Increased biomass and carbon burial 2 billion years ago triggered mountain building

John Parnell,Connor Brolly

doi:10.1038/s43247-021-00313-5

Abstract

The geological record following the c. 2.3 billion years old Great Oxidation Event includes evidence for anomalously high burial of organic carbon and the emergence of widespread mountain building. Both carbon burial and orogeny occurred globally over the period 2.1 to 1.8 billion years ago. Prolific cyanobacteria were preserved as peak black shale sedimentation and abundant graphite. In numerous orogens, the exceptionally carbonaceous sediments were strongly deformed by thrusting, folding, and shearing. Here an assessment of the timing of Palaeoproterozoic carbon burial and peak deformation/metamorphism in 20 orogens shows that orogeny consistently occurred less than 200 million years after sedimentation, in a time frame comparable to that of orogens through the Phanerozoic. This implies that the high carbon burial played a critical role in reducing frictional strength and lubricating compressive deformation, which allowed crustal thickening to build Palaeoproterozoic mountain belts. Further, this episode left a legacy of weakening and deformation in 2 billion year-old crust which has supported subsequent orogenies up to the building of the Himalayas today. The link between Palaeoproterozoic biomass and long-term deformation of the Earth’s crust demonstrates the integral relationship between biosphere and lithosphere.

Highlights

The geological record following the c. 2.3 billion years old Great Oxidation Event includes evidence for anomalously high burial of organic carbon and the emergence of widespread mountain building
Several lines of evidence mark the Palaeoproterozoic as the time when mountain building commenced in the forms which have continued to the present day
The Palaeoproterozoic saw a marked increase in the biomass in the oceans, and consequent burial of organic carbon in the crust, which are recorded in the geochemical anomalies of the Lomagundi-Jatuli and Shunga events[7,8,9]

Summary

Introduction

The geological record following the c. 2.3 billion years old Great Oxidation Event includes evidence for anomalously high burial of organic carbon and the emergence of widespread mountain building. An analysis of the time interval between the burial of organic carbon and orogeny indicates that the developments of high biomass and plate tectonics are linked. Direct evidence for the deformation potential of highly carbonaceous rocks in orogens is found in an examination of major detachment surfaces in the younger Phanerozoic record.

Results

Conclusion