Subaerial volcanism broke mid-Proterozoic environmental stasis

Area of Science:

• Geoscience
• Paleoclimatology
• Biogeochemistry

Background:

• The mid-Proterozoic era (1.8–0.8 billion years ago) is characterized by marine anoxia, low marine primary productivity (MPP), and limited eukaryotic biodiversity.
• This period has been viewed as environmentally stagnant, but recent findings suggest intermittent disturbances and evolutionary events.

Purpose of the Study:

• To investigate the impact of volcanic activity on terrestrial weathering and MPP during the mid-Proterozoic.
• To challenge the notion of a static Earth by examining environmental dynamics.

Main Methods:

• Analysis of 1.4-billion-year-old tropical offshore sediments.
• Precise mercury (Hg) and lithium (Li) isotopic analyses.

Main Results:

• Local volcanism introduced fresh rock substrates, enhancing chemical weathering and denudation in tropical lowlands.
• Increased nutrient influx, particularly phosphorus from volcanic derivatives, stimulated MPP rates.
• Heightened organic carbon burial was observed, linked to increased MPP.

Conclusions:

• Volcanic events acted as significant environmental disturbances during the mid-Proterozoic.
• These disturbances, driven by volcanism, likely contributed to increased MPP and organic carbon burial, potentially breaking the long-term static state of the era.