The Tonasa Formation is one of the most widely distributed rock units in the southern arm of Sulawesi, reaching thicknesses of 1,750 to 3,000 meters. It consists of interbedded limestone and Globigerina marl deposited on a carbonate platform that flourished as the Indo-Australian, Pacific, and Eurasian plates collided, eventually sculpting Sulawesi into its distinctive K-shaped outline. Yet despite its grandeur and its role in creating spectacular karst landscapes, the formation’s stratigraphic record remains incomplete in places. In the Jeneponto area, Oligocene to Early Miocene strata were long considered poorly exposed and poorly known, leaving a gap in scientists’ understanding of how this tropical carbonate platform responded to global climate change roughly 34 million years ago.

To fill that gap, the research team turned to the Karama area, where the formation is beautifully exposed along the coast as alternating beds of limestone and marl. They sampled 23 layers using measured stratigraphy, preparing each sample as a smear slide sealed under a 24 by 24 millimeter cover glass. Under a polarizing microscope at 1,000 times magnification, the fossil content of the rocks came into view: a constellation of coccoliths and related structures produced by nannoplankton, the primary producers of ancient seas. Because these organisms evolved rapidly and were hugely abundant, their first and last appearances in the rock record provide datums, time markers that allow geologists to correlate strata across entire ocean basins with remarkable precision.

The analysis identified 20 species in the Karama A section, including members of the genera Coccolithus, Cyclicargolithus, Reticulofenestra, Dictyococcites, Discoaster, Sphenolithus, and Zygrhablithus, along with the distinctive Braarudosphaera bigelowii. From the vertical distribution of these species, the researchers recognized three key biostratigraphic datums. The first is the First Occurrence of Sphenolithus pseudoradians, which marks the boundary between zones NP19 and NP20 in the standard zonation of Martini from 1971. The second is the First Occurrence of Sphenolithus distentus, corresponding to the CP16/CP17 boundary of Okada and Bukry’s 1980 scheme, equivalent to NP22/NP23, found in layer 12 of the section. The third is the Last Occurrence of Sphenolithus predistentus in layer 18, defining the NP23/NP24 boundary.

Together, these datums establish that the studied part of the Tonasa Formation at Karama A spans the Late Eocene to the Middle Oligocene. That conclusion matters because it means the Eocene/Oligocene boundary itself, the dividing line between the epochs, is captured within this section. This was precisely the interval when Earth’s climate flipped from the Cenozoic’s greenhouse state toward icehouse conditions, as massive ice sheets grew on Antarctica and global temperatures plummeted. Previous work on the Karama area using planktonic foraminifera had identified only a latest Eocene age, so the new nannofossil data extend the known record substantially and help place this section in the middle part of the formation’s regional stratigraphic framework.

The story the fossils tell is not only about time but also about temperature. Calcareous nannoplankton distribution is strongly tied to surface water temperature and nutrient availability, making their assemblages natural thermometers for ancient oceans. Certain genera carry well-established climatic affinities: Discoaster, a lower photic zone dweller, is considered an indicator of warm, oligotrophic waters, as are Sphenolithus and Zygrhablithus bijugatus. Coccolithus pelagicus, by contrast, is a classic cold-water species that becomes rare or absent in low latitudes. The relative abundance of these taxa through the section therefore allows researchers to track how conditions in the basin changed as global climate deteriorated.

In the Karama A section, warm-water indicators such as Discoaster, Sphenolithus, and Zygrhablithus bijugatus are present from the bottom to the top, which the team interprets as evidence that the basin remained in warm-water conditions overall. But the details are revealing. Species diversity and specimen counts tended to decline from the Eocene into the Oligocene, mirroring the long-term global cooling documented in marine and terrestrial records worldwide. Discoaster tanii decreased steadily and disappeared by layer 18, while the numbers of Discoaster and Sphenolithus individuals dropped through the interval. Poor preservation, including diagenetic overgrowth, complicated species identification in places, but the overall pattern of decline is clear.

Intriguingly, the trend did not end in a simple collapse. In the upper part of the Middle Oligocene, the warm-water taxa rebounded, with Discoaster, Sphenolithus, and Zygrhablithus becoming more abundant again, while Cyclicargolithus floridanus and Reticulofenestra bisectus remained abundant and even increased toward the top of the section. The researchers interpret this recovery as evidence that although the carbonate environment stayed fundamentally warm, water temperatures dipped during the Oligocene cooling and then partially recovered. The assemblage changes are gradual rather than a sharp turnover, suggesting the tropical platform experienced the global transition as a gentle but persistent decline in temperature, reducing both diversity and abundance of the most heat-loving species.

The findings also resolve a lingering puzzle in Sulawesi geology. Earlier research had reported that Oligocene strata of the Tonasa Formation in the Jeneponto area were unknown, yet the carbonate succession there was thought to range from the Late Eocene to the Middle Miocene. By demonstrating a Late Eocene to Middle Oligocene age for the Karama A section, the study shows that Oligocene rocks are indeed present and datable in Jeneponto, and it complements previous nannofossil work in the Barru area that yielded a Middle Eocene to Early Miocene age. The result strengthens stratigraphic correlations between the Pangkajene and Jeneponto regions and refines the picture of how the Tonasa Carbonate Platform, whose accommodation space was controlled largely by subsidence, evolved through a time of global climatic upheaval.

More broadly, the study underscores why nannofossils remain among the most powerful tools in carbonate sediment research. These primary producers responded sensitively to the surface water conditions of their time, and their rapid evolutionary turnover allows biostratigraphers to slice the Eocene and Oligocene into fine zones using the standard Martini and Okada and Bukry frameworks. For Indonesia, a nation whose geology was forged by the collision of three major plates, each such study adds a piece to the intricate puzzle of island arc evolution and tropical paleoceanography. For climate scientists, the Karama A section offers another ground-truth record of how marine ecosystems in low-latitude carbonate settings registered the last great transition from greenhouse to icehouse Earth, a transition whose lessons resonate strongly in an era of rapid warming.

Subject of Research: Biostratigraphy and paleoclimate of the Eocene to Oligocene Tonasa Formation in South Sulawesi, Indonesia, based on calcareous nannofossils

Article Title: The Eocene to Oligocene boundary and paleoclimatic indications based on calcareous nannofossils of Tonasa Formation, South Sulawesi, Indonesia

Article References: Farida, M., Jaya, A., Ahmad, A., & Nugraha, J. (2024). The Eocene to Oligocene boundary and paleoclimatic indications based on calcareous nannofossils of Tonasa Formation, South Sulawesi, Indonesia. Fossil Record, 27(1), 221-231. https://doi.org/10.3897/fr.27.96985

Image Credits: AI Generated

DOI: 10.3897/fr.27.96985

Keywords: calcareous nannofossils, Eocene Oligocene boundary, Tonasa Formation, South Sulawesi, biostratigraphy, paleoclimate, Sphenolithus, Discoaster, carbonate platform, Oligocene cooling, Indonesia, stratigraphy

The investigated section is remarkably thin: just 16 metres of rock, described from the upper part of the Amaltheenton Formation through the famous Posidonienschiefer and the Jurensismergel Formation to the base of the Opalinuston Formation. Despite this modest thickness, the succession covers a vast stretch of time. Ammonite biostratigraphy, based on roughly 425 determinable ammonites recovered in situ, indicates more than 9 metres of Upper Pliensbachian, only 1.15 to 1.20 metres for the entire Lower Toarcian, 5.04 metres for the Upper Toarcian, and more than 0.5 metres for the Lower Aalenian. All Toarcian ammonite zones and almost all subzones are present, even though major parts of the Tenuicostatum Zone and the Fallaciosum Subzone are missing. Such completeness in so little sediment is a hallmark of condensation, where slow sedimentation and erosion compress millions of years into centimetres of rock.

Geochemical analyses of the bulk rock revealed a striking pattern. Carbonate contents are low in the Amaltheenton, then jump suddenly to as much as 94 weight percent at the base of the Posidonienschiefer and remain consistently high in its lower part, before successively declining through the Jurensismergel into the basal Opalinuston. Organic carbon contents of the Posidonienschiefer at Dörlbach appear comparatively low, averaging 2.45 weight percent, far below the 6.77 weight percent measured at the classic Swabian Alb section of Dotternhausen. But when the authors normalized organic carbon to the carbonate-free silicate fraction, the values became almost identical: 11.18 weight percent at Ludwigskanal versus 12.22 weight percent at Dotternhausen. The apparent difference is therefore a dilution effect, caused by the unusually high carbonate contents at the Franconian section, not a genuine difference in organic matter production or preservation.

Normalized to the silicate fraction, the organic carbon record shows a clear first maximum in the Exaratum Subzone, with values reaching up to 17.6 weight percent in the basal Laibstein beds, and a second maximum in the interval from the Falciferum Shale to the Monotis Bed, up to 14.1 weight percent. This pattern matches the peak of the Toarcian Oceanic Anoxic Event, a global episode of widespread seafloor oxygen depletion around 183 million years ago that has been linked to massive volcanic carbon release, seawater warming, and biotic turnover. Intriguingly, the Ludwigskanal record differs from most central European sections in one respect: high organic carbon levels persist into the middle parts of the Upper Toarcian, suggesting that anoxic or oxygen-poor bottom waters lingered longer in this current-swept part of the NW European Epicontinental Seaway.

The ammonite assemblages recovered bed by bed allowed a high-resolution biostratigraphic subdivision. The Posidonienschiefer begins with an erosive discontinuity marked by reworked concretions of the underlying Amaltheenton, and the laminated limestone concretions of the Laibstein I bed yielded Tiltoniceras antiquum just a few centimetres above the base, representing the latest Semicelatum Subzone. The overlying Laibstein II bed contains an assemblage typical of the Elegans Subzone, including Harpoceras serpentinum and abundant holoplanktonic gastropods of the species Coelodiscus minutus. A single compressed specimen of Harpoceras falciferum, the index fossil of the Falciferum Zone, was recovered from the Falciferum Shale and is figured for the first time for the Franconian Alb. Higher beds with densely packed Meleagrinella shells, the Dactylioceras Bed and the Monotis Bed, belong to the Commune Subzone, while the Bifrons Shale contains Hildoceras semipolitum, defining the Semipolitum Horizon at the top of the Bifrons Zone, a horizon detected for the first time in the region.

The Upper Toarcian succession proved equally informative. The Variabilis Shale is characterized by abundant pyrite-preserved Catacoeloceras raquinianum, Pseudolioceras compactile, and Lytoceras sublineatum, with compressed Haugia variabilis concentrating in its topmost centimetres. A change in the ammonoid assemblage in the thin marl bed below the famous Belemnite Battlefield, with Pseudogrammoceras subregale and Haugia cf. phillipsi, marks the Illustris Subzone, another first for the area. The Belemnite Battlefield itself, a grey bituminous calcareous marl crowded with belemnite rostra and bored phosphorite nodules, is poor in ammonoids but consistent with the upper Variabilis Zone. The overlying Main Phosphorite Bed represents a condensation horizon spanning the transition from the Variabilis to the Thouarsense Zone, and the bituminous Toarcensis Shale above it contains a monospecific assemblage of Grammoceras thouarsense. No evidence of the Fallaciosum Subzone was found at Dörlbach, although it is known from the neighbouring section of Hausheim.

The uppermost Toarcian and the transition to the Aalenian complete the picture. A clear erosive discontinuity at the base of the Dispansum Zone, marked by a belemnite accumulation with corroded phosphorites, is followed by marls with Phlyseogrammoceras dispansum, Alocolytoceras rugiferum, and Hammatoceras insigne. First Dumortieria appear near the top of this bed, with Dumortieria insignisimilis marking the base of the Levesquei Subzone, the Dumortieri Horizon, again detected for the first time in the region. An ammonite accumulation in the topmost centimetres with Dumortieria pseudoradiosa, D. radiosa, and D. striatulocostata marks the onset of the Pseudoradiosa Subzone. A condensed bed with Cotteswoldia mactra defines the base of the Mactra Subzone of the Aalensis Zone, and the overlying marls with Cotteswoldia aalensis, Pleydellia subcompta, and Pleurolytoceras hircinum represent the Aalensis Subzone. The youngest ammonite subzone of the Lower Jurassic, the Torulosum Subzone, is documented by a condensed horizon with Pleydellia buckmani, P. lotharingica, and Pleurolytoceras torulosum. The Toarcian-Aalenian boundary is drawn in analogy to a neighbouring drill section that yielded Leioceras opalinum immediately above the equivalent of this bed.

On the basis of these discontinuities, condensed beds, and correlations with neighbouring sections across southern Germany, the authors propose a sequence stratigraphic interpretation built on transgressive-regressive cycles of third order. The Posidonienschiefer Formation corresponds to a single third-order transgressive-regressive sequence, from the top of the Hawskerense Subzone to a fucoid bed at the top of the Variabilis Subzone, with a maximum flooding surface at the top of the Falciferum Zone. The Jurensismergel Formation exhibits two such sequences: the first ranges from the base of the Illustris Subzone, marked by the Intra-Variabilis-Discontinuity, to the top of the Thouarsense Zone, with a maximum flooding surface within the Thouarsense Zone; the second extends from the erosive base of the Dispansum Zone to the top of the Aalensis Subzone, with a maximum flooding surface at the Pseudoradiosa-Aalensis Zone boundary. The Opalinuston begins with a new sequence at the base of the Torulosum Subzone.

One of the most consequential reinterpretations concerns the Belemnite Battlefield. Earlier workers had considered this belemnite accumulation a maximum regression surface at the base of the Jurensismergel, with its components reworked from the Posidonienschiefer below. The new study argues otherwise: the bored phosphorite nodules are not derived from the bituminous shales below, and correlations with Swabian Alb sections indicate an erosive discontinuity at the base of the marl bed beneath the battlefield. The Belemnite Battlefield therefore reflects a transgressive ravinement surface within the first Jurensismergel sequence, formed by winnowing along a coast-parallel seawater current, consistent with the formation model proposed by Urlichs in 1971. This reinterpretation also shifts the lithostratigraphic boundary between the Posidonienschiefer and Jurensismergel formations, placing the Fucoid Bed at the top of the Posidonienschiefer and the poorly bituminous marls below the battlefield at the base of a new stratigraphic sequence.

The study also reveals a consistent pattern in fossil preservation that tracks sea-level change. Transgressive system tracts of the third-order cycles are commonly phosphoritic, while some regressive system tracts show pyrite preservation of ammonites. The maximum regression surfaces at the base of the Toarcian and within the Variabilis Zone reflect significant submarine erosion and relief formation by seawater currents, an effect less pronounced at the base of the Dispansum Zone and at the Jurensismergel-Opalinuston boundary. In the Swabian Alb, submarine swells remaining after Variabilis Zone erosion show aphotic microbialites in the Toarcensis Zone, indicating highly reduced sedimentation during maximum flooding. The litho-, bio-, and sequence stratigraphic framework established at the Ludwigskanal now serves as a scaffold for future isotope and biogeochemical studies on the Toarcian Oceanic Anoxic Event and its recovery phase, in this seawater current-affected part of the epicontinental seaway, where seawater temperatures, current systems, and the persistence of oxygen depletion can be disentangled with unprecedented stratigraphic precision.

Subject of Research: Toarcian biostratigraphy and sequence stratigraphy of the Ludwigskanal section, Franconian Alb, southern Germany

Article Title: Biostratigraphy and sequence stratigraphy of the Toarcian Ludwigskanal section (Franconian Alb, Southern Germany)

Article References: Arp, G., Gropengießer, S., Schulbert, C., Jung, D., & Reimer, A. (2021). Biostratigraphy and sequence stratigraphy of the Toarcian Ludwigskanal section (Franconian Alb, Southern Germany). Zitteliana, 95, 57-94. https://doi.org/10.3897/zitteliana.95.56222

Image Credits: AI Generated

DOI: 10.3897/zitteliana.95.56222

Keywords: Biostratigraphy, sequence, stratigraphy, Toarcian, Ludwigskanal, section, Franconian, Southern, Germany, scientific research

The research grew out of fieldwork on the overlying Wedelsandstein Formation, when the team extended its survey downward into the Achdorf Formation and the uppermost Opalinuston Formation. What they found was unexpected: beds that earlier workers, notably Hahn in 1975, had described as nearly barren of ammonites turned out to yield a diverse assemblage of these iconic spiral-shelled cephalopods. The microfaunal samples proved equally rewarding, packed with ostracods, the tiny bivalved crustaceans whose shells, often less than half a millimetre long, preserve an exquisite record of changing marine environments.

The technical scope of the study is formidable. The team analysed the lithostratigraphy and biostratigraphy of sections at Balingen-Zillhausen, Hechingen-Boll, Jungingen and Hechingen-Beuren, spanning the interval from the topmost Opalinuston Formation at the end of the Lower Aalenian to the basal Wedelsandstein Formation at the dawn of the Bajocian. Forty-one samples taken in 2018 and 2019, supplemented by material collected as far back as 1988, yielded approximately 4,100 ostracod specimens. After careful counting, the researchers identified 108 species, with 329 specimens remaining undetermined. Three new species were formally described: Cytheropterina crassicostata, named for its coarse, rounded ribs; Eucytherura eberti, honouring the palaeontologist Martin Ebert; and Eucytherura foveolata, distinguished by the characteristic pits dotting its lateral surface.

The new species are small but technically distinctive. Cytheropterina crassicostata, at just over half a millimetre long, bears a subtriangular carapace with broad, softly rounded ribs and a smooth underside to its wing-like extension, setting it apart from related forms like Cytheropterina bicuneata. Eucytherura eberti, barely a third of a millimetre, shows broad, smooth ribs running longitudinally across a weakly reticulate surface, with a row of small elongate pits above the muscle-scar field. Eucytherura foveolata carries a fine median rib flanked by shallow pits roughly fifteen micrometres wide, with four rhomboidally grouped pits in the mid-dorsal area providing a particularly striking signature. Ten additional taxa were figured but left in open nomenclature because they were found only in numbers of one to five specimens and could not be confidently assigned to any known genus.

What makes the ostracod record especially powerful is its sensitivity to change. The assemblages shift markedly at several key horizons: at the base of the Lower Aalenian Comptum Subzone, at the boundary between the Bradfordensis and Gigantea subzones, at the Bradfordensis-Concavum zonal boundary, and most dramatically at the Aalenian-Bajocian transition, where the Concavum Zone gives way to the Discites Zone. A minor turnover also occurs above the Calceola-Bank within the Concavum Zone. In the Concavum Zone alone, 34 species appear for the first time, and the total number of genera climbs from seven in the Bradfordensis Zone to twenty in the Gigantea Subzone and twenty-nine in the Concavum Zone. The cytherurid family shows the most striking development, with five new species appearing in the Gigantea Subzone and fourteen in the Concavum Zone.

The ammonite story is equally compelling. The Upper Aalenian faunas of the region are dominated by the Graphoceratidae, a family whose evolution unfolded as a gradual chronocline from the earliest Aalenian into the earliest Bajocian. Rather than representing a parade of distinct genera, the graphoceratid ammonites form a plexus of morphologies in which individual forms sometimes persist across long intervals while the overall character of successive faunas shifts steadily. The researchers found Graphoceras and Brasilia morphologies coexisting in single beds, accompanied by specimens blending characters of both. The team determined the ammonites conventionally as morphogenera and morphospecies, but concluded that all graphoceratids from the cavatum horizon probably represent a single palaeobiospecies whose variation changed through time.

The beds themselves tell a story of shifting sea-floor conditions. The Inopernabank, named after the bivalve Inoperna sowerbyana, contains large Pholadomya in life position and marks the uppermost Gigantea Subzone. The Konglomeratbank, a grey marly limestone packed with pebbles, and the Calceolabank, named for the masses of the small oyster Gryphaea calceola embedded chaotically in its lower part, both belong to the Concavum Subzone. The Calceolabank in particular yielded well-preserved ammonites including Graphoceras cavatum, G. concavum, G. fallax, G. decorum, G. pulchrum and G. formosum, alongside Brasilia decipiens and the microconch Ludwigella arcitenens. The overlying Rostrote Kalkbank, with its rusty-red weathering crust, completes the cavatum biohorizon, which the team formally introduced for the basal Concavum Zone of the region.

Correlating these faunas with other areas reveals a connected Jurassic world. Thirty-three genera and species from the study are also known from the English, Scottish and Irish Aalenian and Lower Bajocian, indicating a marine connection across the Paris Basin. The cavatum biohorizon of the Zollernalb can be matched directly with the cavatum biohorizon of Dorset in southwest England, where Chandler had previously documented the evolution of the Graphoceratidae at Horn Park Quarry. Species such as Cytherella apostolescui, Eocytheridea lacunosa and Procytherura multicostata tie the German sections to coeval faunas from England, France, Spain, Switzerland and even Argentina, where Aalenian ostracods have been described from the Fastnet Basin and the Neuquén Basin respectively.

The macrofauna adds further texture to the picture. Gryphaea calceola, first described from the vicinity of Jungingen, which is therefore considered its type locality, occurs in masses in the Calceolabank but as isolated valves in chaotic arrangement rather than in life position, suggesting storm reworking. Small specimens in other beds probably represent ecophenotypes that never reached maximum size under less favourable conditions. Byssate bivalves like Mytiloceramus polyplocus, recorded only from the Rostrote Kalkbank, may have lived attached to driftwood or empty ammonite shells in a pseudoplanktonic lifestyle. A single tooth of the shark Asteracanthus personati, found in the Zillhausen Member of the Starzel river, stands as the only vertebrate remain from the studied sections, while tanaidacean arthropod remains, once misidentified as tiny salamanders by Friedrich von Huene, occasionally surface in the Upper Aalenian claystones.

The integrative power of combining ammonite and ostracod biostratigraphy is the study’s greatest legacy. Where ammonites are absent or rare, ostracods can carry the stratigraphic signal, and vice versa, allowing significantly improved correlations between sections and across regions. The Heiligenbach section and the Geisingen clay pit together yielded 115 species from the Upper Aalenian, thirty-one of them recorded in both sections, a diversity far exceeding what was previously known for the interval in southwest Germany. The discovery that the lower boundary of the Levata ostracod zone must be shifted downward, and that Kinkelinella triangula appears directly at the base of the Lower Bajocian, refines the regional zonal scheme. For a stage that has long lived in the shadow of its more famous Toarcian and Bajocian neighbours, the Aalenian of the Zollernalb is finally getting its due.

Subject of Research: New records of ostracods and ammonites from the Aalenian (mainly Concavum Zone) of the Zollernalb (Swabian Alb, SW Germany)

Article Title: New records of ostracods and ammonites from the Aalenian (mainly Concavum Zone) of the Zollernalb (Swabian Alb, SW Germany)

Article References: Wannenmacher, N., Dietze, V., Franz, M., & Schweigert, G. (2021). New records of ostracods and ammonites from the Aalenian (mainly Concavum Zone) of the Zollernalb (Swabian Alb, SW Germany). Zitteliana, 95, 1-55. https://doi.org/10.3897/zitteliana.95.56296

Image Credits: AI Generated

DOI: 10.3897/zitteliana.95.56296

Keywords: paleontology, ostracods, ammonites, Jurassic, stratigraphy, Germany, fossils, records, Aalenian, mainly, Concavum, Zone

The research, carried out by Andri Degiacomi, Susanne Feist-Burkhardt and Stephan Wohlwend, combined classical sedimentological fieldwork with a technique rarely applied to such reef limestones: palynology, the study of organic microfossils, in this case the resistant cysts produced by ancient dinoflagellates, single-celled plankton that drifted in the Jurassic seas. Four stratigraphic sections, two on the Gisliflue ridge and two on the Homberg, were sampled and analysed in detail. The well-preserved dinoflagellate cyst assemblages recovered from many of the samples allowed the team to date the entire reef complex, together with a peculiar overlying deposit known in the Swiss literature as the Echinodermenbrekzie, to the Early Bajocian stage of the Middle Jurassic, specifically the Humphriesianum ammonite Zone.

The reef itself tells a vivid story of growth and death on a shallow sea floor. In its lower part, the researchers documented marly, strongly arenitic limestone containing isolated platy corals, evidence of a phase in which coral colonies were still sparse and sediment input relatively high. Upward, the facies changes dramatically: rock-forming platy corals of the genera Isastrea and Thamnasteria come to dominate, building the massive, resistant frame that now forms the striking cliffs, up to 20 to 40 metres high, that give the Gisliflue its silhouette above the Aare valley. At the very top of the summit, the final few metres are dominated mainly by branching corals, a shift that may reflect changing environmental conditions as the reef approached sea level.

The end of reef growth is recorded in a feature that palaeontologists find particularly evocative: a bored hardground capping the summit. A hardground is a seafloor surface that became cemented while exposed at or near the sediment-water interface, and the borings that riddle it were made by organisms excavating into the cemented surface in the earliest interval following the end of coral growth. In other words, the summit of the Gisliflue preserves a fossilised snapshot of the moment the reef finally stopped growing, a cemented sea floor colonised immediately by hard-substrate dwellers before the next phase of deposition began.

Tracing the bioherm laterally proved just as informative as dating it. The reef body can be followed westward across the ridge to the midsection of the Homberg, where it abruptly wedges out and passes into an arenitic, bioclastic limestone. This coarse, echinoderm-rich rock, packed with fragments of crinoids, sea urchins and other echinoderms, continues to the western end of the Homberg, where it maintains a fairly constant thickness of around 8 to 12 metres. This stratigraphic succession, long recognised both in the published literature and on official geological maps as the Echinodermenbrekzie, or echinoderm breccia, is thus shown to be the lateral equivalent of the coral reef rather than an unrelated unit stacked above it.

Regional comparisons with neighbouring stratigraphic sections add a further dimension to the picture. The analyses indicate a gradual lateral thinning of the Echinodermenbrekzie to the west, suggesting that the coarse bioclastic facies was deposited in a belt that tapered away from the reef margin. Such geometry is typical of reef-flank and fore-reef settings, where wave action and currents break up reef-dwelling organisms, especially the delicate echinoderms, and redistribute the debris as aprons of bioclastic sand and rubble flanking the living reef. The new data therefore tie the breccia genetically to the Gisliflue Reef, resolving a relationship that had remained ambiguous in the regional stratigraphy.

The palynological results carry implications well beyond the two ridges themselves. Because the reef and the Echinodermenbrekzie are dated to the Early Bajocian Humphriesianum Zone, while the oolitic limestones of the Hauptrogenstein that directly overlie the bored hardground at the summit are dated to the Late Bajocian Niortense Zone, the succession at Gisliflue now provides a tightly bracketed reference section for the Early to Late Bajocian transition in northern Switzerland. The Hauptrogenstein, a formation of oolitic limestones deposited in agitated, shallow water and famous as a building stone across the region, rests directly on the hardground, meaning the hiatus between reef growth and oolite deposition can be constrained to a narrow interval of ammonite zones.

A highlight of the study is the formal description of a new dinoflagellate cyst species, Hypolytodinium argoviense, designated as a new genus and new species. The species is considered a useful stratigraphic marker for the late Early Bajocian Humphriesianum Zone, with its main occurrence in the Romani to Humphriesianum subzones. Marker species of this kind are the workhorses of biostratigraphy: because dinoflagellate cysts evolved rapidly and dispersed widely, their first and last appearances allow sedimentary successions to be correlated over large distances, even in rocks, such as these reef limestones, that lack the ammonite fossils traditionally used to define Jurassic zones.

For the stratigraphy of northern Switzerland, the consequences are substantial. The Gisliflue Reef and its associated deposits had previously been assigned to various levels within the regional rock classification, and the new dating demonstrates that the reef complex, the Echinodermenbrekzie and the overlying Hauptrogenstein form a coherent, precisely dated succession spanning the Early to Late Bajocian. This allows geologists to refine the boundaries of lithostratigraphic units on maps and in the subsurface, where the same Jurassic rocks are encountered in boreholes and are relevant to groundwater flow, geothermal exploration and the assessment of potential nuclear waste repository host rocks in the region.

The study also illustrates how modern microfossil techniques can rejuvenate classic field localities. The cliffs of the Gisliflue have been examined for well over a century, yet the application of detailed dinoflagellate cyst stratigraphy has extracted a chronological framework that field observation alone could never deliver. As the authors show, a ridge of coral limestone above the Aare valley, once a puzzle of conflicting age assignments, now stands as one of the most securely dated Middle Jurassic reef successions on the Swiss Plateau, a reference point against which the reefal and bioclastic limestones of the entire region can be calibrated.

Subject of Research: Palynological dating of the Middle Jurassic Gisliflue coral reef and its stratigraphic implications in northern Switzerland

Article Title: New palynological dating of the coral bioherm «Gisliflue Reef» and the implication for the stratigraphy of northern Switzerland

Article References: Degiacomi, A., Feist-Burkhardt, S., & Wohlwend, S. (2025). New palynological dating of the coral bioherm «Gisliflue Reef» and the implication for the stratigraphy of northern Switzerland. Swiss Journal of Geosciences, 118(1), Article 20. https://doi.org/10.1186/s00015-025-00490-x

Image Credits: AI Generated

DOI: 10.1186/s00015-025-00490-x

Keywords: Gisliflue Reef, palynology, dinoflagellate cysts, Bajocian, Jurassic, Switzerland, coral bioherm, Echinodermenbrekzie, Hauptrogenstein, stratigraphy, Humphriesianum Zone, biostratigraphy

Conodonts are the unsung heroes of Paleozoic stratigraphy. These animals, which swam in the oceans for roughly 300 million years before vanishing at the end of the Triassic, produced elements composed of calcium phosphate that are extraordinarily resistant to dissolution and evolved rapidly enough to serve as precise chronological markers. Because different species appear and disappear in a predictable succession, geologists can use their first and last occurrences to subdivide rock sequences into biozones that can be correlated across continents. In South China, this approach is especially powerful, as the region hosts three Global Stratotype Sections and Points, the internationally agreed golden spikes that define boundaries of geological time, including the Permian–Triassic boundary at Meishan.

The study area, known as the western Hubei–eastern Chongqing or WHEC region, sits along the northern margin of the South China Block, which during the Permian lay along the eastern edge of the Paleo-Tethys Ocean. Here, thick marine successions record dramatic environmental upheaval: the end-Guadalupian mass extinction, the eruption of the Emeishan Large Igneous Province, a major regression, and a subsequent deepening of the seafloor that allowed thick, organic-rich black shales to accumulate. These shales, belonging to the Dalong Formation, have recently been confirmed to hold substantial industrial-scale shale gas reserves, making them a prime target for unconventional hydrocarbon exploration. But without precise ages, geologists could not be certain whether the gas-rich horizons in different wells and outcrops were actually deposited at the same time.

To resolve this uncertainty, the researchers collected 127 limestone and calcareous mudstone samples from the Longmenba, Huangping, Tongmuyuan, Chenjiawan, and Longjingwan sections. In the laboratory, the samples were crushed and dissolved in dilute acetic acid over seven to ten days, with the residues sieved and then processed using heavy-liquid separation in lithium metatungstate solution to concentrate the dense conodont elements. The method is elegantly simple in principle but demanding in practice, particularly because siliceous and argillaceous rocks, which dominate parts of the Dalong Formation, respond poorly to acid processing. This is why the team focused on interbedded limestones and calcareous horizons that readily yield their fossil cargo.

The results were striking. From 38 productive samples, the team recovered more than 1,200 conodont specimens representing 17 species in four genera: Jinogondolella, Clarkina, Hindeodus, and Iranognathus. These assemblages allowed the recognition of a near-continuous succession of biozones spanning the late Wuchiapingian through the Changhsingian, the two stages that together make up the Lopingian, the final epoch of the Permian Period. The succession begins with Jinogondolella xuanhanensis in the uppermost Guadalupian strata and climbs through a series of Clarkina zones, from C. asymmetrica and C. leveni through C. guangyuanensis, C. transcaucasica, C. orientalis, and C. longicuspidata, before culminating in the C. wangi, C. subcarinata, C. changxingensis, and C. yini zones of the Changhsingian.

This zonal sequence closely matches the internationally calibrated framework established at the Meishan and other reference sections in South China, which means the WHEC strata can now be correlated with global standards. Critically, the first appearance of Clarkina wangi, the species whose debut officially defines the Wuchiapingian–Changhsingian boundary at the Meishan GSSP, was documented in the upper part of the Dalong Formation at both Longmenba and Huangping. This allowed the team to place the stage boundary within the upper Dalong Formation across the study area, with only minor local variations attributable to differences in sedimentary facies and fossil preservation. The Longmenba section emerged as the most complete record, offering the most confident placement of the boundary.

The most consequential finding, however, concerns the age of the shale gas sweet spot itself. By integrating the conodont zones with lithostratigraphic observations, the researchers demonstrated that the organic-rich, siliceous-shale interval in the lower Dalong Formation is temporally restricted to the late Wuchiapingian, corresponding mainly to the upper part of the Clarkina guangyuanensis Zone and extending into the C. orientalis Zone or the lowermost C. longicuspidata Zone. In other words, the gas-productive rocks were deposited within a narrowly defined window of geological time, before fully developed Changhsingian faunas appeared. Comparable age constraints from other gas-bearing sections in the region, including Shangsi, Maoershan, Zhuqiao, Shiligou, Ganxi, and Well Da 201, reinforce the picture that shale gas enrichment across the WHEC region was preferentially concentrated in this single late Wuchiapingian interval rather than scattered randomly through the Late Permian.

Why was this particular window so favorable for organic matter accumulation? The answer lies in a convergence of environmental conditions. Following the end-Guadalupian regression, renewed basin subsidence created deep-water depocenters in the Middle and Upper Yangtze region at approximately 258 million years ago. From that point until the end of the Wuchiapingian, the region experienced reduced input of terrestrial sediment, enhanced accumulation of biogenic silica, and persistent stratification of the water column, conditions that promote high productivity in surface waters and efficient preservation of organic matter on the seafloor. Oxygen isotope evidence from conodont apatite and brachiopod shells further suggests that the C. leveni and C. orientalis zones coincided with relatively cool climatic episodes, which may have enhanced vertical mixing and nutrient recycling, thereby boosting the biological pump that delivered organic carbon to the deep basin.

Adding another layer of intrigue, the late Wuchiapingian also overlaps with the waning eruptive phase of the Emeishan Large Igneous Province. High-precision geochronology constrains the main phase of Emeishan volcanism to between roughly 260.55 and 257.22 million years ago, and evidence of continued activity during the Wuchiapingian comes from volcanic ash layers within the lower Dalong Formation itself, as well as from correlated sections across the region. The authors are careful to note that temporal overlap alone does not prove causation. Basin deepening and the associated paleoceanographic conditions likely exerted the primary control on organic matter enrichment, while volcanism may have acted as a secondary modulating factor, influencing climate, weathering fluxes, nutrient delivery, and silica cycling in ways that indirectly enhanced the conditions favorable for organic-rich shale formation.

Beyond its implications for energy exploration, the study showcases the enduring power of micropaleontology to solve practical problems. The absence of conodonts in two of the five studied sections, Chenjiawan and Longjingwan, was itself informative, pointing to facies-controlled preservational bias rather than true stratigraphic gaps, since siliceous sediments resist acid processing and some settings simply did not host conodont animals. By demonstrating that the WHEC succession is broadly continuous across the Guadalupian–Lopingian transition, punctuated only by a hiatus linked to the Dongwu tectonic uplift, the research provides a robust chronostratigraphic foundation for correlating shale-gas-favorable horizons across wells and outcrops. In doing so, it transforms a collection of tooth-like microfossils, each barely visible to the naked eye, into a precision clock for one of the most economically significant rock units in southern China, and a reminder that some of the biggest answers in Earth science come from its smallest remains.

Subject of Research: Late Permian conodont biostratigraphy of the Dalong Formation in western Hubei–eastern Chongqing, South China, and its implications for shale gas exploration

Article Title: Latest Guadalupian to Lopingian conodonts from western Hubei–eastern Chongqing, South China

Article References: Zhou, B., Wu, K., Song, T., Xu, L., Duan, K., Yuan, J., Yang, L., Zhao, B., Li, J., Wang, D., & Yang, B. (2026). Latest Guadalupian to Lopingian conodonts from western Hubei–eastern Chongqing, South China. Journal of Micropalaeontology, 45(1), 377-403. https://doi.org/10.5194/jm-45-377-2026

Image Credits: AI Generated

DOI: 10.5194/jm-45-377-2026

Keywords: conodonts, Late Permian, Lopingian, Wuchiapingian, Changhsingian, Dalong Formation, South China, biostratigraphy, shale gas, Emeishan Large Igneous Province, Clarkina, stratigraphy

Wright was, by any measure, a second-tier figure in the scientific hierarchy of his day. An autodidact who never held a university post, he earned his living through teaching and lecturing, yet he was fully plugged into the scientific conversations of his era. The manuscript analyzed by Tanner and Harper reveals a mind grappling with the central geological puzzles of the eighteenth century: how did the layered rocks that dominate the landscape come to be arranged as they are, and what did their arrangement imply about the age of the world? His answers were a curious but revealing blend of ideas that were already circulating among natural philosophers, combined with original speculations that anticipated, in some respects, debates that would only be resolved generations later.

At the heart of Wright’s scheme was a distinction between two kinds of strata. Horizontal layers of rock, he argued, were volcanic in origin, laid down by eruptive processes. This placed him firmly in the camp of the Plutonists, the faction of geologists who attributed many rock formations to the action of heat and fire, in opposition to the Neptunists, who explained nearly all rocks as precipitates from a primordial ocean. Wright’s commitment to a volcanic origin for horizontal strata is significant, because it shows that Plutonist thinking was not solely the invention of Hutton, whose famous Theory of the Earth appeared in 1788, just two years after Wright’s death. The manuscript demonstrates that volcanic explanations for layered rocks were part of the intellectual undercurrents well before Hutton’s paradigm-changing paper.

Inclined and vertical strata posed a harder problem, and here Wright reached for an older and stranger concept: the vegetative growth of minerals. In his model, mountains literally grew from small stones, emerging from the sea over immense stretches of time. As these growing mountains rose above the water, they pushed previously horizontal volcanic strata into inclined or even vertical orientations. The image is one of a dynamic, evolving planet in which topography is not fixed but develops through organic-like processes, with rock masses behaving almost like living tissue. The idea of mineral vegetation sounds bizarre to modern ears, but in the eighteenth century it was a serious proposal, rooted in the observation that crystals grow and that ores seem to form within rock cavities over time.

One of the most striking features of Wright’s model is how he accounted for fossils on mountaintops. As his growing mountains emerged from the sea, he proposed, they acquired a layer of shells belonging to marine animals. Those shells were subsequently carried upward and came to rest on the summits of mountains, explaining why fossilized marine creatures are found at high elevations. This was a genuine geological problem of the era: the presence of sea shells embedded in rocks on alpine peaks had puzzled thinkers for centuries and had been interpreted by some as evidence of Noah’s Flood. Wright’s mechanism, while mechanically implausible, at least sought a naturalistic, process-based explanation rather than a single catastrophic deluge, reflecting the gradual shift toward uniform, law-governed accounts of Earth history.

Wright went further and used the degree of petrification of these fossil materials as a kind of geological clock. By assessing how thoroughly organic remains had been converted to stone, he concluded that the age of the Earth was substantially greater than the few thousand years allowed by a literal reading of biblical chronology. This was a bold inference. In the 1780s, most scholarly estimates of the Earth’s age, even relatively generous ones, remained within the range of a few thousand to a few tens of thousands of years. Wright’s willingness to push beyond that framework marks him as one of the voices arguing for a far more ancient planet, decades before the accumulation of stratigraphic evidence would make deep time a scientific commonplace.

His cosmological speculations carried the argument to an even more astonishing extreme. Wright believed that the planets of the Solar System represented bodies at different stages of a common evolutionary cycle, with Saturn the youngest and Mercury the oldest. Each planet, in his scheme, was born, evolved, and eventually perished, and the Earth was simply one participant in this grand sequence. Working out the timescales implied by such a cycle, Wright concluded that at least a trillion years, 10^12 years, would be necessary for the full passage from creation to destruction of a planet. Modern science dates the Earth to about 4.54 billion years, so Wright’s figure overshoots by more than two orders of magnitude, but the conceptual leap is breathtaking: he was proposing timescales for planetary evolution that dwarf anything contemplated by his contemporaries, and he tied the history of our planet to a life-cycle model of the cosmos as a whole.

Tanner and Harper are careful to place Wright’s ideas in their proper intellectual genealogy. His overall model of the origin and evolution of the Earth was heavily influenced by the writings of Thomas Burnet, whose Sacred Theory of the Earth had imagined the planet as a transformed, degraded version of an originally smooth sphere, and of William Whiston, who had linked geological change to cometary encounters. But the stratigraphic specifics, the volcanic strata, the growing mountains, the shells on the summits, were drawn from the later debates on the origin of strata and their fossils that animated natural philosophy through the middle and late eighteenth century. The manuscript thus serves as a document of transition, capturing the moment when cosmological speculation was beginning to give way to observationally grounded geology.

Perhaps the most historically poignant aspect of the manuscript is its timing. Wright’s work precedes the publication of James Hutton’s observations of unconformities, those surfaces within rock sequences that record gaps of immense duration, and the profound implications of those unconformities for the age of the Earth. Hutton’s insight, that such breaks in the stratigraphic record require cycles of deposition, uplift, and erosion repeated over unimaginable spans of time, is often presented as the decisive break with scriptural chronology. Wright’s manuscript shows that the ground was already shifting. The undercurrents of debate about strata, fossils, and deep time were swirling through the scientific community, and even a self-taught lecturer in Durham was constructing models of planetary evolution that required trillions of years. The study by Tanner and Harper reminds us that scientific revolutions are rarely the work of a single mind; they emerge from a ferment of ideas in which second-tier thinkers, working at the margins, help prepare the intellectual soil for the transformations to come.

Subject of Research: The stratigraphic ideas and age-of-the-Earth estimates in Thomas Wright of Durham's unpublished eighteenth-century manuscript

Article Title: Strata super strata: the stratigraphy of Thomas Wright of Durham (1711–1786)

Article References: Tanner, B. K., & Harper, D. A. T. (2026). Strata super strata: the stratigraphy of Thomas Wright of Durham (1711–1786). https://doi.org/10.5194/hgss-2026-17

Image Credits: AI Generated

DOI: 10.5194/hgss-2026-17

Keywords: Thomas Wright of Durham, stratigraphy, history of geology, Plutonism, age of the Earth, deep time, James Hutton, unconformities, fossils, mountain building, eighteenth century, History of Geo- and Space Sciences

The commentary, authored by researchers at the Max Planck Institute of Geoanthropology, does not contest the right of the IUGS to reject the proposal. Lead author Georg Schäfer is explicit on this point: a proposal can legitimately be rejected, and scientific bodies routinely decline candidate units on well-documented grounds. What concerns the authors is something different and, they argue, more corrosive. No adequate scientific justification for the rejection was ever published, they contend, and serious allegations of procedural inconsistencies remain unaddressed. In their view, the legitimacy of the decision rests not on whether the Anthropocene was approved or declined, but on whether the process that produced the outcome met the standards the geological community itself has established.

The procedural concerns documented in the paper are specific and technical. According to the authors, the evaluation of the Anthropocene Working Group’s proposal was compromised in a fundamental way: the working group was unable to address reviewer comments or make revisions to its submission before a decision was reached. In standard scientific practice, whether in peer review or in formal stratigraphic ratification, the opportunity to respond to criticism and refine a case is considered essential to fair evaluation. Removing that opportunity, the commentary argues, undermines the evidentiary basis on which the final judgment could claim scientific authority. A decision made without the possibility of revision, the authors suggest, is a decision about a document that its own authors could not defend or improve.

Equally troubling, the paper reports, was the voting process itself. The majority of votes cast in the decision were, by the IUGS’s own rules, invalid. In a body whose authority derives from adherence to its established statutes and procedures, an outcome determined substantially by votes that should not have counted presents a genuine problem. The commentary frames this not as a minor administrative slip but as a structural failure: if the rules governing ratification are not applied to the ratification itself, the resulting decision inherits a legitimacy deficit that no amount of subsequent communication can fully repair. The authors emphasize that these are not speculative grievances but documented irregularities that have never been formally resolved in public.

Adding to the concern is the fate of an internal ethics report. According to the commentary, an internal investigation was conducted into the procedural violations surrounding the decision, and the IUGS executive committee did not act upon its findings. That report, the authors note, remains publicly inaccessible. For a decision of this magnitude, one that determines whether the formal geological timescale will or will not recognize humanity’s planetary impact, the withholding of the investigative record strikes the authors as incompatible with the transparency that scientific governance requires. They call on the IUGS to fully disclose the relevant documentation and to submit the decision to an independent procedural review.

The stakes, the authors insist, extend well beyond the internal politics of a scientific union. Professor Jürgen Renn, founding director of the Max Planck Institute of Geoanthropology, argues that the Anthropocene epoch proposal demands transparency and procedural legitimacy precisely because of what it represents. If decisions regarding a humanity-induced planetary crisis can be made behind closed doors, with key documents withheld and public communication vague or contradictory, then geoscience’s capacity to inform societal understanding of Earth system change is diminished. In Renn’s framing, the question is not merely whether geologists label a slice of time correctly, but whether the institutions that steward Earth science can be trusted to communicate honestly with a public facing accelerating environmental change.

That broader significance is easy to underestimate. Since its introduction in 2000, the Anthropocene concept has become one of the most influential ideas in modern science, spreading from the geosciences into culture, law, economics, and the humanities. It has shaped debates about climate policy, biodiversity governance, and legal accountability for environmental harm. Courts, museums, curricula, and international assessments have all absorbed the term. The formal rejection of the Anthropocene as a geological epoch does not erase this influence, but it does create a gap between the scientific formalization of the concept and its social life. How that gap is explained to the public matters, and the commentary suggests that an opaque process makes the explanation harder, not easier.

The technical substance of the rejected proposal deserves attention in its own right. The Anthropocene Working Group spent more than a decade identifying candidate markers for a formal epoch, settling on Lake Crawford in Ontario, Canada, where annually laminated sediments preserve an exceptionally clear record of the mid-twentieth century. Plutonium isotopes from atmospheric weapons testing, fly ash from fossil fuel combustion, and a suite of other anthropogenic signals appear in the lake’s layers with striking synchronicity, offering the kind of globally correlatable boundary marker that stratigraphic classification demands. The working group’s case was, by the standards of formal chronostratigraphy, carefully constructed. That construction, and the years of coring, analysis, and debate behind it, is part of what makes the procedural questions surrounding its rejection so consequential for the researchers who produced it.

The commentary also speaks to a wider tension in contemporary science governance: the boundary between scientific judgment and institutional strategy. The title of the paper, Science or Strategy? The Rejection of the Anthropocene Epoch Demands Transparency, poses the question directly. Was the rejection grounded in a published, defensible scientific assessment of the stratigraphic evidence, or was it shaped by institutional considerations, including discomfort with the societal and political implications of formally declaring a human-dominated epoch? The authors do not claim to answer that question. Their point is that the question cannot be answered at all under current conditions of restricted documentation and unaddressed allegations, and that this unanswerability is itself the problem.

What the researchers are asking for is deliberately modest in mechanism and far-reaching in implication. They want the IUGS to release the documentation relevant to the decision, including the internal ethics report, and to commission an independent review of the procedures that produced the outcome. Such steps would not reopen the question of whether the Anthropocene should be ratified; they would establish whether the process met the union’s own standards. If the review vindicated the decision, the geological community could move forward with confidence. If it identified failures, the union would have the opportunity to correct its practices before the next consequential judgment arrives. Either way, the authors argue, transparency would strengthen rather than weaken the institution. At a moment when public trust in expert institutions is fragile and the stakes of Earth system science have never been higher, the treatment of a single epoch proposal may prove to be a test case for how the geosciences govern themselves in the Anthropocene, whatever the timescale ultimately decides to call it.

Subject of Research: Procedural transparency in the IUGS rejection of the Anthropocene epoch proposal

Article Title: Science or strategy? Researchers call for transparency over the Anthropocene rejection

Article References: Science or strategy? Researchers call for transparency over the Anthropocene rejection. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Anthropocene, IUGS, geology, stratigraphy, procedural transparency, Max Planck Institute of Geoanthropology, Earth's Future, Lake Crawford, scientific governance, epoch proposal, peer review, Earth system science

The technical heart of the argument lies in fallout from above-ground thermonuclear weapons testing. Beginning in the early 1950s, detonations of high-yield fusion devices injected artificial radionuclides into the stratosphere, from where they settled onto land, ice and ocean in a thin, worldwide veneer. Among these products, plutonium isotopes show a sharp global upturn in 1952, and because plutonium has no natural source in recent surface environments and is comparatively immobile once deposited, it functions as an exceptionally clean primary marker. In annually laminated lake sediments such as those of Crawford Lake in Ontario, Canada, the proposed golden spike locality, the plutonium rise can be pinned to a single annual varve, allowing correlation between archives worldwide with an uncertainty of a year or two, a precision almost unheard of in the deeper geological record.

Crucially, the plutonium signal does not stand alone. The researchers document what they call the Great Acceleration Event Array, a cluster of mid-century physical, chemical and biological signals that appear together in sediments across both hemispheres and every climatic belt. Spheroidal carbonaceous particles, microscopic spheres of elemental carbon produced only by burning coal and fuel oil at high temperature, appear in peat bogs, lake muds, coral skeletons and even an Antarctic ice core. Stable carbon and nitrogen isotopes shift as fossil fuel combustion and industrial fertiliser transformed the planet’s carbon and nitrogen cycles. Heavy metals including lead, mercury and arsenic climb sharply, plastic debris begins its geological journey, and invasive species restructure biological communities from the Baltic Sea to San Francisco Bay.

The scale of the underlying Earth system change is quantified with sobering figures. Atmospheric carbon dioxide now stands 51 percent above typical Holocene concentrations, while methane has risen 157 percent, driving global mean temperatures roughly 1.5 degrees Celsius above pre-industrial levels. Ice cores show that greenhouse gas levels remained within a narrow band for most of the past 11,700 years, the span of the Holocene Epoch, making the current departure both rapid and unusual when viewed against three decades of millennia of natural variability. The authors argue that these shifts overwhelm the regulatory feedbacks that previously stabilised the Earth system, and that this planetary threshold is exactly what an epoch boundary should record.

The choice of 1952 also serves a stratigraphic logic that goes beyond convenience. Earlier candidates for the start of the Anthropocene, such as the onset of agriculture millennia ago, the Columbian exchange of the sixteenth century or the Industrial Revolution of the late eighteenth century, produce signals that are diachronous, meaning they appear at different times in different places, and are often subtle or locally overprinted. By contrast, bomb fallout arrived essentially everywhere at once. The team acknowledges a rich pre-history of human impact, from early mining lead anomalies to deforestation, but insists that these belong to the characterisation of the Holocene, an epoch in which human influence, however real, never tipped the planetary machinery into a new state.

Formal recognition would require a Global boundary Stratotype Section and Point, the so-called golden spike, and Crawford Lake has been proposed for that role. Its sediments accumulate in varves, paired seasonal layers that permit year-by-year dating, and its small, sheltered basin records fallout with minimal disturbance. Supporting auxiliary sections, including Sihailongwan Maar Lake in northeastern China, Searsville Lake in California, Beppu Bay in Japan, the Palmer ice core from the Antarctic Peninsula, corals from Flower Garden Banks and North Flinders Reef, the Baltic Sea’s East Gotland Basin, a peatland at Śnieżka in Poland, the Ernesto Cave stalagmite in Italy and urban sediments at Vienna’s Karlsplatz, would anchor the boundary across marine, terrestrial, tropical and polar settings.

Not everyone is convinced, and the article engages frankly with the opposition. In 2024, the International Union of Geological Sciences declined to ratify the Anthropocene as an epoch, with critics arguing that the term works better as an informal concept or as a diachronous geological event rather than a precisely timed unit. Some have questioned whether an epoch lasting mere decades is proportionate to units that typically span millions of years. Waters and colleagues respond that geological units are defined by the quality of their boundary signals, not their duration, that the geological record is replete with brief intervals, and that the Anthropocene’s global synchronicity and uniqueness actually exceed the criteria applied to many ancient boundaries.

The stakes extend well beyond taxonomy. The authors argue that placing the Anthropocene on the Geological Time Scale would give scientists, educators and policymakers a common, rigorously defined reference point for the scale and abruptness of human-driven planetary change. It would confine the Holocene to its true character as an interval of unusual climatic stability, and would provide a unifying framework across disciplines from stratigraphy and ecology to Earth system science, in which the Anthropocene term is already used widely but inconsistently. Future geologists, they suggest, will encounter this interval whether or not it is formally named; the question is whether the present generation chooses to describe it with precision.

Whatever the formal outcome, the study reframes the Anthropocene from metaphor to measurement. By knitting together radionuclide fallout, industrial ash, isotope chemistry, microplastics, metals and biological invasions across a dozen independent archives, the researchers have assembled the kind of multi-proxy, globally correlated evidence that underpins every epoch boundary in the geological column. The plutonium horizon of 1952, they conclude, marks the moment humanity’s imprint became synchronous, permanent and unmistakable in the rocks, a stratigraphic signature distinct from everything that came before it in the Holocene.

The machinery behind formalising a new unit of geological time is deliberately slow and demanding. Under the guidelines of the International Commission on Stratigraphy, a candidate boundary must be fixed to a physical reference point in a rock, sediment or ice succession, and the marker chosen must be correlatable across environments as different as deep ocean basins and mountain glaciers. The plutonium fallout horizon satisfies this requirement in a way few markers ever have, because the same signal can be located in archives that preserve annual layers, giving geologists a common time line where older boundaries often carry uncertainties of thousands of years.

The comparison with the Holocene itself is instructive. That epoch was defined in 2009 using the NGRIP ice core in Greenland, with its base pinned to a climatic warming event recorded in ice chemistry. The proposed Anthropocene boundary follows the same logic but achieves finer resolution, since bomb-derived radionuclides can be measured at concentrations far below those of natural isotopes, and their abrupt appearance reflects a discrete historical process rather than a gradual climatic transition. This illustrates how the tools available to stratigraphers have expanded, allowing boundaries to be drawn with a precision that earlier generations of geologists could not have imagined.

The multi-proxy approach also guards against a familiar pitfall in correlation work: post-depositional alteration. Some radionuclides can migrate within sediments or soils, blurring a boundary in certain archives, which is why the authors pair the plutonium signal with particles and chemical shifts that are effectively immobile once buried. Spheroidal carbonaceous particles, for example, are preserved intact in peat and lake mud, while isotope shifts in carbon and nitrogen record the reorganisation of planetary biogeochemical cycles. When several independent signals align at the same level across a dozen archives, the likelihood that the alignment is coincidental becomes vanishingly small.

There is also a deeper scientific point about what the geological record preserves. Human activity has generated materials with no natural counterpart, from plastics to concrete to aluminium, and these are already accumulating in sediments that future investigators will treat exactly as present-day geologists treat ancient strata. Recognising the Anthropocene formally would simply bring the naming conventions of the time scale into line with what the sedimentary record is already registering, and would give the interval a defined base rather than leaving its start open to interpretation in every discipline that borrows the term.

Subject of Research: Stratigraphic evidence defining the Anthropocene as a formal geological epoch beginning in 1952.

Article Title: Defining the Anthropocene using precise geological evidence

Article References: Waters, C. N., Zalasiewicz, J., Turner, S. D., Head, M. J., McCarthy, F. M. G., Kuwae, M., Han, Y., Fiałkiewicz-Kozieł, B., Wagreich, M., DeLong, K. L., Kaiser, J., Borsato, A., Zinke, J., Williams, M., Thomas, E. R., Rose, N. L., Ivar do Sul, J. A., Gałuszka, A., Cundy, A. B., … Jeandel, C. (2026). Defining the Anthropocene using precise geological evidence. Nature Reviews Earth & Environment, 7(9), 612-632. https://doi.org/10.1038/s43017-026-00817-8

Image Credits: AI Generated

DOI: 10.1038/s43017-026-00817-8

Keywords: Anthropocene, stratigraphy, plutonium fallout, Crawford Lake, Geological Time Scale, golden spike, Holocene, Great Acceleration, thermonuclear testing, fly-ash particles, Earth system change, epoch definition