Holocene sea-level and climatic variability along the African Red Sea coast: Impacts on an ancient Egyptian civilization and implications for future coastal response to climate change Christopher Hein1 Duncan FitzGerald1; Glenn Milne2; Kathryn Bard1; Rodolfo Fattovich3 1 – Boston University, Boston, MA 2 – University of Ottawa, Ottawa, ON Canada 3 – University of Naples, “l’ Orientale”
Study Area: Mersa / Wadi Gawasis, Red Sea, Egypt
Cairo
Wadi Gawasis Qina Bend Luxor
Background: Archaeological Excavations Ceremonial Structures
N 100 m
Cliffs
Working Harbor
Background: Archaeological Excavations
Archaeological Excavations: The Harbor of Saww Prior to 5 ka: • Land routes to Punt / Bia-Punt • Nile River & across land Expeditions to southern Red Sea 5 - 3 ka: • Nubian Kingdom (Kerma) trade routs cut off • Sea route via Mersa Gawasis
Mersa Gawasis
UPPER EGYPT 1st Cataract
NUBIA Kerma
PUNT
6th Cataract
Min of the Desert
Evidence for a Harbor: Stratigraphy Auger / PulseAuger Cores: 21 transects 83 cores 3 - 6 m deep
4.6 m
msl
N 100 m
Wash Borings: 4 cores 7 - 16 m deep
Evidence for a Harbor: Stratigraphy Buried Coral Terrace:
4.6 m
msl
Coral
Modern Analog:
Evidence for a Harbor: Stratigraphy Lagoon: Medium Sand (Wadi / windblown)
4
4.6 m
msl
Very fine silty sand (lagoonal)
2
Frequency (%)
6
0 -2
2
6
10
Grain Size (Phi) WG-T6A5 (560 cm)
WG-T5A4 (550 cm)
WG-T6A6 (510 cm)
WG-T6A7 (320 cm)
• Thickness: 6+ m • Sediment: silty fine to med sand
WG-T6A6 (440 cm)
• Often capped by shell-rich shoreface sediment
Evidence for a Harbor: Stratigraphy Marine Benthic Foraminifera: Species
Substrate / Salinity Depth Temp °C Lifestyle (psu) (m)
epifaunal/ free; sand; 30-70 vegetation infaunal/ Ammonia tepida free, muddy >0 sand epifunal, Peneroplis clinging: planatus plants and 35-53 Peneroplis hard pertusus substrates Elphidium craticulatum
Quinqueloculina sp.
epifuanal, free or clinging
50
Temperate - warm
Malacology: Bivalvia: 24 sp.; Gastropoda: 9 sp.
Other
-
T15
warm brackish and 0-50 temperate hypersaline - tropical lagoons
0-70
32-65
-
18 - 27
lagoons, innermost shelf
Cold warm
hypersaline lagoons, marine marsh and shelf
T9
N
Trends (T15 T9): Elphidium craticulatum
Peneroplis pertusus
Quinqueloculina sp.
• Abundance inc. • Diversity inc. • % Gastropoda inc. • Shells hardier, thicker
Evidence for a Harbor: Stratigraphy Tidal Flat: T19A2 Wadi sand Mottled oxidized sand & clay with rootlets
4.6 m
msl
Oxidized clays 5 cm
• Location: within 1 m above MSL
• Thickness: 0.5 – 1 m
• Sediment: mud, very fine sand; many oxidized muddy layers; rootlets
Evidence for a Harbor: Stratigraphy Wadi Sands: T11A1 • Location: ubiquitous
• Sediment: gravel, sand, silt; multiple fining-upward sequences (event markers)
4.6 m
msl
• Thickness: 2.5 - >4
Fining upward sequence
m; thicker along western and southern margins of paleo-bay
10 cm
Harbor Closure: Reduction in Bay Area •
13C
dating: 21 shallow lagoon samples (mollusks)
• Archaeological evidence near occupation sites • Estimated bay areas
Harbor Closure: Bay Infilling
T11A2 T11A4
T11A7
T11A1
T11A3 T11A5
T19A1 T19A2
Wadi Floods
T19A3 T19A4
Wadi Floods
Harbor Closure: Bay Infilling
Harbor Closure: Bay Infilling
Notes: • African Humid Period: ~5 ka • TR: 0.5 m • SL >> 0?
Mid-Holocene Highstand
1.1 m Ave. terrace / wave notch height (17 loc): 1.3 m above modern MSL N
HT
Mid-Holocene Highstand
Conclusions: Sea Level vs. Sediment Supply
7 ka
5 - 4 ka
1 ka
Acknowledgements Wadi Gawasis Co-Directors: Kathryn Bard, Boston University Rodolfo Fattovich, University of Naples, “l’Orientale” Funding: • Site Benefactor: Wallace Sellers (dec.) • Geological Society of America El Baz Student Desert Research Scholarship • NOSAMS (free dates!) Stefano Tilia, Surveyor, University Suor Orsola di Benincasa, Naples, Italy Alfredo Carannante, Malacologist, University Suor Orsola di Benincasa, Naples, Italy Greer Dolby, UCLA, USA Mary Ellison, University of New Orleans, USA Farouk El Baz, Boston University, USA
Geology: Vol. 39, No. 7 (July 2011) p. 687 – 690 (hein@bu.edu)
Harbor Formation: Mid-Holocene Highstand Equatorial Syphoning I: Forebulge Collapse Mitrovica & Peltier, 1991 JGR
Equatorial Syphoning II: Hydro-isostatic Loading Mitrovica & Milne, 2002, QSR
Mid-Holocene Highstand Terraces
• Upper wadi: several erosional terraced surfaces
Modern Wadi Surface
• Lowest terrace: ~8 m above modern MSL N
Study Site
*
N
• OIS 5e (120 ka) (U/Th-dating [Hoang and Taviani, 1991; Reyss et al., 1993; Arvidson, et al., 1994]) terraces along proximal
Red Sea coast – local SL @ last interglacial within a few m of established global values • Insignificant tectonics during Holocene
Evidence for a Harbor: Harbor Entrance
• X-Sect. Area: 1300 m2 N 200 m
• Paleo-Bay Max. Area: 560,000 m2