"My 2018 work repositions the main terrace location only 100m from my 2017 location. Given the area of Te Tarata [White Terraces] is some 13 acres, a relocation of 100m is practically insignificant."
He said his findings were a result of three years of research "tightening survey positions and hardening up landmarks" from the diary of 19th century geologist Dr Ferdinand von Hochstetter, as well as numerous field studies.
He said it was not until now, after this research had been done, that a final location of the terraces could be determined.
"Frankly the only way to assure my or anyone else's research is to drill down over Te Tarata and return a silica sample which matches the chemical profile of retention samples.
"I have taken pains to stress my survey work can only fix the terrace locations. It cannot provide evidence of terrace survival or demise. Only a physical sample can put the issue beyond doubt."
Bunn said he had previously argued against drilling the area, and if it were to be the next step, it would require archaeological, conservation and iwi protocols be satisfied.
"This process may take years. I'm aware of an iwi sentiment to leave the terrace sites undisturbed and naturally welcome whatever decision the iwi reach with respect to future research over the three terrace sites and that of Black Terrace Crater."
Bunn said he had briefed Tuhourangi Tribal Authority trustees on his latest findings six days before he made the announcement, and had later discussed with Skipwith plans to publish his findings as an independent researcher.
Skipwith said if the terraces, thought to be lost forever after the 1886 Mt Tarawera eruption, still existed, they would be on sacred ancestral land belonging to the iwi.
But he said any announcement regarding possible locations for the terraces would be made once further scientific investigation had been completed in the coming months.
"My apologies go out to our iwi as this announcement was not expected or approved and I want to assure the iwi that the TTA is solely focused on attempting to prove the location of the terraces and that any conclusions and subsequent plans would be a matter for a hui-a-iwi.
"The terraces are of great cultural significance to Tuhourangi and the opportunity to rediscover them is also of great interest to New Zealanders, and to a worldwide audience.
"However, there have been numerous attempts and similar statements made in the past as to possible locations for the terraces with assurances that those conclusions have withstood scientific scrutiny and peer review.
"Unfortunately, none of those investigations have proven fruitful and this has highlighted the need to be very confident we are searching in the right locations when conducting ongoing field investigations - extensive fieldwork in 2017 taught us that.
"Consequently, an independent review of the reverse engineering, survey principles, and data used to locate the terraces, and the placement of Hochstetter's map on today's landscape, has been requested by TAA."
Skipwith said the Tuhourangi Tribal Authority was being advised by a number of highly qualified and experienced researchers, scientists and geologists, and Niwa, as part of this team of experts, was tasked with completing those checks.
He said Niwa also proposed to undertake further non-invasive work that would enable researchers to tighten the search area.
"We are all indebted to Dr Sascha Nolden and Mr Rex Bunn for their research and scientific paper published in 2016 that set us on this path to potentially prove the location of the terraces.
"But, we are in no position to conclusively state where they could be and any announcement to the contrary would be misleading to iwi members and the general public.
"Our focus at this stage is on trying to pinpoint an exact location, nothing more."
Skipwith said Tuhourangi acknowledged the discovery of Ferdinand von Hochstetter's field journal by Dr Nolden and the tribute he had accorded Tuhourangi in gifting the iwi a copy.
"There was also some great work done by Dr Cornel De Ronde of GNS back in 2014 that he respectfully shared with the iwi and it would seem prudent as part of our due diligence, that we reach out to them as well.
"As stated earlier, we are in no position to confirm the locations of the terraces and we are continuing to conduct a rigorous scientific study of the area in the hope they can be located."
Bunn said while carrying out his research he had always worked with iwi in "friendly and constructive co-operation" and anticipated "no alteration of that relationship".
