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Coastal response to late-stage transgression and sea-level highstand in Brazil Christopher Hein, Duncan FitzGerald, Joao Thadeu de Menezes, Antonio Klein, Marcio Albernaz, William Cleary Geological Society of America 21 October 2014


Approach: Transgressive Records Preserved by SL Fall

Angulo et al., 2006, Quaternary Science Reviews


• 5.8 ka BP; 2 - 4 m • Gradual, mildly oscillating SL fall

Hein et al., 2014, GSA Bulletin


Approach: Transgressive Records Preserved by SL Fall Roy et al., 1994, Cambr. U. Press

Pinheira Strandplain, Santa Catarina, Brazil

Caravelas Strandplain, Bahia, Brazil


Study Site: Navegantes Strandplain, Santa Catarina Paranรก Navegantes

Tijucas Santa Catarina Rio Grande do Sul

Florianopolis


Study Site: Navegantes Strandplain • High relief (900 m) Bedrock Headland Navegantes Strandplain

• Relatively narrow coastal plain (10–45 km) • Rugged Precambrian – Cambrian bedrock headlands • Coast smoothed: strandplains formed between headlands

Itajaí Itajaí River Bedrock Headland

Photo: I. Buynevich


Hein et al., 2014, GSA Bulletin


Examples of Diverse Highstand Deposits at Navegantes Exposed Bedrock Coast • Full exposure • No transgressive / HS features • Waves crashing along bedrock cliff at HS

Hein et al., 2014, GSA Bulletin


Examples of Diverse Highstand Deposits at Navegantes Transgressive Barrier Bar • Shore-parallel bar; no lagoonal deposits • Pinned to resistant upland material (bedrock)

Hein et al., 2014, GSA Bulletin


Examples of Diverse Highstand Deposits at Navegantes Barrier Island System • Barrier w/ lagoonal deposits in protected area of plain • Overtops low resistance upland deposits

Hein et al., 2014, GSA Bulletin


2.8

Modern Elevation

5.2

Lowland (paleo-lagoon?)

Pleistocene Upland

Pleistocene Upland

Ridge Gap (paleo-inlet?)

Hein et al., 2014, GSA Bulletin


A Comparison Barrier Island System: Tijucas Strandplain

FitzGerald et al., in prep

N


Classification of Highstand Deposits Sediment Supply: • In situ, shelf, fluvial • Oceanographic conditions • Bedrock headlands • Fronting barrier systems Upland Migration Potential (UMP): • Wave energy • Erodability of upland deposits • Upland slope Hein et al., 2014, GSA Bulletin


Deposits of the Mid-Holocene Highstand in Brazil • 28 documented highstand deposits along Brazilian coast • Elevations: 0 to > 5 m above modern MSL • Ages: ~ 4–7 ka

Hein et al., 2014, GSA Bulletin


Deposits of the Mid-Holocene Highstand in Brazil • Diversity: local geological & oceanographic controls • Lagoonal deposits extend to modern shoreline (& beyond?) • Barriers present when modern SL crossing (6.9–7.7 ka) • Rapid migration: early Holocene (SLR: 2–3 mm/yr)

Hein et al., 2014, GSA Bulletin

• Barriers stabilized: SLR decel. to <1.5–2.0 mm/yr (5– 6 ka)


Implications for Transgressive Coastal Systems Coastal response to SLR is non-linear: • Threshold SLR rate for stability (slow migration / vertical accretion) of barrier systems at mid-Holocene: 2.0 mm/yr Coastal response to SLR is non-uniform: • Site specificity associated w/ formation of HS deposit types • Diversity (3 HS deposit types) identified w/in single embayment (Navegantes)


Associated Manuscript Hein, C.J., FitzGerald, D.M., Cleary, W.J., Klein, A.H.F., de Menezes, J.T., Albernaz, M.B., 2014. Coastal response to late-stage transgression and sea-level highstand. Geological Society of America Bulletin, v. 126, no. 3/4, p. 459-480.

Brazil Highstands Talk  
Brazil Highstands Talk  

PDF of talk from the 2014 annual meeting of the Geological Society of America. Based on work published in GSA Bulletin in January 2014 (http...

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