Beu: Evolution of Janthina and Reduzia 
151 
Age 
m.yr. 
1 - 
2 - 
3- 
4- 
Tephras, 
dates 
Kawakawa 
Fordell 
Griffins Road - 
Rangitawa, 0.34- 
Onepuhi, 0.57 
Kupe, 0.63 
Kaukatea, 0.86 
Potaka, 1.05 
Rewa, 1.20 
Mangapipi, 1.51 — 
Ridge, 1.56 
Pakihikura, 1.58 
Mangahou, 1.63 1 r 
Ototoka, 1.64 
Table Flat, 1.70 
Vinegar 
Waipuru 
lat, 1.70 ->rt 
Hill, 1.75 J r 
j, 1.79 — 1 
Ohingaiti 
Kowai 
Eagle Hill 
Lithostratigraphy 
Rapanui Fm. 
Brunswick Fm. 
Landguard Sand 
Putiki Shellbed 
Castlecliff 
Section, 
MIS 11-31 
Unconformity at 
the coast; 
MIS 33-53 in 
inland sections 
Maxwell Group 
Tewkesbury Fm. 
Nukumaru Sand 
Nukumaru Lst. ▲ 
Upokonui Sand A 
Hautawa Shellbed 
Te Rama Shellbed 
Parihauhau Shellbed 
Te Rimu Sand 
Wilkies Shellbed 
Makokako Sdst. 
Paparangi Sdst. 
Waverly Fm. 
Waipipi Fm. 
Tangahoe Fm. 
Upper Waitotara 
Valley, and inland 
Whanganui, Rangitikei 
River sections 
Magneto 
-strat. 
CO 
CO 
=) 
< 
o 
1.78 
1.94 
2.14 
2.59 
3.03 
3.12 
3.21 
3.33 
3.60 
Stages 
o 
LLI 
CO 
< 
o 
CL 
< 
=> 
£ 
o 
< 
g_ 
CL 
< 
O 
CL 
O 
< 
Z 
o 
< 
tr 
CQ 
£ 
< 
o 
CO 
< 
_l 
LU 
O 
< 
N 
Z 
LU 
O 
< 
CL 
< 
LLI 
_l 
o 
z 
< 
N 
Epoch 
LLI 
Z 
LLI 
o 
o 
I- 
co 
LU 
LU 
Z 
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o 
Figure 17. Stratigraphical column of Pliocene-Pleistocene rocks in Whanganui Basin, New Zealand, showing precisely dated positions 
of Janthina fossils. Stratigraphy simplified from Carter and Naish (1998,1999), most lithological details not shown; tephras from Pillans 
etal. (2005). Symbols: A Janthina chavani; • Janthina typica. Grey tone = stratigraphical hiatus. 
Pleistocene 41-ka glacial-interglacial sea-level fluctuations 
(Naish etal., 1998; Pillans etal., 1998). Sealevel oscillated 
by c. 50 m during the earlier 41-ka cycles and by up to 130 
m during the 100-ka cycles of the last 800,000 years, so 
the sea retreated from the basin during all glacial periods. 
Consequently, almost all Mangapanian and younger glacial 
periods are represented by unconformities in this basin. 
The succession consists of many cyclically deposited thin 
formations with strongly distinct lithologies and sharp 
boundaries, deposited during interglacial periods. Opoitian- 
Waipipian rocks in inland sections, particularly those 
exposed along the Whanganui, Turakina and Rangitikei 
Rivers, were deposited in slightly deeper water and are 
less obviously cyclical. The basin is only gently deformed, 
and the succession is exposed well in many river sections 
and along the coast. It contains many dated silicic tephras 
(Alloway et ah, 1993; Pillans et al., 2005; Fig. 17) which, 
along with geomagnetic polarity stratigraphy (e.g., Seward 
et al., 1986, Kamp & Turner, 1990, Turner & Kamp, 1990, 
Turner et al., 2005; Fig. 17) and detailed analyses of 
