Changes in the Indonesian Throughflow Since the Late Miocene Based on Radiolarian Assemblages From ODP Site 710 in the Western Tropical Indian Ocean: Implications of the Indo‐Pacific Gateway (Indonesian Seaway)

The Indo‐Pacific Gateway is a narrow tropical passage connecting the Pacific and Indian Oceans, and alterations in its topographic configuration can significantly influence the volume of water exchanged between the two oceans through the Indonesian Throughflow (ITF). In the modern ocean, the ITF extends from the surface to a depth of 500 m, with its strongest flow occurring in the upper thermocline (100–300 m). Here, we present radiolarian assemblage data from Ocean Drilling Program Site 710 in the western tropical Indian Ocean to reconstruct the history of ITF variability since the Late Miocene. The radiolarian assemblages associated with the ITF can be categorized into two groups: (a) surface ITF taxa, linked to shallow waters, and (b) thermocline ITF taxa, which correspond to subsurface waters. A significant decrease in the relative abundance of surface ITF taxa occurred at 7.5 Ma. Additionally, a faunal turnover from high‐salinity thermocline taxa to low‐salinity thermocline ITF taxa was observed at 3.5 Ma, suggesting a paleoceanographic transition from higher to lower salinity conditions in the thermocline. We propose that these changes reflect modifications in the topographic configuration of the Indo‐Pacific Gateway, which likely occurred in a stepwise manner over these periods. Radiolarian‐based SST data indicate stepwise cooling from 9.0 to 6.5 Ma, followed by a reversal to a warming trend from 4.5 to 2.0 Ma, with a slight decrease in SST after 2.0 Ma. These SST variations are likely influenced by regional topographic changes such as ITF dynamics, in addition to global climate trends.

• Publication year

  2026

• Venue

  Paleoceanography and Paleoclimatology

• Publication date

  2026-02-01

• Fields of study

  Not labeled

• Identifiers
  DOI 10.1029/2025PA005165
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar

• No claims are published for this paper.

• No concepts are published for this paper.

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