AN ABSTRACT OF THE THESIS OF Russell J. Van Dissen for the degree of Master of Science in Geology presented on February 15, 1989. Title: Late Quaternary Faulting in the Kaikoura Region, Southeastern Marlborough, New Zealand Redacted for privacy Abstract approved: Dr. Robert 8.0eats Active faults in the Kaikoura region include the Hope, Kekerengu, and Fidget Faults, and the newly discovered Jordan Thrust, Fyffe, and Kowhai Faults. Ages of faulted alluvial terraces along the Hope Fault and the Jordan Thrust were estimated using radiocarbon-calibrated weathering-rind measurements on graywacke clasts. Within the study area, the Hope Fault is divided, from west to east, into the Kahutara, Mt. Fyffe, and Seaward segments. The Kahutara segment has a relatively constant Holocene right-lateral slip rate of 20-32 mm/yr, and an earthquake recurrence interval of 86 to 600 yrs: based on single-event displacements of 3 to 12 m. The western portion of the Mt. Fyffe segment has a minimum Holocene lateral slip rate of 16 + 5 mm/yr .(southeast side up); the eastern portion has horizontal and vertical slip rates of 4.8+ 2.7 mm/yr and 1.7 + 0.2 mm/yr, respectively (northwest side up). There is no dated evidence for late Quaternary movementon the Seaward segment, and its topographic expression is much more subdued than that of the two western segments. The Jordan Thrust extends northeast from the Hope Fault, west of the Seaward segment. The thrust has horizontal and vertical slip rates of 2.2 + 1.3 mm/yr and 2.1 + 0.5 mm/yr, respectively (northwest side up), and a maximum recurrence interval of 1200 yrs: based on 3 events within the last 3.5 ka. Drainage-divide elevation and mountain-front morphology of the Seaward Kaikoura Range, abundant evidence for recent activity on the Jordan Thrust, and lack of activity on the Seaward segment indicate that the late Quaternary displacement on the Hope Fault is transferred northward, west of the Seaward segment. The low slip rates for the thrust, compared to the higher lateral slip rates along the Kahutara and Mt. Fyffe segments, suggest that displacement on the Jordan Thrust does not accommodate all the displacement transferred from the Hope Fault. The remaining displacement is accommodated by distributed shear within the Torlesse rocks behind the thrust, and folds in front of and behind the thrust, although the latter was not documented for the Holocene. Late Quaternary Faulting in the Kaikoura Region, Southeastern Marlborough, New Zealand by Russell J. Van Dissen A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Completed February 15, 1989 Commencement June 1989 APPROVED: Redacted for privacy Professor of Geology/in charge of major Redacted for privacy n of depat-tment of Geology Redacted for privacy Dean of Gradua0School (7 Date thesis is presented February 15, 1989 Typed by researcher for Russell J. Van Dissen ACKNOWLEDGMENTS For logistical assistance in the office and in the field, I am indebted to the New Zealand Geological Survey, especially the Earth Deformation Section. R.I. Walcott, Victoria University of Wellington, aided in the arrangements necessary in getting me to New Zealand. For help with various phases of field work I thank S. Beanland, K.R. Berryman, L.J. Brown, G.H. Browne, H.N.C. Cutten, D.L. Fellows, M.G. Laird, J. Pedersen, R. Williams, and P.R. Wood. Aerial photography of the field area was provided for by the New Zealand Geological Survey; I thank D.L. Fellows, D.L. Homer, and P.R. Wood for their help. J. van Berkel provided the use of the University of Canterbury field station at Kaikoura. I would also like to acknowledge the farmers and residents of the Kaikoura area, the Marlborough Catchment Board, especially D.A. Mackay, and the New Zealand Forest Service in Kaikoura, without their help and cooperation this project would have been much more difficult and much less enjoyable. I thank S. Beanland and R.S. Yeats for their discussions about and critical reviews of this manuscript. With deep gratitude I thank the New Zealand-United States Educational Foundation whose award of a Fulbright Study Grant to me made funding for this project possible. TABLE OF CONTENTS INTRODUCTION 1 Location and Previous Work 5 Methods and Quaternary Geology 6 DESCRIPTION OF THE ACTIVE FAULTS IN THE KAIKOURA REGION 13 Hope Fault 13 Kahutara Segment 13 Mt. Fyffe Segment 20 Seaward Segment 28 Jordan Thrust 29 Kekerengu Fault 40 Fidget Fault 41 Fyffe Fault 42 Kowhai Fault 46 DISCUSSION 48 Slip Rate on Hope Fault 48 Comparison of Slip Rate on Hope Fault with Pacific-Indian Plate Motion 55 Earthquake Recurrence Interval 56 Transfer of Displacement on Jordan Thrust 57 CONCLUSIONS 67 REFERENCES CITED 69 LIST OF FIGURES Figure Page 1. Active faults in the Kaikoura region 2 2. Marlborough faults and offshore deformation 3 3. Calibration curve for modal weathering-rind thickness of surface Torlesse rocks 9 4. Faulted alluvial terraces at Sawyers Creek, Kahutara segment of the Hope Fault 17 5. Weathering-rind data from Sawyers Creek 18 6. Faulted alluvial fan at Mt. Fyffe Gate, Mt. Fyffe segment of the Hope Fault 21 7. Faulted and warped alluvial terraces at Waimangarara River, Mt. Fyffe segment of the Hope Fault 23 8. Profiles P-P of deformed alluvial terraces, 1 Waimangarara River 24 9. Faulted alluvial terraces at Hapuku River, Mt. Fyffe segment of the Hope Fault 26 10. Profile of Seaward Kaikoura Range drainage divide 31 11. Faulted alluvial terraces at Clinton River, Jordan Thrust 32 12. Profiles Pi-P of faulted alluvial terraces, Clinton 33 13. Weathering-rind data from Clinton River 34 14. Jordan Thrust exposure in Happy Valley. 38 15. Fyffe Fault exposure at Big Hau 43 16. Fyffe Fault where it makes a 35° turn in strike north of Big Hau 45 17. Faulted alluvial terraces at Charwell River, Kahutara segment of the Hope Fault 49 LIST OF FIGURES - continued Figure Page 18. Latest Pleistocene slip-rate for the Hope Fault 54 19. Idealized relation between Hope Fault, Jordan Thrust, and Puhi Puhi syncline 60 20. Schematic cross-section across the Inland and Seaward Kaikoura Ranges 62 21. Elevation of Seaward and Inland Kaikoura Ranges projected parallel to direction of tectonic transport 65 LIST OF TABLES Table Page 1. Late Quaternary displacements and ages for faulted terraces in the Kaikoura region 14 2. Late Quaternary lateral and vertical slip- rates for the active faults in the Kaikoura region 15 3. Late Quaternary lateral slip-rates for the Hope and Kakapo Faults near Glynn Wye 52 4. Average recurrence interval of earthquakes on the Kahutara segment with varying single- event displacement and varying slip-rate 58 LATE QUATERNARY FAULTING IN THE KAIKOURA REGION, SOUTHEASTERN MARLBOROUGH, NEW ZEALAND INTRODUCTION The present-day tectonic setting of New Zealand is dominated by the diffuse transform boundary between the Indian and Pacific plates, a transform that links the east- facing Tonga-Kermadec Trench and the west-facing Puysegur Trench and Macquarie Ridge (McKenzie and Morgan 1969). The major element of this transform is the right-lateral strike-slip Alpine Fault. The Alpine Fault includes a restraining bend (inset of Fig. 1, and Fig. 2). Yeats and Berryman (1987) point out that there isa tendency to straighten out a restraining bend by shifting the plate boundary onto new faults that are on trend with the boundary on the opposite side of the bend. The plate motion east of the bend is taken up by the Marlborough fault system (inset of Fig. 1, and Fig. 2) which is made up of the Wairau, Awatere, Clarence, and Hope Faults. In the Marlborough region, the convergence rate of the Pacific plate with respect to the Indian plate is 47 mm/yr at an azimuth of 264 ± 2° (Walcott 1979). The Wairau Fault, formerly the most important of the Marlborough faults, shows all the separation of Paleozoic and Mesozoic tectonostratigraphic terranes between Nelson and south Westland (inset of Fig. 1). It thus predates the 2 Active thrust fault showing 173'451 dip direction. Teeth toward I upthrown side. .# k" 70 Active strike-slip fault showing GS 3\ir GR. dip direction.u, upthrown fid9e side. 70 Ae Middle MII M Possible active fault showing dip direction. Late Quaternary (905 m) displacement not documented. Te 00 i 4 Whekere 4 Drainage divide of Seaward (2596 ml # Kaikoura Range. &M(tm) Al exander , 0 kau.,...,./ 28 cy, (2610 rn)Ar. ee J *km `t .0 48 4.-C> N Sounders .,* 4e15' 5 Half Moon Soy mt. CA (215,1-79r .iir/40 illokAt 68 11... / 85 t ngNite. 1 / F It. 7 / 0,000men e i 0:` 11 se9 Mt. Fiffe AC, 6 4)(1602) /90# liluku 47 eSIA River CI\ Vt. col"to 000m tudy Area 044) ':41* APqe N 0°1 . Oavhoi Chorwell 17330.E Riker River Location Mop Figure 1. Map of active faults in the Kaikoura region. Localities and features discussed in the textare Big Hau (BH), Charwell River (CW), Clinton River (CR),Floodgate Creek (FC), George Saddle (GR), George Stream (GS), Goidmine Creek (GM), Happy Valley (HV), Hapuku River (HR), Jordan Stream (JS), Kowhai Saddle (KS), Luke Creek (LC), Mt. Fyffe Bends (MB), McLean Stream (MS), Puhi Puhi River (PPR), Upper Kowhai Fault (UK),Sawyers Creek (SC), Snowflake Stream (SF), and Waimangarara River (WR). Inset shows Alpine Fault, Marlborough faults (seealso Fig. 2), Southern Alps, and offset tectonostratigraphicterranes (dots). Arrow shows azimuth and rate, in mm/yr, of relative motion of the Pacific Plate with respectto the Indian Plate.