GEOLOGICAL STRUCTURE OF WAIRARAPA VALLEY, NEW-ZEALAND, FROM SEISMIC-REFLECTION PROFILING

Three Mini-Sosie seismic reflection profiles across part of southern Wairarapa, North Island, with a combined length of 22 km roughly normal to the main structural trend, reveal shallow crustal structure down to a depth of 1.5 km in upper Cenozoic strata hidden below upper Quaternary gravel deposits. Profiles across the Wairarapa Plain, intersecting Highway 2 at a point 3.5 km southwest of Masterton reveal the following structures south-eastward from the Alfredton Fault at the north-western edge of the Wairarapa Plain. 1. Chester Anticline formed in upper Miocene-basal Pliocene strata, buried under the north-west flank of the Taratahi Syncline (see below). 2. Taratahi Syncline, 7 km wide, its north-west flank unconformably overlying Chester Anticline, its bottom flat and nearly level for 5 km, and its south-eastern flank rising in a concentric curve to the adjacent Peter Cooper Anticline. 3. Peter Cooper Anticline and on its south-east side the complementary Fern Hill Syncline, both concentric folds, and strongly developed in Upper Miocene and Pliocene strata, but weakly developed in Quaternary strata. -from Authors