Magmatic Forcing of Cenozoic Climate?

Abstract

Established theories ascribe much of the observed long-term Cenozoic climate cooling to atmospheric carbon consumption by erosion and weathering of tectonically uplifted terrains, but climatic effects due to changes in magmatism and carbon degassing are also involved. At timescales comparable to those of Milankovitch cycles, late Cenozoic building/melting of continental ice sheets, erosion, and sea level changes can affect magmatism, which provides an opportunity to explore possible feedbacks between climate and volcanic changes. Existing data show that extinction of Neo-Tethyan volcanic arcs is largely synchronous with phases of atmospheric carbon reduction, suggesting waning degassing as a possible contribution to climate cooling throughout the early to middle Cenozoic. In addition, the increase in atmospheric CO 2 concentrations during the last deglaciation may be ascribed to enhanced volcanism and carbon emissions due to unloading of active magmatic provinces on continents. The deglacial rise in atmospheric CO 2 points to a mutual feedback between climate and volcanism mediated by the redistribution of surface masses and carbon emissions. This may explain the progression to higher amplitude and increasingly asymmetric cycles of late Cenozoic climate oscillations. Unifying theories relating tectonic, erosional, climatic, and magmatic changes across timescales via the carbon cycle offer an opportunity for future research into the coupling between surface and deep Earth processes. Plain Language Summary Among the most fascinating contemporary developments in theEarth Sciences is the idea that plate tectonics and climate changes are coupled through complex cycles. More than four decades of study have revealed tantalizing examples of relationships between processes near the Earth's surface and deeper within. Accounting for such a surface-deep Earth process coupling has improved our understanding of major climate and tectonic events for virtually all timescales. So far, however, the role of magmatism was overlooked. Magmatism exerts a strong influence on the amount of greenhouse gasses in the atmosphere because of volcanic outgassing. In turn, tectonic and climatic changes control the transfer of rocks, water, and ice masses at the Earth surface and within the Earth's interior, thereby affecting the production, transfer, and eruption of magmas. Unravelling the interactions between surface and deep Earth processes accounting for magmatism will help managing natural resources and mitigating natural hazards. Even more importantly, understanding how climate is naturally related to plate tectonics and magmatism will allow scientists to assess the anthropogenic perturbations to the Earth system and anticipate ongoing and future climate changes.

India-Asia collision as a driver of atmospheric CO2 in the Cenozoic

“…ooling of Earth's climate during the Cenozoic is broadly thought to have been related to decreasing atmospheric CO 2 concentrations [1][2][3] . The key factors leading to such decreases remain the subject of considerable debate [4][5][6][7][8] . Two hypotheses have been proposed.…”

“…The first invokes an increasing rate of CO 2 consumption by silicate weathering during the Cenozoic, caused by the uplift of the Tibetan Plateau [9][10][11][12] . The second focuses on a decreasing rate of CO 2 release from Earth's interior in the Cenozoic, attributed to the shutdown of the Neo-Tethyan decarbonation subduction factory during the India-Asia continent collision 7,8,13 . Despite the clear distinction between these two hypotheses, both contain the premise that the India-Asia collision is the ultimate cause of atmospheric CO 2 concentration variations in the Cenozoic.…”

“…Several studies [14][15][16][17][18] indicate that Cenozoic magmatism and metamorphism in the Tibetan Plateau are reliable recorders of the evolution of India-Asia collision processes and the formation of the Himalayan-Tibetan orogen. Magmatic and metamorphic degassing, which are fundamentally linked to such plate tectonic processes, are important parts of the Earth's deep carbon cycle on million-year time scales 8,[19][20][21] . Thus, a better understanding of magmatic and metamorphic emissions in Tibet should bring with it the potential for providing critical constraints on explanations of atmospheric CO 2 concentration variations in the Cenozoic.…”

“…Thus, a better understanding of magmatic and metamorphic emissions in Tibet should bring with it the potential for providing critical constraints on explanations of atmospheric CO 2 concentration variations in the Cenozoic. It is even possible that deep carbon cycle processes associated with the India-Asia collision might have served as critical drivers of both atmospheric CO 2 concentration variations and palaeoclimatic changes in the Cenozoic 8,20 .…”

Climatic control on the location of the Southern Andes volcanic arc

“…We expect this recognition to be broadly applicable to other volcanic arcs worldwide and particularly relevant for volcanic arc ore deposits, the exploitation of which is primarily conditioned by the regional topography itself. Because volcanic arcs provide a substantial contribution to the evolution of climate across timescales, this recognition provides an additional evidence of the tight coupling between climate and plate tectonics 46,47 .…”