic record. Although the investigated sequences are located in a region that has been known for its famous Jurassic sequences for more than 150 years, the sedimentary evolution and paleoclimatic significance of these successions, remain largely unexplored on a basin-wide scale. Here we present a suite of high-resolution x-ray fluorescence (XRF) core scanning, stable organic carbon isotope and biostratigraphy data to identify Transgressive-Regressive cycles during the Late Toarcian to Aalenian. Results are based on four scientific drill cores of 200 - 250 m length, taken on a profile over a distance of about 300 km. Resulting trends in elemental Si/Al ratios, which are indicative for subtle grain-size variations, combined with sedimentological observations on ichnofacies and bedform development were used to reconstruct shoreline trajectories and establish a sequence stratigraphic framework. Our study mainly focus the thick and largely homogenous lower Aalenian Opalinuston Formation.

Low-lying coral reef islands are presumed to be highly vulnerable landforms to the effects of climate change. Rising sea levels, changes in wave regimes and reef degradation are all considered key threats to their future persistence and habitability. While a number of studies have examined morphological changes on islands over multidecadal timescales, there is a paucity of high-frequency data from recent years that discern variability in shoreline change trends at the local scale. In this study, we used frequently sampled high-resolution satellite imagery covering the past two decades and analysed the morphological evolution and dynamics of 22 reef islands of the Spermonde Archipelago at the southwest coast of Sulawesi, Indonesia - a location deemed as a climate change hotspot with sea-level rise rates higher than the global average, and anthropogenically affected reef ecosystems. Analysis of 4,329 transects cast across 192 recorded shorelines revealed a balance in erosional and accretionary response. Specifically, 32% of transects were characterized by statistically significant accretion, 29% by erosion and the remaining exhibited no significant change. The magnitude of shoreline changes showed high spatial variability across the archipelago, with marked differences between islands perched on patch reefs on the outer shelf and those in the mid-shelf and nearshore. Archipelago-wide, irrespective of a net gain or loss in land area on islands, accretion was predominant on the western margins, while the eastern margins experienced relatively high degrees of erosion, leading to a westward migration of 55% of the islands on their reef platforms. Collectively, this study provides the first high-resolution shoreline change record for the archipelago, explores contemporary patterns of island morphological change and highlights the importance of high-frequency sampling in reef island studies for understanding projections of island change and efforts towards developing robust adaptation strategies and decision-making.

Reef islands, elevated only a few meters above sea-level and restricted in area, are not only confronted with rising sea-levels, but the surrounding reef ecosystems, which are the only source of sediment maintaining those islands, are threatened by global (e.g. ocean warming and acidification) and local anthropogenic (e.g. pollution and destructive fishing methods) stressors affecting many tropical coastal areas. These stressors can increase coral mortality and lead to shifts from coral- to macroalgal-domination, likewise altering the production of skeletal carbonate sediment and ultimately endanger the physical persistence of reef islands. Here we study the evolution of an Indonesian reef island that has been inhabited since the 20th century. By analyzing the sedimentary record covering the last 5800 years from sediment cores taken on the island, we study the formation processes during the Holocene. For understanding the spatial dynamics, we compare the sediment record of the past decades with observations from satellite imagery data. Two shifts in the sedimentological composition over time point to alterations in the sediment-supplying reef ecosystems. The first sedimentological shift occurred from 3900 years BP on, shortly before the initial formation of the island, when the skeletal composition was diversified, presumably reflecting the modification of the reef ecosystem following a sea-level drop. A second sedimentological shift in the youngest sediments is marked by increased proportions of the calcifying green algae Halimeda , indicating that the reef ecosystem has shifted toward algal-domination, presumably reflecting increasing anthropogenic pressure. Of significance, shoreline change analysis reveals that the island is in an accreting state and has grown by 13 % in surface area over the past 24 years. Our findings suggest that the compositional alterations in sediment supply did not destabilize the reef island, and underline the adaptive potential of these landforms. (c) 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

In three dimensions, dipole-dipole interactions which alter atomic level shifts and spontaneous decay rates only persist over distances comparable to the wavelength of the emitted light. In this paper we show that it is possible to significantly extend the range of these interactions with the help of a partially transparent asymmetric mirror interface. Suppose two two-level atoms are placed on opposite sides of the interface, each at the position of the mirror image of the other. In this case, their emitted light interferes almost exactly as it would when the atoms are right next to each other. Hence their dipole-dipole interaction assumes an additional maximum, even when the actual distance of the atoms is several orders of magnitude larger than the transition wavelength. Although the resulting ultralong-range interactions are in general relatively weak, we expect them to find applications in quantum technology, like non-invasive quantum sensing.

From 2019 to 2021, three cores were drilled at different locations in the southern German Swabian Alb as part of the SEPIA project (Sequence Stratigraphy of the Aalenian in Southern Germany). They comprise sediments of 200 to 250 m length and are penetrating Lower and Middle Jurassic strata from the Pliensbachian to Bathonian stages (~ 190-166 Ma). The aim of this project is the development of a sequence stratigraphic model of the South German Basin at the transition from the Lower to Middle Jurassic time. Conclusions should be drawn towards the source area of the sediments as well as on the influence of sea level fluctuations on sedimentation.Today, the Swabian Alb is a SW-NE trending mountain chain consisting of mainly carbonate rocks, and is one of the most distinctive regions in Germany where Jurassic strata is cropping out. During the middle Jurassic, Europe was almost completely covered by a shallow epi-continental sea including several small emerging areas or islands, located at latitudes about 15° lower than today. Southern Germany experienced predominant deposition of fine clastic sediments in a tropical climate. The most common sediments of this period are dark clays and oolithic ironstones, whereas condensation and discontinuity surfaces occur in many instances. Accommodation space for these sediments was not only generated by changes in sea level, but also by continuing subsidence of the area, explaining the inhomogeneous thickness and changes in facies of the sediments.The geophysical downhole logging data of the stratigraphic record is used to develop a lithological classification and correlation of the boreholes sediments by the application of a cluster analysis to the data. Furthermore, the downhole logging data is used to perform cyclostratigraphy in selected intervals. The focus of the intervals chosen for cyclostratigraphy lies on the Aalenian stage, as this stage holds the most continuous and extended record in all three boreholes. Predicted timespans of these intervals yield similar results of ~800-1100 ka for all three boreholes and might provide a new benchmark for progressive improvement, especially for cyclostratigraphic analyses of the Lower Aalenian Opalinusclay Formation.

Many lagoons surrounded by reefs are partially or completely infilled with reef-derived detrital carbonate sediment. Sediment deposits in such restricted environments are archives of prevailing environmental conditions during lagoon infill. For Indonesia, no paleoenvironmental reconstructions based on Holocene lagoon sediments exist. Here we analyze the sedimentary record obtained from five percussion cores penetrating 10 m into the unconsolidated subsurface of a reef island in the Spermonde Archipelago, Indonesia. The combined compositional, textural and chronostratigraphic analyses reveal that the sedimentary infill of the lagoon underlying the island, starting 6900 years cal BP, was interrupted between 5800 and 4400 years cal BP, when sea level was ~ 0.5 m higher than at present, and monsoon intensity was lower. After the intensity of the monsoons increased to modern levels, and sea level dropped to its present position, lagoonal sedimentation was re-initiated and created the foundation for an island that built up since 3000 years cal BP. Our study provides the first geological evidence for the strong sensitivity of detrital carbonate systems in Indonesia to fluctuations in sea level and dominant wind direction. It thus sheds light on how changing environmental conditions in the context of global warming could affect the morphological development of reef systems, and thereby also habitable coastal areas.

<p>Aalenian sedimentary deposits in southern Germany have accumulated in a shallow-marine, epicontinental shelf environment. These accumulations are dominated by thick claystones and argillaceous siltstones, with increasing percentages of sandstones towards the top. Aalenian sediments are likely to represent a relatively complete stratigraphic record, however, the sedimentary evolution and paleoclimatic significance of these typically poorly exposed deposits remain largely unexplored. Here we present a suite of high-resolution x-ray fluorescence (XRF) core scanning data from southern Germany to identify Transgressive-Regressive cycles during the Aalenian stage. Results are based on three scientific drill cores of 200 – 250 m length that have been analyzed with an Avaatech XRF Core Scanner at a 10 mm sampling interval (10 keV, 500 µA). Resulting trends in elemental Si/Al ratios, which are indicative for subtle grain-size variations, combined with sedimentological observations on ichnofacies and bedform development were used to reconstruct shoreline trajectories and establish a sequence stratigraphic framework for the thick and largely homogenous lower Aalenian Opalinuston Formation.</p>

The Laurentide ice sheet was the largest late Pleistocene ice mass and the largest contributor to Holocene pre-industrial sea-level rise. While glaciological dates suggest final ice sheet melting between 8 and 6 ka, inversion of sea-level data indicates deglaciation at ca. 7 ka. Here, we present new chronostratigraphic constraints on Laurentide ice sheet disappearance based on Holocene relative sea-level observations from the tectonically stable north coast of Java, Indonesia. Age-elevation data from the flat upper surfaces of 13 fossil intertidal corals (i.e., microatolls) indicate that the Java Sea experienced a relative sea level of 1.3 ± 0.7 m above present between 6.9 and 5.3 ka. To determine uncaptured relative sea-level trends within the observational uncertainties of this apparently constant highstand, we analyzed the internal structure of three sliced microatolls from the same site to produce a high-resolution data set. These data were used to statistically model relative sea-level rates and trends. Employing the data with the model provided evidence for a short-lived rise of relative sea level from 1.0 ± 0.3 m above present at 6.7 ± 0.1 ka to 1.9 ± 0.3 m above present at 6.4 ± 0.1 ka. The end of this rise likely represents the last input of meltwater from the vast Laurentide ice sheet, which, consequently, collapsed at least 400 yr later than assumed by some widely used models of glacial isostatic adjustment. Incorporating these new results into such predictive models will help to better understand the geographical variability of future sea-level rise as a result of global warming.

Supplemental text and tables.

Abstract. In a recent report, the German Federal Company for Radioactive Waste Disposal (BGE) estimated the probable duration of exploration activities within potential siting regions (BGE, 2022). Based on many years of expertise regarding the exploration of the subsurface, we outline in this contribution that the BGE (2022) likely underestimates the time necessary to characterize claystones within potential siting regions. Our latest experience originates from two research projects that developed sequence stratigraphic frameworks for the largely homogenous claystone successions of the Lower Cretaceous in northern Germany (Thöle et al., 2020) and the Middle Jurassic in southern Germany, respectively. Although the specific study areas are not considered in the site selection procedure, both stratigraphic units are reviewed to potentially host a nuclear waste repository. Accordingly, our hands-on experience might constitute a highly relevant contribution to the ongoing debate. Within each study area, drill cores were extracted from four boreholes with a total length of ∼660 m (northern Germany) and ∼930 m (southern Germany). After the drilling campaigns, each having taken approx. 5–6 weeks, the cores were split, photographed in high resolution, lithologically described, scanned with an X-Ray fluorescence (XRF) core scanner (10 mm scan interval) to determine the elemental distribution, and sampled for lithological, mineralogical and geochemical analyses at a resolution of 1 m, which took approx. 12 months. However, the most time-consuming steps were the analysis and interpretation of the stratigraphy and particularly the mineralogical investigations. With a sampling resolution of 1 m, an analysis time of approx. 6 months per 250 core meters is a robust reference. We reckoned a total duration of 5 years for the workload in each of the abovementioned research projects. Obviously, the duration of claystone exploration will vary, depending on the number and length of the core drillings per siting region, in addition to the sampling resolution. However, if BGE aims to characterize claystones with a degree of detail comparable to our projects, the estimated 42 months (see Table 3 in BGE, 2022) will likely be insufficient.

In three dimensions, dipole-dipole interactions which alter atomic level shifts and spontaneous decay rates only persist over distances comparable to the wavelength of the emitted light. To provide novel tools for quantum technology applications, like quantum sensing, many attempts have been made to extend the range of these interactions. In this paper we show that such an extension can be achieved with the help of partially transparent asymmetric mirror interfaces without involving negative refractive index metamaterials. Suppose two atoms are placed on opposite sides of the interface, each at the position of the mirror image of the other. In this case, their emitted light interferes exactly as it would when the atoms are right next to each other. Hence their dipole-dipole interaction assumes an additional maximum, even when the actual distance of the atoms is several orders of magnitude larger than their transition wavelength.

<p>Reef islands accumulate as shallow landforms on or adjacent to reef complexes and are mainly composed of reef-derived carbonate sediment. Due to their unconsolidated and low-lying nature, reef islands are exposed to hydrodynamic processes, whereby they naturally experience erosion and accumulation. In order to compensate deficits of sediments lost during erosion, a sufficient supply of suitable carbonate sediment is required for accumulation. Under changing environmental conditions, the reefs are exposed to multiple stress factors that, among other things, can alter carbonate production and thus also threaten the stability of the reef islands. Hence, it is of importance to understand how past changes in the production of carbonate sediment have affected the evolution of reef islands systems, in order to assess potential future scenarios. Here we reconstruct the Holocene and recent sedimentological dynamics from one inhabited Indonesian reef island on the outer shelf of the Spermonde Archipelago, directly bordering the Strait of Makassar. We investigate the carbonate facies from sediment obtained from deep push cores up to 8 meters below surface and from shallow, hand-drilled boreholes. Targeted radiocarbon dating helps to reveal the temporal understanding of facies evolution and formation dynamics. Our data show that the island complex started to form in the mid-Holocene, around 6,400 years cal BP. The carbonate sediment from this time is almost exclusively composed of sand-sized coral fragments. Over time, the sediment composition becomes more diverse, with increased abundances of mollusks and algae, likely reflecting the ecological evolution of the reef. The shallow samples close to mean relative sea-level show radiocarbon ages of 4,000 to 3,000 years cal BP, suggesting that the initial island formed around this time and accreted in the following millennia. Of note, the proportions of the green algae Halimeda is even further increased in the youngest sediments. Overall, this suggests that the island has been able to continue growing despite changes in the ecosystems that provide the sediment, and that the increased production of green algae may have even promoted island accretion in general. Our study provides valuable insights into the dynamics of reef island development in the context of evolving reef systems and extends the understanding of Holocene island formation in the study area.</p>

Early-diagenetic cementation of tropical carbonates results from the combination of numerous physico-chemical and biological processes. In the marine phreatic environment it represents an essential mechanism for the development and stabilization of carbonate platforms. However, diagenetic cements that developed early in the marine phreatic environment are likely to become obliterated during later stages of meteoric or burial diagenesis. When lithified sediment samples are studied, this complicates the recognition of processes involved in early cementation, and their geological implications. In this contribution, a petrographic microfacies analysis of Holocene Halimeda segments collected on a coral island in the Spermonde Archipelago, Indonesia, is presented. Through electron microscopical analyses of polished samples, this study shows that segments are characterized by intragranular cementation of fibrous aragonite, equant High-Mg calcite (3.9 to 7.2 Mol% Mg), bladed Low-Mg calcite (0.4 to 1.0 Mol% Mg) and mini-micritic Low-Mg calcite (3.2 to 3.3 Mol% Mg). The co-existence and consecutive development of fibrous aragonite and equant High-Mg calcite results initially from the flow of oversaturated seawater along the aragonite template of the Halimeda skeleton, followed by an adjustment of cement mineralogy towards High-Mg calcite as a result of reduced permeability and fluid flow rates in the pores. Growth of bladed Low-Mg calcite cements on top of etched substrates of equant High-Mg calcite is explained by shifts in pore water pH and alkalinity through microbial sulphate reduction. Microbial activity appears to be the main trigger for the precipitation of mini-micritic Low-Mg calcite as well, based on the presumable detection of an extracellular polymeric matrix during an early stage of mini-micrite Low-Mg calcite cement precipitation. Radiocarbon analyses of five Halimeda segments furthermore indicate that virtually complete intragranular cementation in the marine phreatic environment with thermodynamically/kinetically controlled aragonite and High-Mg calcite takes place in about 100 years. Collectively, this study shows that early-diagenetic cements are highly diverse and provides new quantitative constraints on the rate of diagenetic cementation in tropical carbonate factories.

Large benthic foraminifera are major carbonate components in tropical carbonate platforms, important carbonate producers, stratigraphic tools and powerful bioindicators (proxies) of environmental change. The application of large benthic foraminifera in tropical coral reef environments has gained considerable momentum in recent years. These modern ecological assessments are often carried out by micropalaeontologists or ecologists with expertise in the identification of foraminifera. However, large benthic foraminifera have been under‐represented in favour of macro reef‐builders, for example, corals and calcareous algae. Large benthic foraminifera contribute about 5% to modern reef‐scale carbonate sediment production. Their substantial size and abundance are reflected by their symbiotic association with the living algae inside their tests. When the foraminiferal holobiont (the combination between the large benthic foraminifera host and the microalgal photosymbiont) dies, the remaining calcareous test renourishes sediment supply, which maintains and stabilizes shorelines and low‐lying islands. Geological records reveal episodes (i.e. late Palaeocene and early Eocene epochs) of prolific carbonate production in warmer oceans than today, and in the absence of corals. This begs for deeper consideration of how large benthic foraminifera will respond under future climatic scenarios of higher atmospheric carbon dioxide ( p CO 2 ) and to warmer oceans. In addition, studies highlighting the complex evolutionary associations between large benthic foraminifera hosts and their algal photosymbionts, as well as to associated habitats, suggest the potential for increased tolerance to a wide range of conditions. However, the full range of environments where large benthic foraminifera currently dwell is not well‐understood in terms of present and future carbonate production, and impact of stressors. The evidence for acclimatization, at least by a few species of well‐studied large benthic foraminifera, under intensifying climate change and within degrading reef ecosystems, is a prelude to future host–symbiont resilience under different climatic regimes and habitats than today. This review also highlights knowledge gaps in current understanding of large benthic foraminifera as prolific calcium carbonate producers across shallow carbonate shelf and slope environments under changing ocean conditions.

Ecosystem Design (ED) is an approach for constructing habitats that places human needs for ecosystem services at the center of intervention, with the overarching goal of establishing self-sustaining habitats which require limited management. This concept was originally developed for use in mangrove ecosystems, and is understandably controversial, as it markedly diverges from other protection approaches that assign human use a minor priority or exclude it. However, the advantage of ED lies within the considered implementation of these designed ecosystems, thus preserving human benefits from potential later disturbances. Here, we outline the concept of ED in tropical carbonate depositional systems and discuss potential applications to aid ecosystem services such as beach nourishment and protection of coastlines and reef islands at risk from environmental and climate change, CO2 sequestration, food production, and tourism. Biological carbonate sediment production is a crucial source of stability of reef islands and reef-rimmed coastlines. Careful implementation of designed carbonate depositional ecosystems could help counterbalance sea-level rise and manage documented erosion effects of coastal constructions. Importantly, adhering to the core ethos of ED, careful dynamic assessments which provide a balanced approach to maximizing ecosystem services (e.g., carbonate production), should identify and avoid any potential damages to existing functioning ecosystems.

Reef islands in monsoonal regions undergo constant erosion and accumulation, making seasonally shifting morphologies part of their nature. Additionally, sea-level rise alongside climate change is thought to be incisive and challenge coastal communities. With multiple pressures acting on sediment-generating coral reef ecosystems, changes in sediment supply may force further response of these dynamic landforms. Here we present new sedimentological data from a larger reef island in the Spermonde Archipelago, Indonesia. By evaluating the subsurface data in the context of the island’s morphological behavior, we reconstruct its agile past and present. Based on remote sensing data complemented by reports of local citizens, we find the inhabited island to have tripled its surface area in the past century, however also losing more than 10% of surface area in the recent decades. The deeper sediments of the island are dominated by coral fragments, the youngest and uppermost sediments indicate the green algae Halimeda as dominating material contributor. Our study thereby (1) underlines the highly and far-reaching dynamics of reef islands and (2) suggests their adaptive potential to altering material budgets.

Lower and Middle Jurassic sedimentary deposits in southern Germany have accumulated in a shallow-marine shelf environment and are typically dominated by clayey lithologies with minor occurrences of sandstones and limestones. The sedimentary evolution and paleoclimatic significance of these poorly exposed deposits often remain largely unexplored. Here we present a suite of high-resolution x-ray fluorescence (XRF) core scanning data from southern Germany covering the Upper Toarcian and Aalenian stages. The overall objective of this study is to identify Transgressive-Regressive cycles based on the analysis of three cores obtained during scientific drilling campaigns in 2019-2021. Cores have been analyzed with an Avaatech XRF Core Scanner at a 10 mm sampling interval, an energy of 10 keV and a current of 500 µA to measure element intensities ranging from aluminium through iron. Resulting trends in elemental ratios indicative for subtle grain-size variations such as Si/Al are used to reconstruct shoreline trajectories and establish a sequence stratigraphic framework (see Thöle et al. 2020). Particularly the thick and largely homogenous Opalinuston Formation appears suitable in that respect, likely resulting from extraordinarily high sedimentation rates during the lower Aalenian in southern Germany, thus providing a complete but unexplored archive of paleoclimatic signals. References:Thöle, H., Bornemann, A., Heimhofer, U., Luppold, F. W., Blumenberg, M., Dohrmann, R., & Erbacher, J. (2020). Using high‐resolution XRF analyses as a sequence stratigraphic tool in a mudstone‐dominated succession (Early Cretaceous, Lower Saxony Basin, Northern Germany). The Depositional Record, 6(1), 236-258.

The local observables of the quantised electromagnetic field near a mirror-coated interface depend strongly on the properties of the media on both sides. In macroscopic quantum electrodynamics, this fact is taken into account with the help of optical Green’s functions which correlate the position of an observer with all other spatial positions and photon frequencies. Here we present an alternative, more intuitive approach and obtain the local field observables with the help of a quantum mirror image detector method. In order to correctly normalise electric field operators, we demand that spontaneous atomic decay rates simplify to their respective free space values far away from the reflecting surface. Our approach is interesting, since mirror-coated interfaces constitute a common basic building block for quantum photonic devices.