09:50 〜 10:05
[MGI28-04] High-resolution seismic depth profiles of seafloor sediments in the southwestern Shatsky Rise: New insights for the IODP3 proposal
Shatsky Rise, a large igneous province in the northwestern Pacific, formed between 147 and 124 million years ago and is overlain by a sedimentary succession spanning nearly 150 million years, from the latest Jurassic to the Cenozoic, preserving crucial records of past oceanic environments.Various drilling expeditions (e.g., DSDP/ODP Legs 6, 32, 86, and 198) have been conducted on the rise to study paleoclimatology and paleoceanography. However, these expeditions have primarily targeted carbonate-bearing sediments, leading to a lack of records from chert and pelagic clay deposits. On the other hand, existing seismic profiles taken from the southwestern flank of Shatsky Rise by previous cruises lack the resolution needed to reveal shallow sediment structures in detail, hindering detailed stratigraphic interpretations of the sediment succession.
To fill this gap, we have proposed a new scientific ocean drilling expedition focusing on these under-explored sediments to provide a more comprehensive understanding of long-term oceanic environmental changes. To acquire site survey data for supporting the drilling science, we conducted a high-resolution multichannel seismic (MCS) survey in April 2024 (KH-24-1 cruise). The goal was to generate high-resolution seismic depth images of the sedimentary layers and the shallowest part of the igneous rocks from the southwestern flank of Tamu Massif (Southern High) of Shatsky Rise to the southwestern abyssal plain, where the oldest part of the rise was formed on the Jurassic oceanic crust. To process the acquired MCS dataset, we implemented a workflow that included basic denoising and spike noise removal, followed by deghosting and stacking velocity analysis. The time-domain RMS velocity model was then converted to the depth domain using a Dix operator, and pre-stack depth migration (PSDM) was performed to enhance imaging accuracy and structural resolution.
The compiled seismic depth images closely align with core data from Site 1213, drilled during the ODP Leg 198, confirming a sedimentary succession composed of a 400 m-thick Berriasian-Campanian chert/porcellanite sequence, which includes a distinct Early Aptian black shale layer, overlain by a 50 m-thick Pliocene-Pleistocene calcareous ooze resting on the volcanic basement. This presentation showcases the seismic depth profiles of the southwestern Shatsky Rise and explore new insights into drilling science and sedimentology. These data provide essential information for our drilling proposal, including variations in layer thickness and lithological distribution, ultimately improving our understanding of long-term environmental changes in the Pacific Ocean.
To fill this gap, we have proposed a new scientific ocean drilling expedition focusing on these under-explored sediments to provide a more comprehensive understanding of long-term oceanic environmental changes. To acquire site survey data for supporting the drilling science, we conducted a high-resolution multichannel seismic (MCS) survey in April 2024 (KH-24-1 cruise). The goal was to generate high-resolution seismic depth images of the sedimentary layers and the shallowest part of the igneous rocks from the southwestern flank of Tamu Massif (Southern High) of Shatsky Rise to the southwestern abyssal plain, where the oldest part of the rise was formed on the Jurassic oceanic crust. To process the acquired MCS dataset, we implemented a workflow that included basic denoising and spike noise removal, followed by deghosting and stacking velocity analysis. The time-domain RMS velocity model was then converted to the depth domain using a Dix operator, and pre-stack depth migration (PSDM) was performed to enhance imaging accuracy and structural resolution.
The compiled seismic depth images closely align with core data from Site 1213, drilled during the ODP Leg 198, confirming a sedimentary succession composed of a 400 m-thick Berriasian-Campanian chert/porcellanite sequence, which includes a distinct Early Aptian black shale layer, overlain by a 50 m-thick Pliocene-Pleistocene calcareous ooze resting on the volcanic basement. This presentation showcases the seismic depth profiles of the southwestern Shatsky Rise and explore new insights into drilling science and sedimentology. These data provide essential information for our drilling proposal, including variations in layer thickness and lithological distribution, ultimately improving our understanding of long-term environmental changes in the Pacific Ocean.