Visitors to the information plaza at Grand Canyon National Park are told how the Colorado River carved the great chasm over millennia through the rocks of the Colorado Plateau. But nestled among the hiking guides and souvenirs sold at the plaza bookstore is a book that tells a very different story of how the canyon came to be.

A federal review of whether the book -- which asserts that the canyon was created in a matter of days as a result of the same flood that had threatened to sink Noah and his ark -- should be sold at the park has been delayed for months as officials wrestle with the issue of separation of church and state.

"Grand Canyon: A Different View," compiled by Colorado River guide Tom Vail, includes essays by creationists who maintain that the canyon's sedimentary strata were formed by deposits from Noah's flood and that the canyon's age should be based on a biblical rather than an evolutionary timeline -- making it just thousands of years old, not the 6 million years that geologists say.

Critics believe the creationist book should not be sold by a shop on government property because it contradicts the park's mission to teach science.

In January, David Shaver, the chief of the Geologic Resources Division of the National Park Service, issued a memo recommending that the book be pulled, because it "purports to be science when it is not, and its sale in the park book store directly conflicts with the Service's statutory mandate to promote the use of sound science in all its programs, including public education." Vail's book was sent to the national headquarters for a review of the appropriateness of its sale at the park. The Interior Department, which oversees the Park Service, expected a final decision in February, but it has been delayed as lawyers at the Interior and Justice departments tackle the issue, Park Service spokeswoman Elaine Sevy said.

No deadline has been set for a final ruling, and the book will continue to be sold until a decision is made, she said.

"It's difficult on where to draw the line on these issues," she said. ". . . This could be precedent-setting, and we are moving very carefully and very cautiously."

Jeff Ruch, executive director of Public Employees for Environmental Responsibility, a nonprofit advocacy group, said the Park Service "in essence made the decision to keep the book on sale."

Meanwhile, the book has been moved from the natural science section to the inspirational section in the store.

The bookstore is run by a nonprofit group, but park officials approve which books can be sold there. Several others have been rejected in past months for including outdated or inaccurate information. Members of the scientific community are questioning why Vail's book was approved.

"The science presented is substandard, inaccurate and greatly at variance with the mainstream scientific view presented at Grand Canyon National Park," said Eugenie C. Scott, executive director of the National Center for Science Education. "Nobody is saying this book should be taken out and burned," Scott said. "But it should not be sold at this bookstore."