Tectonically-triggered sediment and carbon export to the Hadal zone.

Area of Science:

• Marine geology
• Paleoceanography
• Geochemistry

Background:

• Deep ocean trenches are critical archives of Earth's history, preserving records of seismic activity and organic carbon burial.
• Understanding sediment dynamics in hadal zones (>6 km depth) is crucial for comprehending global carbon cycles.

Purpose of the Study:

• To investigate the origin and depositional processes of organic carbon in the Japan Trench.
• To utilize radiocarbon (¹⁴C) dating of organic carbon fractions for chronological constraints.
• To explore the relationship between tectonic events and sediment supply in deep-sea environments.

Main Methods:

• High-resolution ¹⁴C analysis of bulk organic carbon and its thermal decomposition fractions.
• Ramped pyrolysis/oxidation for organic carbon characterization.
• Analysis of stable isotopes (δ¹³C) to infer carbon sources.

Main Results:

• Hemipelagic sedimentation in the Japan Trench is punctuated by episodic inputs of pre-aged organic carbon.
• ¹⁴C ages and δ¹³C values indicate that this older carbon originates from the adjacent continental margin.
• Tectonically triggered gravity flows likely supply this material, coinciding with known earthquake events.

Conclusions:

• ¹⁴C dating of organic carbon thermal fractions provides robust chronological control for deep-sea sediment sequences.
• Tectonic activity significantly influences sediment composition and carbon flux in hadal trenches.
• These findings enhance our understanding of carbon cycling and sequestration in extreme deep-sea environments.