USGS begins digital geologic mapping project

Two year project will detail 13 quadrangles in the northern foothills of the Brooks Range

Tom Hall

PNA Contributing Writer

Digital mapping has come to the North Slope... well, at least as far as the northern flank of the Brooks Range, anyway. Gil Mull, a senior petroleum geologist with the state’s Division of Geological and Geophysical Surveys, told PNA in December that the U.S. Geological Survey has begun digitizing geologic map data for a series of quadrangles (please see graphic) covering the northern foothills of the Brooks Range.

Funded primarily by the USGS, the estimated $200,000 project should take about 2 years to complete. Mull said that the ultimate goal of the project is to produce an updated, modern geologic map of the entire North Slope.

USGS geologist and project director Dave Houseknecht told PNA, “We think it will be an extremely useful project and also believe a lot of folks will benefit from it.”

Commenting on the seemingly low cost of the project, Houseknecht added, “What makes this project inexpensive is Gil’s (Mull) 35-plus years mapping. There’s no question that he is one of the few active geologists who have mapped, from one side of the state to the other, the Brooks Range foothills for 50 to 60 miles north of the range.”

Besides Mull, the state is contributing the services of DGGS geologist Ellen Harris.

“They (USGS) are providing most of the funding and the computer personnel and map editors with expertise in electronic map compilation,” said Mull. “Ellen Harris and I will be the main people from DGGS working on the revisions and compilation of new data.”

Non-government entities have also helped. Mull said that an industry consortium consisting of ARCO, Anadarko, BP, Phillips, the Arctic Slope Regional Corp. and the North Slope Borough has, for several years, contributed funding in support of mapping projects that will be used in some of the revisions.

From hodgepodge will come uniformity

Houseknecht said that not since the sixties has there been any geologic mapping of the Brooks Range foothills.

Fortunately, Mull has unpublished maps from the fifties and early sixties that he has used as the basis for his mapping.

“The older maps that I have are unpublished, but they were all done by the same group, using the same general formation names, showing the same style of portrayal of structural features,” said Mull. And even though the maps are old, they immediately drew Houseknecht’s attention when he first came to Alaska about five years ago. From the first time he saw them, “I thought how important it was to get these maps into digital form,” he said.

The conversion, though, will entail much more than digitizing the information.

“We are going to update them with modern geologic names and with a more standardized style of data portrayal,” said Mull. “We are also going to incorporate the older published data, but make things more uniform where we can.”

What’s special and who gains?

Akin to a topographical map, various colors underlying the topo portion will indicate individual rock units. Use of the color scheme will enable geologists to quickly identify similar rock formations in disparate locations.

In view of the recent interest in the NPRA, the oil industry (which had not, in the past, put out a lot effort in the outcrop area) will probably most benefit from the new digital maps, said Houseknecht.

“It’s the geology of the surface that we’re interested in here and it’s those maps that the (petroleum) companies do not have in digital form.

If you go into the foothills of the Brooks Range, the rocks that you walk on are the same rocks that are buried several thousand to as much as 10,000 feet on the North Slope,” said Houseknecht. “These surface rocks can give clues as to what lies underneath.”

Federal and state agencies involved with minerals and resource management will certainly use the new maps Houseknecht added. The two state agencies most likely to make extensive use of the maps are the DGGS (of course) and the state Division of Oil and Gas.

“I showed the first draft of a map to Ken Boyd and he’s very excited,” Houseknecht said.

Native Corporations are another primary group expected to use the new maps. Houseknecht said that the Arctic Slope Regional Corp. has already entered into an agreement with Anadarko for the foothills acreage. “One of the main attractions of the Chandler Lake quad is that we found a large exhumed oil accumulation (rocks exposed at the surface that are heavily oil stained),” he said. “It’s a very strong indicator.”

Even the mining industry should find the digital maps to be of great interest, particularly the extreme southern portions of the quadrangles.

What is and what will be

“We are beginning with these maps because they are adjacent to the NPR-A, where there is a lot of current interest,” he said.

Houseknecht said that when all 13 quads are digitized, both the USGS and DGGS will make the maps available over the Internet in one of two graphic formats. If someone wants just the image, they can simply download it (e.g., in JPEG format).

“For sophisticated users who want to have complete control of the image — say to superimpose some of their own information on the map — they will be able to get it in a GIF format called ArcInfo,” Houseknecht added.

Customers will also be able to order hard copies (roughly 42 by 60 inches) for about $20 per quadrangle.

Finally, the completed digital map will become part of a larger regional map, albeit at a smaller scale of 1:1,000,000 (1 inch = 16 miles). The addition will fill a large hole in the digital map of the state that Ric Wilson (of the Anchorage USGS office) is compiling.

For detailed information, call Dave Houseknecht at the U.S. Geological Survey, 703 648-6466, or e-mail him at [email protected]; or Gil Mull at the Alaska Geological Survey, 907 451-5031, or e-mail him at [email protected].