Rising Tide organiser Alexa Stuart handed herself into police in Sydney on Wednesday afternoon after stopping a coal train at Sandgate earlier in the day.
Ms Stuart travelled to the office of Federal Environment Minister Tanya Plibersek with a bag of coal that was taken from the train.
Police took Ms Stuart's details and recorded her statement of guilt.
Nine people have been charged in relation to the protest on the rail line.
Police arrested four men - aged 24, 48, 60 and 69 - and five women - aged 18, 20, 23, 42 and 66.
They were taken to Newcastle Police Station and all charged with cause obstruction to railway locomotive or rolling stock, enter enclosed non-agricultural lands with a serious safety risk, and enter enclosed land not prescribed premises without a lawful excuse.
All nine were refused bail to appear before Newcastle Local Court on September 26.
More than community members rallied at Labor MPs electoral offices across the country on Wednesday following the government's approval of three coal mining projects, including two in the Hunter, on Tuesday.
"I stopped a coal train this morning in Newcastle and now I am here at Tanya Plibersek's office to turn myself in. I am here to show Tanya what taking responsibility for your actions looks like because she and her government have abdicated their responsibility to young people, to fossil fuel workers deserving a fully-funded transition, and to all Australians," Ms Stuart, a former Newcastle young citizen of the year and volunteer primary ethics teacher said.
"It is an absolute disgrace that instead of funding a transition for workers, the government is continuing to approve new coal and gas projects when we are in a climate crisis. They are breaking their promise of delivering real climate action, and they are condemning my generation to a future of climate disasters and instability."
"I will accept the consequences of my actions."
Earlier, climate protesters were removed from a coal train at Sandgate after a two-hour stand-off with police.
Officers - including rescue specialists - swarmed the scene near the Sandgate rail bridge just after 10am on Wednesday after reports activists had brought a train to a sudden stop and climbed aboard.
Nine protesters were seen on top of the carriage, shovelling coal out, waving signs and chanting their objections to new coal projects.
All nine people from the group Rising Tide appeared to refuse police requests to get down themselves, and refused offers from rescue officers to climb down.
They were fitted with harnesses and lowered on ropes.
The Newcastle Herald understands multiple people were arrested and put into police vehicles, at least one had been taken to Newcastle Police Station by about 12pm, the first to be removed.
No charges had been laid by Wednesday evening.
Highway patrol police, specialist officers, the rescue squad and uniformed officers converged near the railway corridor as the operation unfolded.
More than a dozen staff from Aurizon and the Australian Rail Track Corporation (ARTC) were also called to attend the incident.
The unauthorised protest was prompted by the federal government signing off on two major Hunter coal mine extension projects on Tuesday, saying they were needed and would support hundreds of jobs across the region.
The protesters on board the coal train hung a large banner which read: "Albo: if you don't stop new coal, we will!"
They waved signs which said "coal until 2066 is madness", "stop burning our future" and "new coal = climate failure".
More than a dozen other Rising Tide representatives and the Knitting Nannas showed their support from outside the rail corridor, chanting "coal, don't dig it, leave it in the ground, start to get with it".
Rising Tide is planning a Newcastle Harbour blockade in November for climate action, which they claim will bring 10,000 people to the city.
Earlier this year, separate climate group Blockade Australia controversially blocked Hunter rail lines across two weeks of sustained disruption.
