Uplifted marine terraces and some other aspects of late quarternary geology in northern Taranaki
- Author
- Duff RO
- Year
- 1993
- Journal / Source
- MSc
- Publisher / Organisation
- University of Otago
- Pages
- 205 pp
- Keywords
- Tongaporutu, Awakino, Whitecliffs, Urenui, Mokau
- Summary
- At least four Pleistocene uplifted marine terraces occur in the north Taranaki area. These are the NT1, NT2, NT3, and an older terrace formation (informally named 'Urenui upland terrace surface'). The NT1 Terrace, correlated with ∂¹⁸O Substage 5a (c. 80ka B.P.), is restricted to the Turangi Road-Motunui coastal area. An average uplift rate of 0.29m.ka⁻¹ is inferred from the NT1 strandline altitude at Turangi Road. The NT2 Terrace, correlated with ∂¹⁸O Substage 5e (c. 120ka B.P.), is the dominant terrace in north Taranaki occurring along the entire length of the field area (Motunui- Awakino River mouth). The NT2 Terrace is the sole terrace formation north of White Cliffs and is clearly delineated by a linearly concordant abandoned sea cliff. The average uplift rate for the last 120ka was inferred from the NT2 strandline altitude at several localities: At Tongaporutu river mouth 0.27m.ka⁻¹. 10km further north at Mohakatino an uplift rate of 0.20m.ka⁻¹ was found. About 3km north at Mokau River mouth uplift rates of c. 0.15m.ka⁻¹ and 0.17m.ka⁻¹ were respectively calculated for the north and south sides. A clear trend of constant tectonic uplift rates between Motunui and Tongaporutu and linearly decreasing uplift rates north of Tongaporutu toward the Awakino River was thus found. The NT3 Terrace, correlated with ∂¹⁸O Substage 7a (c. 210ka B.P.), wedges out just north of Urenui (near Okoki Pa). The 'Urenui upland terrace surface' occurs above the NT3 Terrace in the Urenui-Onaero area and probably encompasses more than one terrace formation, but these were not differentiated. The completely dissected North Taranaki Surface (NTS) occurs inland of the marine terraces. The altitude of the envelope of ridge-crest concordance (c. 250m above MSL) is not representative of total tectonic uplift as it has been erosionally degraded by an unpredictable amount.