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Inactive Faults Awatere 25+ million years of landscape evolution within New Zealandʼs Marlborough Fault System Duvall, A.R.1, Upton, P.2, Collett, C.1, Harbert, S.1, Williams, S.1, Tucker, G.3, Flowers, R.M.3 Stone, J.1, and LaHusen, S.1 1Earth and Space Sciences, University of Washington, 2GNS Science, New Zealand, 3Geological Sciences, University of Colorado 1 Low-Temperature Thermochronology 3 Detrital 10Be Cosmogenic Nuclides The Marlborough Fault System (MFS) 350 * Order of magnitude variation Hangingwall Footwall Synthesis of Landscape Patterns Pre-Earthquake Denudation Rates Awatere F. apatite helium (AHe) apatite helium (AHe) South Island, New Zealand 300 in pre-earthquake denudation AM zircon helium (ZHe) zircon helium (ZHe) 5 Wairau F. apatite fission track (AFT) apatite fission track (AFT) • Drainage anomalies indicative of river capture and rear- rate across SKR cathcments 4 250 rangement abundant in west (predominantly) & east MFS, 3 I K R 200 with fewer S. of Hope (youngest landscape) * Rates correlate well with 2 Clarence F. morphology (slope, relief, Unreset 1 150 • Overlapping river & fault orientations suggest structural Denudation Rate (mm/yr) 0 channel steepness, elevation) Conway Charwell Cribb Kowhai Hapuku S K R 2.6 S K R control to drainage network. Why do rivers align preferential- mm/yr 100 3.6 Cooling Date (Ma) Age of Deposition ly with inactive faults rather than active faults in the west? mm/yr * Rates are higher than appar- 1.26 Hapuku 50 mm/yr ent exhumation rates from Hope F. • Zones of high ksn overlap with youngest thermochron ages, Kowhai Reset 0.50 low-temperature thermochro- inset figure: Simon Lamb 0 likely regions of highest uplift rates mm/yr SKR_Amuri SKR_Fyffe SKR_Main IKR_Elliot IKR_Main Cribb Sample Location 0.99 Kaikōura nology exhumation rates SKR IKR mm/yr Charwell 10 uplift north FIGURE 7 - Be derived pre-earth- Inland Kaikoura Range Elevation Transects SW->NE 0 of Awatere Conway quake denudation rates. Early Miocene uplift footwall FIGURE 3 - Plot of thermochronology cooling dates along each elevation transect site. Gray Seaward Kaikoura Range 2 regional burial Awatere shaded region covers the range in depositional age of sampled rocks. Note that all AHe dates MFS Landscape through Time Denudation Rate are reset, whereas only ZHe in hangingwall rocks are reset. e 4 Amuri Range (Hope F.) (a). early Miocene What about after g r Pacific e n v a Ocean the earthquake? 6 regional uplift i SKR + IKR footwalls R R Depth (km) Two Stage History: longitudinal R s river valley IK e a r r n 8 uplift of i s u • 3 of the 5 catchments (in red) uplift of IKR • Miocene exhumation limited to hanging walls indicates early thrust fault- e North of Awatere F. icl n a Pliocene localised uplift and y n e ant i e t ncli t o exhumation SKR a GMC deposited ing and uplift, first in the Inland then in the Seaward Kaikōura Range k n 10 w show post-earthquake dilution in u i Awatere F. footwall A 120 100 80 60 40 20 0 o a Time (Ma) • Exhumation is rapid and widespread across the Marlborough Fault M K 10Be concentration e System after Pliocene onset of dextral faulting r d FIGURE 2 - Cooling paths from QTQt thermal e n ? t a models of low-temperature thermochron dates. Upton et al. (in prep) Collett et al. (2019) a l w n I Today folding and uplift above blind fault A • Conway, Kowhai, Hapuku experi- N ence ~ factor of 2 dilution, which is Lamb & Bibby (1989)sum (b). mid Miocene e longitudinal e s g delayed after 2017 event river valley r Planform River Patterns Planform Fault Patterns r n Pacific n i e 2 longitudinal R e a t v K s a Ocean river valley I t i R y e S a FIGURE 1 - Shaded relief map of the northeastern end of the South Island, New Zealand. (a) Upper left lin KR R nc n s w a e nticlin u r y li n a e nc A Inset (figure from Simon Lamb preventionweb.net) shows the New Zealand plate boundary. (b) Lower o u r • Kowhai headed back to pre-2017 o . M e ticlin F an e k v r AM d right Inset shows the changing plate boundary convergence vector through the 25 million years of AM e i r e e out-of-the-syncline i v r e R a g conditions? i r a e w n 10 R t thrust e e Kaikoura Orogeny from Lamb and Bibby (1989). Note that it has become more oblque toward the present t K a a FIGURE 8 - Be concentration pre and post earthquake 1 a c w a e R Stage 1: Thrusting and and Thrusting 1: Stage n A d w S time. n e a e Pacific A r r I K R Development Range/Valley a r I K R l a g Does dilution relate to coseismic e . ? l n u t r Ocean Kekerengu F. In i o a e F C s k w iv e i i A c thrust faulting, folding, and uplift R a landslide volume? R n K Charwell Cribb 1 Saxton River re N Undiluted Catchments 2 la ce 2 Alma River C (c). late Miocene / re s 1 n e in e KR at a r 3 Acheron River I longitudinal Pliocene t 3 la w n s e A 0.8 How has the landscape evolved in this C S K R S K R y lin river valley S u Charwell Cribb Hapuku s K n c nticline R o * * a y e water Diluted Catchments nclin M gap Example preliminary post-M7.8 earthquake land- Conway Be Pre] Hapuku 0.6 nticlin slide mapping (slide areas in red). 10 Pacific a e complex, long-lived tectonically active setting? out-of-the-syncline e Kowhai river ‘elbow’ R g 10 Ocean A • Be dilution correlates well with total landslide thrust an R 0.4 tributary ? volume despite differences between catchments ra . u F Be Post]/[ major river ko in terms of erosion rate, pre-eq sediment concen- e ? i 10 p a [ 0.2 o active fault K H R rd tration, and catchment hypsometry. Reults sug- watergap thrusting,uplift & C a uplift landslide volume threshold? HH HH inactive fault aw Pacific gest that landslide volume is the dominant Se 0 N right-lateral strike-slip faulting N Ocean control on diluation and the possibility of a 0 2 4 6 8 10 12 14 16 18 When did the mountains rise, when did the barbed tributary N 6 3 x 10 1 landslide volume threshold for dilution. Total Landslide Volume (m ) obtuse tributary (d). Modern re ns 20 km 20 km IKR longitudinal te i e 10 river valley a ta g FIGURE 9 - Plot of catchment Be dilution and SKR w n n Williams et al. (in prep) faults form? A ou a landslide volume. M R FIGURE 4 - (above) Planform river patterns and mapped drainage anomalies. River FIGURE 5 - (above) Map of active and inactive faults from GNS database. Inactive and r a e r elbow = channel bends ~90; obtuse trib. = trib meets river at 90 or greater; barbed trib. = iv u active category. (below) Polar histograms of Fault orientations. Anaylsis from ArcGIS. Uplift Regional R o offset k obtuse w/ deflection; water gap = river flows across divide. (below) Polar histograms of e i Plot from CircStat [Berens, 2009]. Figs. from Duvall et al. [2020] c streams a future n K River orientations (Strahler orders >1). Anaylsis from network segment routines [c/o e d r n water a R a e inactive faults active faults l A nl g gap? Stage 2: Strike-Slip and Strike-Slip 2: Stage Philippe Steer] and Topotoolbox [Schwangart and Scherler, 2014]. Plots from CircStat I n Faults Orientations C facets a 2 How have the rivers evolved at this changing R [Berens, 2009]. Figs. from Duvall et al. [2020] ra Acknowledgements and Works Cited North of Hope Fault - west North of Hope Fault - east South of Hope Fault ou ? river ? ik r incision a e e? This work was supported by National Science Foundation grants EAR-132859 and 1321735 to ? K i v g plate boundary? high-order rivers inactive faults active faults 90 90 90 C R rd r an River Orientations 120 60 120 60 120 60 a e r aw r re Pacific Duvall, Tucker, and Flowers and GSA and Evolving Earth Grants to Williams. Upton was supported 0.15 0.2 0.2 Se t u tu North of Hope Fault - west North of Hope Fault - east South of Hope Fault right-lateral N f u fu Ocean by NZ Ministry for Business Innovation and Employment (C05X1103). 150 0.1 30 150 0.15 30 150 0.15 30 0.1 0.1 strike-slip & widespread uplift 90 90 90 0.05 0.05 Berens, P., 2009. CircStat: a MATLAB toolbox for circular statistics. J Stat Sofw, 31(10), 1-21. 120 60 120 60 120 0.05 0.15 180 0 180 0 180 0 0.15 0.1 FIGURE 6 -Schematic cartoon of Marlborough Fault System landscape evolution through Collett, C.M., Duvall, A.R., Flowers, R.M., Tucker, G.E. and Upton, P., 2019: The Timing and Style of Oblique Deformation Within New Zealand's 3 150 0.1 30 150 0.1 30 150 30 90 90 90 Kaikōura Ranges and Marlborough Fault System Based on Low‐Temperature Thermochronology, Tectonics, 38, 1250-1272.
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