Evidences for Paleo-Gas Hydrate Occurrence: What We Can Infer for the Miocene of the Northern Apennines (Italy)

Argentino, Claudio; Conti, Stefano; Fioroni, Chiara; Fontana, Daniela

doi:10.3390/geosciences9030134

Cited by 20 publications

(15 citation statements)

References 76 publications

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“…A drop in sea level associated with ice sheet growth would reduce overlying pressure in relatively shallow seas and may have destabilised gas hydrates globally. Gas hydrates were found to have likely 440 destabilised during the sea-level lowering of the Miocene in the present-day Appenines in Italy (Argentino et al, 2019) and in the Black Sea Basin (Kitchka et al, 2016). A release of gas hydrates, if it reached the atmosphere rather than oxidising to CO2 in overlying waters, would cause a drop in δ 13 CO2 that would also be reflected in δ 13 C (ocean) data.…”

Section: Climate Forcing and Co2 Levelsmentioning

confidence: 99%

Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model

Crichton¹,

Ridgwell²,

Lunt³

et al. 2020

Preprint

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Abstract. Since the middle Miocene, 15 Ma (million years ago), the Earth’s climate has undergone a long-term cooling trend, characterised by a reduction in sea surface temperatures by over 6 °C, with 4 to 6 °C cooling occurring in the deep ocean. The causes of this cooling are primarily thought to be linked to changes in ocean circulation due to tectonic plate movements affecting ocean seaways, together with and a drop in atmospheric greenhouse gas forcing (and attendant ice-sheet growth and feedback). In this study we assess the potential to constrain, using marine sediment proxy data, the evolving patterns of global ocean circulation and cooling of surface climate over the last 15 million years (Ma) in an Earth system model. We do this by compiling surface and benthic ocean temperature and benthic carbon-13 data in a series of seven time-slices spaced at approximately 2.5 million year intervals. We pair this with a corresponding series of seven tectonic and surface climate boundary condition reconstructions in the cGENIE (muffin release) Earth system model. In the cGENIE model, we adjust atmospheric CO2 together with the magnitude of North Pacific to North Atlantic salinity flux adjustment in a series of 2D parameter ensembles in order to match global temperature and benthic δ13C patterns in the model to the data. We identify that a relatively high CO2 equivalent forcing of 1120 ppm is required at 15 Ma in cGENIE to reproduce proxy temperature estimates in the model, noting that this CO2 forcing is dependent on cGENIEs climate sensitivity (which is as the present day) and that it incorporates the effects of all greenhouse gases. The required CO2 forcing progressively reduces throughout the subsequent six time slices delineating the observed long-term cooling trend. In order to match the evolving patterns of the proxy data, we require fundamental change in the mode of ocean circulation at 12.5 Ma with present-day-like benthic δ13C trends established by 10 Ma. We also find a general increasing strength of Atlantic overturning despite a reduction in salinity of the surface North Atlantic over the cooling period, attributable to falling intensity of the hydrological cycle and polar cooling caused by CO2-driven global cooling.

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Section: Climate Forcing and Co2 Levelsmentioning

confidence: 99%

Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model

Crichton¹,

Ridgwell²,

Lunt³

et al. 2020

Preprint

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“…The presence of gas hydrates was an additional controlling factor for seepage distribution on the paleo-wedge of the Apennine and other mountain chains [23,57]. The modelling of the paleo-gas hydrate stability recently reported by [33] for the examined outcrops, indicated that pure methane hydrates were stable at a water depth of 1000 m, within the uppermost few tens of meters to 400 m of sediment (assuming Miocene bottom water temperatures from 4 • C to 10 • C). The growth and the uplift of the thrust-related anticlines created favorable conditions for gas hydrate destabilization reducing the hydrostatic pressure and bringing gas hydrates out of their stability zone (e.g., [58]).…”

mentioning

confidence: 78%

“…Outcrop distribution highlights a causal relationship between tectonics and seepage occurrence. Recent studies also showed that some seep deposits could have originated during sea-level low-stands [29][30][31] and from gas hydrate destabilization events [32,33].…”

Section: Introductionmentioning

confidence: 99%

Miocene Seep-Carbonates of the Northern Apennines (Emilia to Umbria, Italy): An Overview

et al. 2021

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The natural emission of methane-rich fluids from the seafloor, known as cold seepage, is a widespread process at modern continental margins. The studies on present-day cold seepages provide high-resolution datasets regarding the fluid plumbing system, biogeochemical processes in the sediment, seafloor seepage distribution and ecosystems. However, the long-term (hundreds of thousands to millions of years) evolution of cold seepage remains elusive. The identification and study of outcrop analogous now exposed on land represent a valuable method for better understanding the effects of geological processes and climate forcing on the development of cold seepage systems. Here, we provide an overview on Miocene seep-carbonate deposits of the northern Apennines (from Emilia to the Umbria-Marchean sector, Italy), based on decades of field research integrated with detailed sedimentological and geochemical investigations. We report a total of 13 seep-carbonate outcrops, which formed in three different structural settings of the paleo-accretionary wedge corresponding to wedge-top basins, outer slope and intrabasinal highs at the deformational front. We discuss the recurring lithostratigraphic occurrence of seep deposits and the main compositional features (carbonate facies, carbon and oxygen stable isotopes) in order to interpret the seepage dynamics, duration and infer the contribution of methane-rich fluids released by paleo-gas hydrates. The datasets presented in this study represent a valuable complete record of cold seepage spanning ~12 Myr, that can be used to better understand factors controlling the regional-scale spatial and temporal evolution of cold seepage systems at modern active continental margins.

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“…Additional evidences can be yielded by geochemical signatures, the large dimensions of seep-carbonate deposits (several hundred meters in lateral extent and tens of meters in thickness) and the association with sedimentary instability (soft-sediment deformations) in hosting sediments [53]. Reference [54] could be considered pioneer in this background. In fact, they combined multiple field and geochemical indicators for paleo-gas hydrate occurrence based on present-day analogues to investigate fossil seeps located in the northern Apennines.…”

Section: Mediterranean Regionmentioning

confidence: 99%

“…So, References [50,54] suggest that the Mediterranean region should be investigated in order to understand the reason of the past-presence and the quite-absence of gas hydrate by using a multidisciplinary approach spanning from field data to modeling.…”

Section: Mediterranean Regionmentioning

confidence: 99%

Gas Hydrate: Environmental and Climate Impacts

et al. 2019

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This Special Issue reports research spanning from the analysis of indirect data, modelling, laboratory and geological data confirming the intrinsic multidisciplinarity of the gas hydrate studies. The study areas are (1) Arctic, (2) Brazil, (3) Chile and (4) the Mediterranean region. The results furnished an important tessera of the knowledge about the relationship of a gas hydrate system with other complex natural phenomena such as climate change, slope stability and earthquakes, and human activities.

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Evidences for Paleo-Gas Hydrate Occurrence: What We Can Infer for the Miocene of the Northern Apennines (Italy)

Cited by 20 publications

References 76 publications

Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model

Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model

Miocene Seep-Carbonates of the Northern Apennines (Emilia to Umbria, Italy): An Overview

Gas Hydrate: Environmental and Climate Impacts

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