KNOXVILLE (AP) — A University of Tennessee professor has resigned amid an investigation into allegations of inappropriate conduct.

The Knoxville News Sentinel cited the personnel file of geography professor Henri Grissino-Mayer in reporting that he submitted his resignation Aug. 31, less than a month after the university began receiving "a series of reports about inappropriate conduct" including an intimate relationship with a student.

Grissino-Mayer did not respond to multiple requests seeking comment. He has taught at the school for more than 30 years and is director of the school's Laboratory of Tree Ring Science.

University of Tennessee spokeswoman Tyra Haag said Grissino-Mayer will receive regular pay through his last day on Oct. 1 and any accrued retirement benefits. She said the university can't comment further due to the ongoing investigation.

David Manderscheid, provost and senior vice chancellor, wrote in a Sept. 25 letter to several faculty members that he decided to accept Grissino-Mayer's resignation on Sept. 7 instead of firing him.

"Because Dr. Grissino-Mayer's conduct has been so egregious, many of us have struggled with whether the university should accept his resignation. After careful review of the competing concerns, I concluded that the most compelling interests are those of his current and former students," Manderscheid wrote.

If termination proceedings were held, students would be deposed or cross-examined, he wrote.

"In summary, I decided that I cannot in good conscience refuse to accept Dr. Grissino-Mayer's resignation even though it might be satisfying to terminate him formally for adequate cause," Manderscheid wrote.

Grissino-Mayer was placed on administrative leave with pay Aug. 8, pending the outcome of an Office of Equity and Diversity investigation, according to his file.

In his resignation letter, Grissino-Mayer said stepping down was a difficult decision.

"Many factors went into this decision — it was not made lightly, nor was it made without carefully consulting with my wife and family here in Knoxville, and especially my parents and family," he wrote in part.

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Information from: Knoxville News Sentinel, http://www.knoxnews.com