Micha Ruhl

Trinity College Dublin | TCD · Department of Geology

Extreme climate warmth (hyperthermal) events through deep-time offer prescient insights into how the Earth may respond to present-day warming related to greenhouse gas emissions. This special issue deals with Paleoenvironmental changes across the Mesozoic–Paleogene hyperthermal events and comprises 25 interdisciplinary research articles. In this re...

The end‐Triassic mass extinction is considered one of the “Big Five” extinction events in the Phanerozoic. However, whether the terrestrial ecosystem began to deteriorate or even collapse prior to the Triassic–Jurassic (Tr‐J) transition remains controversial. Compared with the documented data from the western Tethyan region, evidence from the easte...

The pulsed extinction of marine organisms during the latest Triassic (the end-Triassic mass extinction, ETME) represents one of the largest mass extinction events in geological history. The ETME is thought to have been driven by large igneous province volcanism which caused perturbations to ocean redox chemistry and surface temperatures. However, t...

Past large igneous province (LIP) emplacement is commonly associated with mantle plume upwelling and led to major carbon emissions. One of Earth’s largest past environmental perturbations, the Toarcian oceanic anoxic event (T-OAE; ~183 Ma), has been linked to Karoo-Ferrar LIP emplacement. However, the role of mantle plumes in controlling the onset...

One of the most severe extinctions of complex marine life in Earth’s history occurred at the end of the Triassic Period. The end-Triassic extinction event was initiated by large igneous province volcanism and has tentatively been linked to oceanic redox change. However, the global-scale pattern of oceanic redox across the end-Triassic event is not...

The past ~550 million years of Earth’s history have been marked by numerous periods of global extinction, one of the most severe of which took place at the end of the Triassic period (ETME). The ETME has been strongly assoicated with marine redox change. However, the global scale pattern of oceanic redox across the ETME is not well constrained....

The de-oxygenation of marine environments is thought to have played a significant role in many of Earth’s major mass extinction events. This includes the end-Triassic mass extinction event (ETME), which witnessed the disappearance of conodonts, the near extinction of ammonoids and the most significant reef crisis across the entirety of the Phaneroz...

The de‑oxygenation of marine environments is thought to have played a significant role in many of Earth's major mass extinction events. This includes the end-Triassic mass extinction event (ETME), which witnessed the disappearance of conodonts, the near extinction of ammonoids and the most significant reef crisis across the entirety of the Phaneroz...

The Pliensbachian–Toarcian boundary interval is characterized by a ~ 3‰ negative carbon-isotope excursion (CIE) in organic and inorganic marine and terrestrial archives from sections in Europe, such as Peniche (Portugal) and Hawsker Bottoms, Yorkshire (UK). A new high-resolution organic-carbon isotope record, illustrating the same chemostratigraphi...

The isotope ratios of redox-sensitive metals in organic-rich rocks are critical tools for quantifying the timing and severity of deoxygenation and nutrient cycling in Earth’s past. The resilience of isotopic data to thermal alteration of the host sediments over millions of years of burial is, however, largely unknown. We present molybdenum, uranium...

Fire regimes are changing due to both anthropogenic climatic drivers and vegetation management challenges, making it difficult to determine how climate alone might influence wildfire activity. Earth has been subject to natural-background climate variability throughout its past due to variations in Earth's orbital parameters (Milkankovitch cycles),...

The Pliensbachian–Toarcian boundary interval is characterized by a ~3‰ negative carbon-isotope excursion (CIE) in organic and inorganic marine and terrestrial archives from sections in Europe, such as Peniche (Portugal) and Hawsker Bottoms, Yorkshire (UK). A new high-resolution organic-carbon isotope record, illustrating the same chemostratigraphic...

The Tibetan Himalaya region provides crucial sedimentary successions for studying the evolution of the eastern Tethyan depositional area. However, the palaeo-environmental conditions during the Early Cretaceous period in southern Tibet (Tethys Himalaya northern zone) are not well constrained. In this paper, we report on the major, trace, and rare e...

Lower Jurassic sedimentary successions in the Atlantic margin basins include several organic-rich intervals, some with source rock potential; time-equivalent units are also identified in on- and offshore areas worldwide. Despite decades of research, it is still unclear which mechanisms lead to the deposition of organic-rich sediments during the Ear...

The leading hypothesis for the Toarcian oceanic anoxic event (T-OAE; ∼183Ma) and the associated negative C-isotope excursion is the massive release of ¹² C favouring greenhouse and continental weathering. The nutrient delivery to shallow-basins supported productivity and, because of O 2 -consumption by organic-matter respiration, anoxia development...

We here report a high-resolution organic C-isotope record from terrestrial–marine transitional sediments of the Badong Formation in Luojiagou section, Zigui Basin of Hubei Province, South China. Our organic carbon isotope (δ¹³Corg) profile, ranging from -21.2‰ to -26.2‰, shows four negative carbon-isotope shifts. We suggest that the sharpest negati...

The detailed assessment of high-resolution elemental and isotopic geochemical datasets collected from the marl-limestone alternations cropping out at La Cerradura (Subbetic domain of the Betic Cordillera, Spain) and chrono- and chemostratigraphic correlation with the reference Mochras borehole (Cardigan Bay Basin, UK) unveiled valuable new insights...

Despite increasing numbers of studies interpreting the end-Triassic mass extinction event (ETME) as being caused through global marine anoxia, there are currently few studies which present redox data from across the critical interval, nor high resolution redox studies, or studies which correlate redox and biodiversity data from the same site. H...

The organic-rich upper Lower Jurassic Da'anzhai Member (Ziliujing Formation) of the Sichuan Basin, China is the first stratigraphically well-constrained lacustrine succession associated with the Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma). The formation and/or expansion of the Sichuan mega-lake, likely one of the most extensive fresh-water syste...

The Central Atlantic Magmatic Province (CAMP) generated voluminous lava flows and numerous sills. Its emplacement coincided with the c. 201 Ma end-Triassic mass extinction and global warming[1]. CAMP sills, in particular, may have played a crucial role in the end-Triassic crisis by generating greenhouse and toxic gases (e.g., CH4, CO2, SO2) when th...

The end-Triassic extinction is one of the major Phanerozoic mass extinctions and it appears to have been linked to coeval rapid and severe environmental change, thought to be triggered by volcanism in the Central Atlantic Magmatic Province (CAMP). However, direct stratigraphic evidence to substantiate this linkage and help develop scenarios for the...

The Triassic–Jurassic transition interval is marked by enhanced biotic turnover rates in both marine and terrestrial realms. However, limited data from Asia hampers the understanding of global ecosystem response to the end-Triassic mass extinction event. Here, we present significant vegetation and climate changes across the Triassic–Jurassic transi...

Here we report on recent developments on geochemical proxies derived from belemnite rostra from Cabo Mondego section in Portugal. Cabo Mondego is stratigraphically significant outcrop as the location of the GSSP and Point for the Bajocian and the ASSP for the Bathonian. Belemnite rostra of 118 individuals from across the Bajocian–Bathonian boundary...

The Rhaetian (201–209 Ma, the latest stage of the Triassic) is an important time-interval for the study of environmental changes preceding the End-Triassic Mass extinction. A detailed sedimentological and chemostratigraphic study was conducted in the lower Kössen Formation at Hochalm (Austria), the type-section of the Hochalm Member (Mb). This sect...

Cores recovered from the Jurassic (Toarcian) Posidonienschiefer (Posidonia Shale) in the Lower Saxony Basin, Germany, contain calcite‐filled fractures (veins) at a low angle to bedding. The veins preferentially form where the shale is both organically rich and thermally mature, supporting previous interpretations that the veins formed as hydraulic...

Significance Cyclic variations in Earth’s orbit drive periodic changes in the ocean–atmosphere system at a time scale of tens to hundreds of thousands of years. The Mochras δ ¹³ C TOC record illustrates the continued impact of long-eccentricity (405-ky) orbital forcing on the carbon cycle over at least ∼18 My of Early Jurassic time and emphasizes o...

The isotopic composition of Cd buried in marine sediments may preserve valuable palaeoenvironmental information on past ocean redox conditions or biological cycling. It is unclear, however, how the Cd-isotope composition of the sedimentary record reflects these processes. In this study, new Cd-isotope data are presented, along with δ¹³C, and Cd, Mo...

Ammonites underwent an evolutionary diversification after the mass extinction of the end Triassic induced by the formation of a Large Igneous province (LIP), and this group provides the most useful marine biostratigraphy. Only two levels within the Jurassic are relatively well determined using U–Pb dating from single zircons in ash beds, at the bas...

Earth’s history has been dominated by the large-scale disappearances of life in catastrophic events known as ‘Mass extinctions’. Mass extinction events have been closely linked to the large-scale release of isotopically light carbon, e.g. from large volcanic provinces, which is believed to have resulted in atmospheric, climatic and environmental ch...

Cyclostratigraphy is an important tool for understanding astronomical climate forcing and reading geological time in sedimentary sequences, provided that an imprint of insolation variations caused by Earth’s orbital eccentricity, obliquity and/or precession is preserved (Milankovitch forcing). Numerous stratigraphic and paleoclimate studies have ap...

The Early Jurassic was characterized by major climatic and environmental perturbations which can be seen preserved at high resolution on orbital timescales. The Early Jurassic is a period of overall global warmth, and therefore serves as a suitable modern-day analogue to understand changes in the Earth System. Presently, Earth’s climate is warming...

The Early Jurassic was characterized by major climatic and environmental perturbations which can be seen preserved at high resolution on orbital timescales. The Early Jurassic is a period of overall global warmth, and therefore serves as a suitable modern-day analogue to understand changes in the Earth System. Presently, Earth’s climate is warming...

The Triassic‐Jurassic transition (~201.5 Ma) is marked by one of the largest mass extinctions in Earth's history. This was accompanied by significant perturbations in ocean and atmosphere geochemistry, including the global carbon cycle, as expressed by major fluctuations in carbon isotope ratios. Central Atlantic Magmatic Province (CAMP) volcanism...

Mercury (Hg) is increasingly being used as a sedimentary tracer of Large Igneous Province (LIP) volcanism, and supports hypotheses of a coincidence between the formation of several LIPs and episodes of mass extinction and major environmental perturbation. However, numerous important questions remain to be answered before Hg can be claimed as an une...

The Lower Jurassic Toarcian Stage (c. 183-174 Ma) is marked by one of the largest global exogenic carbon-cycle perturbations of the Phanerozoic, which is associated with the early Toarcian Oceanic Anoxic Event (T-OAE; c. 183 Ma). Climatic and environmental change at the T-OAE is reasonably well constrained in the marine realm, with marine anoxic or...

The late Early Jurassic Toarcian Stage represents the warmest interval of the Jurassic Period, with an abrupt rise in global temperatures of up to ∼7 °C in mid-latitudes at the onset of the early Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma). The T-OAE, which has been extensively studied in marine and continental successions from both hemispheres,...

The Toarcian Oceanic Anoxic Event (T-OAE, 183 Ma) was characterized by enhanced carbon burial, a prominent negative carbon-isotope excursion (CIE) in marine carbonate and organic matter, and numerous geochemical anomalies. A precursor excursion has also been documented at the Pliensbachian/Toarcian boundary, but its possible causes are less constra...

Oceanic Anoxic Event 2 (OAE 2), during the Cenomanian–Turonian transition (∼94 Ma), was the largest perturbation of the global carbon cycle in the mid-Cretaceous and can be recognized by a positive carbon-isotope excursion in sedimentary strata. Although OAE 2 has been linked to large-scale volcanism, several large igneous provinces (LIPs) were act...

Molybdenum (Mo)-isotope chemostratigraphy of organic-rich mudrocks has been a valuable tool for testing the hypothesis that the Toarcian Oceanic Anoxic Event (T-OAE, Early Jurassic, ~183 Ma) was characterized by the spread of marine euxinia (and organic-matter burial) at a global scale. However, the interpretation of existing Mo-isotope data for th...

Significance The end of the Triassic Period (∼201.5 million years ago) witnessed one of the largest mass extinctions of animal life known from Earth history. This extinction is suggested to have coincided with and been caused by one of the largest known episodes of volcanic activity in Earth’s history. This study examines mercury concentrations of...

The end-Triassic is characterized by one of the most severe biotic crises of the entire Phanerozoic, with strong carbon cycle perturbations potentially predating the biotic event. In order to improve and test the chemostratigraphic framework for the Rhaetian Stage, which culminated in the end-Triassic extinction, a total of 675 and 108 carbonate δ1...

The Posidonienschiefer (Early Jurassic, ∼183 Ma) is the expression of the Toarcian Oceanic Anoxic Event (T- OAE) in Germany and Northern Switzerland and comparable to its correlative units in the UK (Jet Rock) and France (Schistes Carton) is composed of organic-rich, laminated clayey and calcareous mudstone. The carbon iso- tope record is marked by...

The Early Jurassic Toarcian oceanic anoxic event (∼183 Ma) was marked by marine anoxia–euxinia and globally significant organic-matter burial, accompanied by a major global carbon-cycle perturbation probably linked to Karoo–Ferrar volcanism. Although the Toarcian oceanic anoxic event is well studied in the marine realm, accompanying climatic and en...

The Early Jurassic (ca 201 to 174 Ma) was marked by a series of rapid perturbations in climate, the environment and global geochemical cycles, which have been linked to volcanic outgassing and the release of biogenic or thermogenic methane into the ocean–atmosphere system. The state of the global carbon cycle and prevailing climatic and environment...

Early Jurassic marine palaeotemperatures have been typically quantified by oxygen-isotope palaeothermometry of benthic and nektonic carbonate and phosphatic macrofossils. However, records of Early Jurassic sea-surface temperatures that can be directly compared with general circulation model simulations of past climates are currently unavailable. Th...

Oceanic Anoxic Event 2 (Cenomanian–Turonian: ca 94 Ma) represents a major palaeoceanographic phenomenon that took place during an interval of extreme global warmth when large amounts of organic matter entered the marine burial record, probably triggered by increased availability of nutrients for planktonic biota. Three sections (Eastbourne, Sussex,...

A high-resolution palynological study of the Triassic–Jurassic boundary in the St. Audrie's Bay section revealed a palynofloral transition interval with four pronounced spore peaks in the Lilstock Formation. Regular cyclic increases in palynomorph concentrations can be linked with periods of increased runoff, and correspond to the orbital eccentric...

The Jurassic (~201–145 Myr ago) was long considered a warm ‘greenhouse’ period; more recently cool, even ‘icehouse’ episodes have been postulated. However, the mechanisms governing transition between so-called Warm Modes and Cool Modes are poorly known. Here we present a new large high-quality oxygen-isotope dataset from an interval that includes p...

Supplementary Figures 1-2, Supplementary Tables 1-2 and Supplementary References

Oxygen and carbon isotope data, selected element ratios, location, age, and fossil identification. New and previously published data are included.