Bulletin Article

Integrated three-dimensional (3-D) paleomorphologic and sedimentary modeling was used to predict the basin architecture and depositional pattern of Pleistocene forearc basin turbidites in a gas hydrate field along the northeast Nankai Trough, off central Japan. Structural unfolding and stratigraphic decompaction of the targeted stratigraphic unit resulted in successful modeling of the paleobathymetry at the time of deposition. This paleobathymetry was characterized by a simple U-shaped paleominibasin. Subsequent turbidity current modeling on the reconstructed paleobathymetric surface demonstrated morphologically controlled turbidity current behavior and selective turbidite sand distribution within the minibasin, which strongly suggests the development of a confined turbidite system. Among three candidate inflow patterns, a northeasterly inflow pattern was determined as most likely. In this scenario, flow reflection and deflection caused ponding and a concentration of sandy turbidite accumulation in the basin center, which facilitated filling of the minibasin. Such a sedimentary character is undetected by seismic data in the studied gas hydrate reservoir formation because of hydrate-cementation–induced seismic anomalies. Our model suggests that 3-D horizon surfaces mapped from 3-D seismic data along with well-log data can be used to predict paleobasin characteristics and depositional processes in deep-water turbidite systems even if seismic profiles cannot be determined because of the presence of gas hydrates.
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Explorer Article


Three speakers from the AAPG-AAPG Foundation’s Global Distinguished Lecture Program will be on tour in November, making stops in the western parts of North America and throughout the Asia-Pacific Region.

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The options for female geologists might not have matched those of their male counterparts in the 1930s and ‘40s, but for some women – they were opportunities nonetheless – and they deserved chasing. Helen Laura Foster, an AAPG member who is now 94, took full advantage of those opportunities.

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Mystery of the deep: No one knows for sure what quantity of gas hydrates awaits discovery deep in the earth, but projections are auspicious.

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Japan has taken a leap forward in natural gas production by conducting the first successful production test of natural gas from marine hydrates. Could this be the“bridge” fuel needed in the coming energy transition?

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What would you give for an early detection system for earthquakes? Detecting those first waves of compression could help.

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Explorer Division Column EMD


Every six months, chairs of the Energy Minerals Division committees convene and report on developments in the areas they cover. In this column, we highlight important observations from these recent reports.

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Explorer Historical Highlight


The Toyokawa field is a small oil field, covering an area of about six square kilometers, located in northeastern Japan’s Akita Prefecture. The hillock area where the Toyokawa oil field is situated formerly was covered with natural asphalt (tar) deposits that had erupted from the subsurface. The current scenery resembles the famous La Brea Tar Pit in Los Angeles.

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At first glance the structural contour map and the cross section shown here look as if they had been published in the late 1920s by AAPG in the “Structure of Typical American Oil Fields” memoir.

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Explorer Regions and Sections


Frigid temperatures and blizzard conditions moved across Europe in early February, setting new records – and as temperatures fell, gas prices from the main pipeline in Russia rose to the highest levels since 2006.

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