Coastal response to late-stage

transgression and sea-level

highstand in Brazil

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

Angulo et al., 2006, Quaternary Science Reviews

Approach: Transgressive Records Preserved by SL Fall

Hein et al., 2014,

GSA Bulletin

• 5.8 ka BP; 2 - 4 m

• Gradual, mildly oscillating

SL fall

Approach: Transgressive Records Preserved by SL Fall

Caravelas Strandplain,

Bahia, Brazil

Pinheira Strandplain,

Santa Catarina, Brazil

Roy et al., 1994,

Cambr. U. Press

Study Site: Navegantes Strandplain, Santa Catarina

Rio

Grande do

Sul

Santa

Catarina

Paraná

Florianopolis

Navegantes

Tijucas

Study Site:Navegantes Strandplain

Itajaí River

• High relief (900 m)

• Relatively narrow coastal

plain (10–45 km)

• Rugged Precambrian –

Cambrian bedrock headlands

• Coast smoothed: strandplains

formed between headlands

Navegantes

Strandplain

Itajaí

Bedrock

Headland

Bedrock

HeadlandPhoto: I. Buynevich

Hein et al., 2014,

GSA Bulletin

Examples of Diverse Highstand Deposits at Navegantes

Exposed Bedrock Coast

Hein et al., 2014, GSA Bulletin

• Full exposure

• No transgressive / HS

features

• Waves crashing along

bedrock cliff at HS

Examples of Diverse Highstand Deposits at Navegantes

Transgressive Barrier Bar

Hein et

al., 2014,

GSA

Bulletin

• Shore-parallel bar; no lagoonal deposits

• Pinned to resistant upland material (bedrock)

Examples of Diverse Highstand Deposits at Navegantes

Barrier Island System

Hein et

al., 2014,

GSA

Bulletin

• Barrier w/ lagoonal deposits in protected

area of plain

• Overtops low resistance upland deposits

Hein et al., 2014,

GSA Bulletin

Modern Elevation 5.22.8

Pleistocene

Upland

Pleistocene

Upland

Lowland

(paleo-lagoon?)

Ridge Gap

(paleo-inlet?)

A Comparison Barrier Island System: Tijucas Strandplain

FitzGerald et al., in prep

N

Classification of Highstand Deposits

Hein et al., 2014, GSA Bulletin

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

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)

• Barriers stabilized: SLR

decel. to <1.5–2.0 mm/yr (5–

6 ka)Hein et al., 2014, GSA Bulletin

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.