Pacific monitoring

Victor Schmidt • Houston

Seabed monitoring is beginning off the west coast of Canada in a zone of high tectonic activity due to several small tectonic plates that are being subducted under the North American continent. Trans-current fault systems are also active in the region.

The idea behind the research project is to create a fiber-optic network linking dozens of seabed nodes. Each node would hold multiple sensors for long-term monitoring of the biological, chemical, and physical properties of the seabed environment.

The seabed monitoring off Vancouver Island, being conducted by the University of Victoria, will be followed by a pilot project in Monterey Bay, California. These installations are part of a larger regional observatory called Neptune that will be built by the National Science Foundation. Marine resear-chers envision a communication grid with Internet links, so that anyone with a computer could work with the data flowing from the sensor net.

Cretaceous sea level rise

Cores drilled from the New Jersey coastal plain found that ice sheets likely caused massive sea level change during the Late Cretaceous – an interval previously thought to be ice-free. Led by Kenneth G. Miller of Rutgers, The State University of New Jersey, scientists examined cores from ODP Leg 174AX, an onshore extension of an offshore leg. They found that sea level changes were large (> 25 m) and rapid during the Late Cretaceous. Seismicity, seismic stratigraphy, and sediment-distribution patterns indicate minimal tectonic effects on the New Jersey Coastal Plain during this time. Another explanation for such large, rapid changes is the waxing and waning of continental ice sheets.

"Our studies of cores in New Jersey provide one of the best dated estimates of how fast and how much sea-level changed during the greenhouse world of the Late Creta-ceous," Miller explained. "The Earth was certainly much warmer at that time, probably due to high carbon dioxide levels in the atmosphere. However, at the same time, our estimates require that ice sheets grew and decayed on Antarctica during this period of peak warmth, a previously heretical view."

The propose explanation is that the ice sheets were restricted to Antarctica, ephe-meral, and paced by Milankovitch forcing. The ice sheets would not have reached the Antarctic coast, explaining the relative warmth in Antarctica, but still could significantly alter global sea level. The study results were published in the Geological Society of America Bulletin, March/April issue.

EXPLORATION

Sea of Okhotsk

TGS-Nopec Geophysical Co., in cooperation with Dalmorneftegeophysica (DMNG), will shoot a multi-client 2D seismic survey northeast of Sakhalin Island in the Sea of Okhotsk. The project will gather 9,100 km of data to examine deeper basins immediately east of the island's producing fields and will infill the company's 1998 survey.