An incident of trail rage between a hiker and biker that sent a Marin County woman to the hospital is confounding local leaders who just completed a plan for how visitors should better share 34 popular nature preserves.

A 65-year-old woman who was walking downhill in the Terra Linda/Sleepy Hollow Open Space Preserve outside San Rafael was either struck or nearly struck by a man riding uphill Thursday afternoon, according to Marin County Parks officials.

The two exchanged words, but it didn’t end there. The cyclist continued on the Luiz Ranch Fire Road near the 680 Trail and the woman followed, seeking to take a photo of the man with her cell phone, before a physical confrontation ensued, authorities said.

The woman suffered bruises on her arms, legs and head, officials said, before park staff escorted her to an ambulance. She was taken to a hospital and treated, then released. The cyclist left the area, according to authorities.

Linda Dahl, director of Marin County Parks, said she could provide only limited details of what happened because the situation remains under investigation. But she said the conflict was prompted by a disagreement over “yielding the trail.”

The parks agency recently completed a master plan that seeks to regulate its 200 miles of unpaved roads and trails. The department’s 16,000 acres of preserves are popular with a range of sometimes competing visitors, from mountain bikers to equestrians to bird watchers, and thousands of comments poured in as the plan took shape over 16 public meetings.

“This recent incident was isolated and unfortunate,” Dahl said. “It did not conform to anything we agreed to.”

Investigators have spoken with the woman involved in the confrontation as well as another person who was riding with the bicyclist, Dahl said. No arrests have been made.

Kurtis Alexander is a San Francisco Chronicle staff writer. E-mail: kalexander@sfchronicle.com Twitter: @kurtisalexander