Periodic Reporting for period 1 - RECOVERY (Response of Earth system to extreme palaeoclimatic and palaeoenvironmental changes: A multiproxy study of the aftermath of the Toarcian hyperthermal)
Okres sprawozdawczy: 2021-01-18 do 2023-01-17
Climate change is currently one of the major challenges for our society. It has become urgent to understand the stabilization and recovery patterns of Earth’s climate system from extreme events to find mitigation and adaptation solutions. However, to date our knowledge on the natural capacity of Earth’s system to recover through long-term carbon storage processes is still limited. By placing current climate warming in the context of past extreme climate changes it is possible to get concrete observations and quantification from natural examples at different time scales. RECOVERY aims to fill this gap by providing a holistic understanding on how the Earth’s system can recover and stabilize over longer time scales.
Earth’s climate history has been punctuated by several warming events that were often associated with fast increase in atmospheric greenhouse gas levels linked to the onset of large-scale volcanism. The Toarcian Oceanic Anoxic Event (TOAE, Early Jurassic) was one of the most extreme hyperthermal events in Earth history and can hence provide keys on how biogeochemical cycles have controlled Earth’s carbon cycle-climate dynamics over geological time scales. Taking the TOAE as a case study, RECOVERY aims to better understand the causes and feedback mechanisms that can enable the Earth’s system to recover and to adapt to large environmental perturbation events.
The onset of the TOAE is relatively well understood, whereas the long-term palaeoenvironmental evolution in the aftermath and the mechanisms leading to the recovery have received less attention. Although several studies have provided local records with sedimentological and geochemical evidence for increases in continental weathering and organic carbon burial rates during the TOAE, globally integrated records are still lacking. This is hampering our holistic understanding of the respective role and efficiency of continental weathering and organic carbon burial in the carbon cycle-climate recovery. By using a multidisciplinary approach and state-of the-art mineralogical and geochemical proxies, RECOVERY is filling this knowledge gap by providing the palaeoclimatic and palaeoenvironmental evolution from the onset of the TOAE to the recovery, and by constraining the feedback mechanisms responsible for the recovery and long-term climate and carbon cycle stabilization.
RECOVERY’s specific objectives were:
(1) Providing globally integrated records of the long-term (from onset to recovery) palaeoenvironmental conditions. Four studied sites were selected: Fontaneilles (France, Subalpine Basin), Acerillo (Chile, Andean Basin), Vilyui (Russia, Siberian Basin) and Ait Athmane (Morocco, High Atlas Basin). These sites were chosen to have records from both northern and southern hemispheres and from different palaeoceanographic settings. The multiproxy approach used in this study, which combines field observations, mineralogical and geochemical analyses, allow us to detangle the influence of regional processes on global trends.
(2) Reconstructing the carbon cycle dynamics, using carbon isotope composition (13C) of marine organic matter and marine carbonates.
(3) Evaluating changes in redox conditions, nutrient level and primary productivity using trace element concentrations.
(4) Tracking the causality link between volcanic activity and environmental changes, by means of mercury and tellurium concentration in the sedimentary rocks.
(5) Tracing the response of silicate weathering to global warming, using lithium isotopes and assessing its efficiency compared to organic matter burial.
Earth’s climate history has been punctuated by several warming events that were often associated with fast increase in atmospheric greenhouse gas levels linked to the onset of large-scale volcanism. The Toarcian Oceanic Anoxic Event (TOAE, Early Jurassic) was one of the most extreme hyperthermal events in Earth history and can hence provide keys on how biogeochemical cycles have controlled Earth’s carbon cycle-climate dynamics over geological time scales. Taking the TOAE as a case study, RECOVERY aims to better understand the causes and feedback mechanisms that can enable the Earth’s system to recover and to adapt to large environmental perturbation events.
The onset of the TOAE is relatively well understood, whereas the long-term palaeoenvironmental evolution in the aftermath and the mechanisms leading to the recovery have received less attention. Although several studies have provided local records with sedimentological and geochemical evidence for increases in continental weathering and organic carbon burial rates during the TOAE, globally integrated records are still lacking. This is hampering our holistic understanding of the respective role and efficiency of continental weathering and organic carbon burial in the carbon cycle-climate recovery. By using a multidisciplinary approach and state-of the-art mineralogical and geochemical proxies, RECOVERY is filling this knowledge gap by providing the palaeoclimatic and palaeoenvironmental evolution from the onset of the TOAE to the recovery, and by constraining the feedback mechanisms responsible for the recovery and long-term climate and carbon cycle stabilization.
RECOVERY’s specific objectives were:
(1) Providing globally integrated records of the long-term (from onset to recovery) palaeoenvironmental conditions. Four studied sites were selected: Fontaneilles (France, Subalpine Basin), Acerillo (Chile, Andean Basin), Vilyui (Russia, Siberian Basin) and Ait Athmane (Morocco, High Atlas Basin). These sites were chosen to have records from both northern and southern hemispheres and from different palaeoceanographic settings. The multiproxy approach used in this study, which combines field observations, mineralogical and geochemical analyses, allow us to detangle the influence of regional processes on global trends.
(2) Reconstructing the carbon cycle dynamics, using carbon isotope composition (13C) of marine organic matter and marine carbonates.
(3) Evaluating changes in redox conditions, nutrient level and primary productivity using trace element concentrations.
(4) Tracking the causality link between volcanic activity and environmental changes, by means of mercury and tellurium concentration in the sedimentary rocks.
(5) Tracing the response of silicate weathering to global warming, using lithium isotopes and assessing its efficiency compared to organic matter burial.
Fieldwork and rock sampling was the backbone of the project. The two field campaigns initially planned (Fontaneilles and Acerillo) were successful and additional samples from Morocco (Ait Athmane) and from Russia (Vilyui) were added to further broaden our understanding of the palaeoenvironmental changes that occurred at a global scale across the TOAE.
This study (1) provides one of the most biostratigraphically well-defined high-resolution d13C records (Fontaneilles), which can serve as reference curve for the early-late Toarcian time interval; (2) documents for the first time the long-term palaeoenvironmental evolution across the TOAE and recovery phase in the southern hemisphere (Acerillo) and polar area (Vilyui); (3) supports previous observations that depositional conditions strongly modulated the development of oxygen-deficient conditions and the preservation and burial of organic matter across the TOAE. Organic matter strata (when present) are not systematically bounded to the negative CIE interval but may also be diachronous (e.g. Viluyi and Acerillo), occur stratigraphically well above in the recovery phase (e.g. at Fontaneilles) or be absent (e.g. Ait Athmane); (4) provides evidence that efficient continental weathering likely triggered long-term cooling following the TOAE warming event; (5) documents that protracted volcanic activity likely played a crucial role in the recovery.
This study (1) provides one of the most biostratigraphically well-defined high-resolution d13C records (Fontaneilles), which can serve as reference curve for the early-late Toarcian time interval; (2) documents for the first time the long-term palaeoenvironmental evolution across the TOAE and recovery phase in the southern hemisphere (Acerillo) and polar area (Vilyui); (3) supports previous observations that depositional conditions strongly modulated the development of oxygen-deficient conditions and the preservation and burial of organic matter across the TOAE. Organic matter strata (when present) are not systematically bounded to the negative CIE interval but may also be diachronous (e.g. Viluyi and Acerillo), occur stratigraphically well above in the recovery phase (e.g. at Fontaneilles) or be absent (e.g. Ait Athmane); (4) provides evidence that efficient continental weathering likely triggered long-term cooling following the TOAE warming event; (5) documents that protracted volcanic activity likely played a crucial role in the recovery.
The Laboratoire de Géologie at the University of Lyon was the ideal host institution to fruitfully achieve RECOVERY’s objectives by providing a stimulating environment and by allowing close collaboration with French and international experts. RECOVERY’s impact lies in its ground-breaking nature, which builds at the intersection of theoretical concepts and advanced analytical techniques at multiple spatial and temporal scales. The main outcomes of RECOVERY were presented at international congresses (e.g. Jurassic2023; Swiss Geoscience Meeting) and during outreach activities (e.g. Portes Ouvertes de l’Observatoire de Lyon). Dissemination and outreach activities were essential to make the most of the gained knowledge and dataset in order to valorize the project and maximize its impact.
As such, RECOVERY was a collaborative project which brought together experts from French and international research institutions to improve our understanding of Earth’s system sensitivity to changing boundary conditions. RECOVERY is also timely and relevant for the society and policy makers as it explored topics related to global warming and Earth’s resilience, fitting hence in the context of current climate change. As such, RECOVERY provides keys to better constrain the feedback mechanisms (short- and long-term silicate weathering) that can enable the Earth system to adapt to large environmental perturbation events.
As such, RECOVERY was a collaborative project which brought together experts from French and international research institutions to improve our understanding of Earth’s system sensitivity to changing boundary conditions. RECOVERY is also timely and relevant for the society and policy makers as it explored topics related to global warming and Earth’s resilience, fitting hence in the context of current climate change. As such, RECOVERY provides keys to better constrain the feedback mechanisms (short- and long-term silicate weathering) that can enable the Earth system to adapt to large environmental perturbation events.