A transdisciplinary and community-driven database to unravel subduction zone initiation

Abstract

Subduction zones are pivotal for the recycling of Earth's outer layer into its interior. However, the conditions under which new subduction zones initiate are enigmatic. Here, we constructed a transdisciplinary database featuring detailed analysis of more than a dozen documented subduction zone initiation events from the last hundred million years. Our initial findings reveal that horizontally forced subduction zone initiation is dominant over the last 100 Ma, and that most initiation events are proximal to pre-existing subduction zones. The SZI Database is expandable to facilitate access to the most current understanding of subduction zone initiation as research progresses, providing a community platform that establishes a common language to sharpen discussion across the Earth Science community.

Fig. 1. SZI events in space and time.

Some of the SZI events that occurred in the last 120 million years are included in the SZI database version 1.0 and are indicated a in terms of the present-day geographic locations of corresponding geologic evidence on an interrupted Mollweide projection of the Earth’s bathymetry, and b in terms of their temporal occurrence, accompanied by an event-specific uncertainty estimate, oldest known volcanic arc age, and reconstructed SZI type.

Fig. 2. SZI forcing endmembers and SZI types.

The two endmembers characterising SZI indicate the dominant forcing to be either—but never exclusively—a vertical (i.e., some combination of plate buoyancy force, the force from any surface load, and vertical mantle-flow force), or b horizontal (i.e., some combination of tectonic force and horizontal mantle-flow force). All known SZI events can further be grouped into one of the three types, c Newly destructive (a subduction fault establishing from an intact-plate portion or some sort of non-subduction-related plate weakness), d Episodic subduction (a subduction fault establishing at the same location following a previous, yet terminated subduction zone with the same polarity), and e Polarity reversal (formation of a new subduction fault with opposite polarity to the fault of the pre-existing, terminating subduction zone).

Fig. 3. SZI events of the West Pacific subduction realm.

The reconstructed events based on the SZI database compilation include a the Ryukyu SZI event at around 6 Ma (modified from ref. ), b the Philippine SZI event at around 9 Ma^,, c the New Hebrides-New Britain event at around 10 Ma^,, d the Halmahera SZI event at around 16 Ma^,, e the Tonga-Kermadec SZI event at around 48 Ma, and f the Izu-Bonin-Mariana SZI event at around 52 Ma. Shown are the new subduction zones (pink lines), other active (solid purple lines) and inactive (dashed purple lines) subduction zones, spreading ridges (solid red lines) and transform faults (red dashed lines).

Fig. 4. Remaining SZI events included in the SZI database.

The reconstructed events based on the SZI database compilation include a the South-Sandwich SZI event at around 40 Ma (modified from ref. ), b the Cascadia SZI event at around 48 Ma^,, c the Lesser Antilles event at around 49 Ma^,, d the Sunda-Java SZI event at around 50 Ma, e the Aleutian SZI event at around 53 Ma, and f the two SZI events, Anatolia and Oman, at around 104 Ma^,. Shown are the new subduction zones (pink lines), other active (solid purple lines) and inactive (dashed purple lines) subduction zones, spreading ridges (solid red lines) and transform faults (red dashed lines).

Fig. 5. Quantitative SZI database analysis.

The number of SZI events that fulfil specific aspects (dark pink bars) versus the total number of SZI events diagnosed (light pink bars; indicating a total of 13 SZI events). a–c The distribution of all SZI events into the different SZI types and former plate settings, and various other distinctive tectonic and mantle dynamic properties. d Total numbers of SZI events representing a given Earth-system characteristic. ‘Nearby’: within a 1500 km radius.

Fig. 6. Cross-relations between SZI types and plate structures.

SZI events are grouped according to their SZI type and diagnosed for common structural plate features. No square indicates unknown or unclear data.