Ge 112. Geomorphology and Stratigraphy

Ge 112. Geomorphology and Stratigraphy HOLOCENE SEA-LEVEL CHANGE Sonja Spasojević

OUTLINE • Motivation • Sea-level change: processes and time-scales • Methodology for defining relative sea-level (RSL) • Holocene RSL around the globe • Barbados, Tahiti, Papua New Guinea • Scotland • Caribbean and South America • 5. Conclusions

MOTIVATION Sea-level height (m) Age (million years BP) • My research interest • Modeling long-term geodynamic influence on sea-level change • How does long-term sea-level change?

MOTIVATION • This presentation: • How does sea-level changes during Holocene at different locations? • What are the controlling processes for Holocene sea-level change? Ge112 class notes

SEA-LEVEL CHANGE: Processes and time-scales • At any location relative sea-level (RSL) change is a result of: • Eustatic change • Isostatic or tectonic change • Local coastal processes

SEA-LEVEL CHANGE: Processes and time-scales • Eustatic level (sea-surface) change • Change in water volume • Glacial eustasy-ocean and ice volume in balance • Water expansion/contraction (change of temperature and salinity) • Change in hydrologic cycle, storage in sediments, etc. • Isostatic or tectonic change • Local coastal processes

SEA-LEVEL CHANGE: Processes and time-scales • Eustatic level (sea-surface) change • Change in water volume • Glacial eustasy-ocean and ice volume in balance • Water expansion/contraction (change of temperature and salinity) • Change in hydrologic cycle, storage in sediments, etc. • Change in ocean basin volume • Tectono-eustasy • Change of spreading rate- very slow • Isostatic or tectonic change • Local coastal processes

SEA-LEVEL CHANGE: Processes and time-scales • Eustatic level (sea-surface) change • Change in water volume • Glacial eustasy-ocean and ice volume in balance • Water expansion/contraction (change of temperature and salinity) • Change in hydrologic cycle, storage in sediments, etc. • Change in ocean basin volume • Tectono-eustasy • Change of spreading rate- very slow • Change of water distribution • Geoidal isostasy • Isostatic or tectonic change • Local coastal processes

SEA-LEVEL CHANGE: Processes and time-scales • Eustatic level (sea-surface) change • Isostatic or tectonic change • Glacial isostasy • Uplift beneath the melted ice • Subsidence on the rim of melted ice • Local coastal processes

SEA-LEVEL CHANGE: Processes and time-scales • Sea-surface level change (eustatic level) • Isostatic or tectonic change • Glacial isostasy • Uplift beneath the melted ice • Subsidence on the rim of melted ice • Hydro isostasy • Melted water creates additional load on the ocean floor- subsidence • Local coastal processes

SEA-LEVEL CHANGE: Processes and time-scales • Sea-surface level change (eustatic level) • Isostatic or tectonic change • Local coastal processes • Local isostatic adjustment • Tectonic compression • Elastic rebound • Faulting, folding, tilting • Earthquakes • Tidal regime change • …etc.

Methodology for defining RSL curves • Sea-level indicators • Corals • Acropora palmata is widely used, lives within 5 m of the water surface • Microatolls- indicative range ~3cm • 2) Geomorphologic features (wide indicative range) • Paleoshoreline notches • Paleoreef flats • Beach deposits • Terraces • 3) Fixed biologic indicators • Rock clinging oyster beds • Fossil tubework encrustations • 4) Fossils and microfossils • 5) Sedimentary facies Mostly based on Woodroffe (2005)

Methodology for defining RSL curves • Use a variety of environmental indicators to define RSL • Terminology: • Indicative meaning • Reference water level (RWL) • Indicative range (IR) Woodroffe (2005)

HOLOCENE RSL around the globe Papua New Guinea Barbados Tahiti

Tahiti: Barrier reef drilling • 2 reef cores (700 m apart): P6, P7 • Sequence of reef carbonates • overlie basalts at 114 m depth • 2 units, unconformity at ~87 m depth • 230Th/234U dating: error 30-60 years • Species assemblage: corals, • encrusting algae, foraminifers, • gastropods • Far from plate boundaries Bard et al. (1996)

Tahiti RSL curve • Continuous increase in RSL • Small change @ 11,500-11,000 yr. BP • Hiatus @ 13,700 years • Major sea-level jump Bard et al. (1996)

Barbados offshore drilling program • 16 cores • Near-continuous sequence • 7,800-17,100 yr BP • Radiocarbon dating (error <130 yr) • Active subduction zone, located on • accretionary prism between two • plates • assumed continuous uplift Fairbanks (1989)

Barbados RSL curve • Best estimate for Holocene sea-level change ~120 m • 13,500: MWP-1A– meltwater pulse 1Amajor SL rise • 11,000: MWP-1B- metlwater pulse 1B another SL rise • 11,500-11,000: Younger Dryas thermohaline circulation stopped as a result of major fresh water input in North Atlantic •  New Guinea curve very similar to Barbados curve, supports MWP 1A and 1B events Bard et al. (1996)

Barbados, Tahiti, Papua New Guinea: Eustasy • Rise in sea-level from 18,000-3,000 yr • Contemporaneous meltwater pulses and Younger Dryas event • Although tectonic setting very different, RSL curves very similar •  This largely defines eustatic signal Bard et al. (1996)

HOLOCENE RSL around the globe: Scotland Shennan et al. (2000)

HOLOCENE RSL around the globe: Scotland Shennan et al. (2000) Peltier et al. (2002)

HOLOCENE RLS around the globe: Scotland Shennan et al. (2000)

HOLOCENE RSL around the globe: Scotland • RSL determined using: • Cores • Lithostratigraphy • Biostratigraphy • Polen • Diatoms • Chronostratigraphy organic limus silt and clay org.dep. sand Shennan et al. (1999, 2000)

HOLOCENE RSL around the globe: Scotland Sea-level fall Age (ka) Shennan et al. (2000)

Scotland: Glacial isostasy 1) Glacial period ICE 2) Ice melts SCOTLAND 3) Rebound Uplift Subsidence Subsidence Last glacial maximum

HOLOCENE RLS around the globe Caribbean and South America Milne et al. (2005)

Caribbean and South America • 24 samples • Mangrove peats, others? • 55 samples • Sedge, mangrove, swamp forest ? • 4 samples • Corals, mangrove sediments, massive carbonates • 8 samples • Vermitid Age (ka) Jamaica Suriname Recife Curacao Sea-level (m) Milne et al. (2005)

Caribbean and South America • 28 samples • Mangrove, vermitid • 8 samples • Peat, shells • 27 samples • Vermitids, shells, wood • 27 samples • Shells in raised beaches Rio de Janeiro Strait of Magellan Recife Beagle Channel Santa Catarina Sea-level (m) Age (ka) Milne et al. (2005)

Caribbean and South America • Can not be attributed completely to eustatic signal Eustatic signal Model • Very different behavior RSL records for • a coast of a single continent • Caribbean coast tectonically active • Atlantic coast- passive margin Milne et al. (2005)

Jamaica: geoidal isostasy Glacial geoid Interlacial geoid Age (ka) Jamaica SL (m) Time (ka) 0 2 6 8 4 10 Geoidal isostasy Sea-level (m) Non-eustatic Eustatic signal Data Milne et al. (2005)

Jamaica: Non-eustatic Geoidal isostasy Non-eustatic Eustatic signal Data Hydro isostasy Non-eustatic Glacial isostasy Milne et al. (2005)

Jamaica: Glacial isostasy 1) Glacial period ICE 2) Ice melts Geoidal isostasy Non-eustatic: spatially varying 3) Rebound Uplift Eustatic signal Subsidence Subsidence Data Hydro isostasy Non-eustatic Glacial isostasy Milne et al. (2005)

Jamaica: Hydro isostasy Glaciation Geoidal isostasy M1 Deglaciation Non-eustatic: spatially varying M2 > M1 Eustatic signal Sea-floor subsidence Data Hydro isostasy Non-eustatic Glacial isostasy Milne et al. (2005)

CONCLUSIONS • Large number of factors influence RSL • Different stratigraphic and geomorphologic data used • Areas far from ice-sheets (Barbados, Tahiti, Papua New Guinea) • Constrain eustatic sea-level change • Climatologic, oceanographic studies • Glaciated regions (Scotland) • Affected by postglacial rebound • Constrain rheological structure of the Earth • Intermediate regions • Complex interplay of ice-, ocean- and tectonic- related processes • Geodynamic implications

REFERENCES • Bard, E., Hamelin, B., Arnold, M., Montaggioni, E, Cabioch, G., Faure, G., and F. Rougerie, 1996, Deglacial sea-level record from Tahiti corals and the timing of global meltwater discharge, Nature, 382, 241-244. • Chappell, J. and H.Polach, 1991, Post-glacial sea-level rise from a coral record at Huon Peninsula, Papua New Guinea, Nature, 349, 147-149. • Clark, J.A., Farrell, W.E., and W.R. Peltier, 1978, Global changes in postglacial sea level: A numerical calculation, Quaternary research, 9, 265-187. • R.G. Fairbanks, 1989, A 17,000-year glacio-eustatic sea level record: influence of glacial melting on the Younger Dryas event and deep-ocean circulation, Nature, 342, 637-642. • Milne, G.A., Long, A.J., and S.E. Bassett, 2005, Modeling Holocene relative sea-level observations from the Caribbean and South America, Quaternary Science Reviews, 24, 1183-1202. • Peltier, W.R., Shennan, I., Drummond, R. and B. Horton, 2002, On the postglacial isostatic adjustment of the British Isles and the shallow viscoelastic structure of the Earth, Geophysical Journal International, 148, 443-475. • Scholl, D.W., Craighead, F.C., and M. Stuiver, 1969, Florida submergence curves revised: Its relations to coastal sedimentations, Science, 163, 562-564. • Shennan, I., Tooley, M., Green, F., Innes, J., Kennington, K., Lloyd, J. and M. Rutherford, 1999, Sea level, climate change and coastal evolution in Morar, northwest Scotland, Geologie en Mijnbouw, 77, 247-262. • Shennan, I., Lambeck. K., Horton, B., Innes, J., Lloyd, J., McArthur, j., Purcell, T., and M. Rutherford, 2000, Late Devonsian and Holocene records of relative sea-level changes in northwest Scotland and their implications for glacio-hydro-isostatic modeling, Quaternary Science Reviews, 19, 1103-1135. • Shennan, I., Peltier, W.R., Drummond, R. and B. Horton, 2002, Global to local scale parameters determining relative sea-level changes and the post-glacial isostatic adjustment of Great Britain, Quaternary Science Reviews, 21, 397-408. • Toscano, M.A. and J. Lundberg, 1998, Early Holocene sea-level record from submerged fossil reefs on the southeast Florida margin, Geology, v.26, n0.2, 255-258. • Woodroffe, S.A. and B.P. Horton, 2005, Holocene sea-level changes in the Indo-Pacific, Journal of Asian Earth Sciences, 25, 29-43.

Non-eustatic signal TOTAL Glacial isostasy Hydro isostasy Milne et al. (2005)

HOLOCENE RSL around the globe 1) Glacial period Collapsing forebulge submergence ICE 2) Ice melts 3) Rebound Uplift Age (ka) Subsidence Subsidence Jamaica SL (m) Clark et al. (1978)

Ge 112. Geomorphology and Stratigraphy