Presentation on theme: "Professor Brent Wilson FGS Petroleum Geoscience Programme, Department of Chemical Engineering, The University of the West Indies, St. Augustine."— Presentation transcript:
Professor Brent Wilson FGS Petroleum Geoscience Programme, Department of Chemical Engineering, The University of the West Indies, St. Augustine
A few definitions Ecostratigraphy: The study of the occurrence and development of fossil communities throughout geologic time Middle to Late Quaternary: the last ~0.78 Ma – latter part of the Pleistocene and the Holocene Inner Neritic: 0 – 20 m water depth Middle Bathyal: 500 – 1000 m water depth
Impetus behind this study – a failed research question Streeter (1973), Gaby and Sen Gupta (1985): marked glacial- interglacial contrasts in benthonic foraminifera at bathyal and abyssal depths Signal varies in strength aerially (Streeter and Lavery, 1982) Some papers report muted contrasts (Sen Gupta et al., 1991; Wilson, 2008) Wilson and Costelloe (2011) - classification of abundance biozone boundaries Do AB boundaries coincide with glacial-interglacial boundaries?
An Advance Organiser (as education people call them) This talk will demonstrate: Increase in organic matter flux at ODP Site 1006 (Santaren Channel) Flux of shallow water foraminifera independent of sea level change Bathyal and neritic regime shifts across Marine Isotope Stages 8-9 Percent carrying capacity changes of common bathyal species across MIS 8-9
What are Forams? For those who weren’t taught these things at school Single celled bugs <1 mm Planktonic (float near sea surface) Benthonic (live on seafloor) Shelled Narrow ecological niches Abundant in marine environments Beautiful Bolivina jiattongae Wilson, 2006
Some neritic, coral reef forams Specimens modern, from St. John, USVI C, G, H and I symbiotic with algae – need light Restricted to shallow water Wilson, B. (2011). The impact of hurricanes on epiphytal Foraminifera on rhizomes of the seagrass Thalassia testudinum, Nevis, north-eastern Caribbean Sea. In Pirog, R. S. (ed.), Seagrass: Ecology, Uses and Threats, Nova Science Publishers, Hauppauge, New York, USA, , Figure 1.
Around St. Kitts, Asterigerina carinata dominates between 6-17 m. Around Jamaica, Sigmavirgulina tortuosa common on seagrasses at <3 m Around Nevis, Triloculina bermudezi common in polluted bays at <3 m This information will be important later on Maps from Wilson, B., Orchard, K. and Phillip, J. (2012). SHE Analysis for Biozone Identification among Foraminiferal Sediment Assemblages on Reefs and in Associated Sediment around St. Kitts, Eastern Caribbean Sea, and its Environmental Significance. Marine Micropaleontology, 82-83,
Light blue areas, shoal water Dark blue areas, bathyal to abyssal water Study area at left The carbonate Bahama Platform
When a carbonate platform sheds sediment into adjacent basin during highstands of sea level Frequent during Quaternary interglacials What is highstand shedding?
What is a drift deposit? Anselmetti F S et al. Geological Society of America Bulletin 2000;112: Wedge of sediment along continental margin reworked by margin-parallel currents Shallow drifts – surface currents Deep drifts – subsurface counter currents May rework turbidites Coarse-grained for depth of occurrence Good hydrocarbon reservoirs
Shallow drift between Bahamas and Florida Santaren Current joins with Florida Current to become Gulf Stream Source of material in drift unclear – Bahamas, Cuba or both: clays from continental crust (Cuba) much aragonite (Bahamas)
Santaren Drift on Seismic Section – Miocene to Recent (25 million years)
Changes in lithology Subunit IA ( mbsf): light grey and white to pale yellow nannofossil ooze Subunit IB (>7.28 mbsf): light grey nannofossil ooze with interbedded clays and silty clays Is there a change in fauna at the change in lithology? A typical subunit IB cycle: from Eberli, G. P., Swart, P. K. & Malone, M. J. 1997a. Site In: Proceedings of the Ocean Drilling Program, Initial Reports (eds Eberli, G. P., Swart, P. K. & Malone, M. J.), pp
Above: Marine Oxygen Isotope Stages from aragonite flux Below: Neritic foraminiferal flux (as percentage) in Cores 1-3, ODP Hole 1006A Odd numbered stages are interglacials – every ~100 ka High flux in MIS 9, but clear oxygen isotope signal – not slumping en masse to site? 37% of foraminifera in deep-water ODP 1006A derived from shoal-water <20 m deep Onwards to the (reefal) forams! 26 ka
Diversity measured using information function H = -Σp i ·lnp i, where p i = proportional abundance of ith species Note change in mean diversity at ~10.5 m Change not coincident with change in lithology Change part way through MIS 9 Change in organic carbon flux? Shallow water foram diversity in ODP Hole 1006A
Axis 1Axis 2Axis 3Axis 4Axis 5Axis 6 Eigenvalue % variance Angulogerina occidentalis0.60– – – Articulina pacifica–0.8651– – – Asterigerina carinata–0.512– – –0.2359– Brizalina paula –0.4187– –0.3565– Brizalina subexcavata0.42– – Caribeanella polystoma–0.6941– –0.1611– Cibicides advena– – Elphidium translucens– – – Miliolinella circularis–0.6195–0.2757–0.2056– – Planulina foveolata– – Quinqueloculina auberina–0.3422– – – Quinqueloculina lamarckiana–0.5023–0.2015– – Quinqueloculina poeyana–0.5896–0.1575– – Rosalina bahamaensis–0.7992– – –0.1915– Rosalina globularis0.12–0.3549– –0.3289– Sagrina pulchella0.53– – Sagrina pulchella primitiva0.30– Sigmavirgulina tortuosa0.78– – Siphonina pulchra– – Triloculina bermudezi– – Shoal-water recovery dominated by Asterigerina carinata (11%), Caribeanella polystoma (12.1%) and Rosalina bahamaensis (22%) Principal components analysis indicates these are not the best species to use for ecostratigraphy of ODP 1006A
Distribution of selected shoal-water species A above = Articulina pacifica. Most abundant in and above MIS 9 B above = Sigmavirgulina tortuosa. Almost absent in MIS 8-9 C above = Triloculina bermudezi. Confirms increased organic flux from MIS 9 onwards
What happened to the bathyal assemblages? Left: MIS vs. bathyal forams (= in situ productivity) in top 3 cores, ODP Hole 1006A Note dilute signal in MIS8-9 Right: Decrease in diversity across MIS9 (indicative of enhanced carbon flux in deeper water)
Downslope transport of bathyal foraminifera %T b – percentage of total recovery as ‘bathyal’ foraminifera Some species positively correlated with %T b (Globocassidulina subglobosa, Sigmoilopsis schlumbergeri) – largely autochthonous, 39% of ‘bathyal’ assemblage Some species negatively correlated with %T b – (Cassidulina laevigata, C. reflexa, Lenticulina rotulata) – augmented by allochthonous specimens, 19% of ‘bathyal’ assemblage
Bathyal forams as percentage of bathyal foram community Above: Cassidulina reflexa abundant in MIS 9 Below: Globocassidulina subglobosa rare in MIS 9, no correlation with other MISs
Percentage carrying capacity K p : A prospective ecostratigraphic tool Percentage point change in abundance of a species Δp i between two samples given by Δp i = p it+1 – p it Rate of population change in percentage points for each percent at time t (r t ) given by r t = Δp i /p it Linear regression of r t against p it gives r t = r m – s·p it Intercept r m = rate of increase in r t where p it approaches zero Slope s = combined strength of intraspecific, interspecific and abiotic interactions for the species investigated
Changes in K p across MIS9 for selected bathyal benthonic foraminifera K p can vary over time for a species Points of changes in K p for a species mark position of species’ regime shifts Regime shifts in different species not always synchronous Regime shift in G. subglobosa in upper section shown by multiple attractors
“There is something fascinating about science. One gets such wholesale returns of conjecture from out of a trifling investment of fact.” (Mark Twain) “We all know that we do not need a complete data set to write an acceptable (hi)story. A nice story can equally well be written on the basis of a very few data and a fair amount of imagination.” ( C. W Drooger, 1993, Radial Foraminifera; Morphometrics and Evolution, p. 19) A Warning!
What caused the event in MIS8-9? Megatsunami McMurtry et al. (2007) – raised marine deposits on Bermuda indicate mega-tsunami between MIS 9-11 Would have stripped Bahama Platform of neritic sediment Hearty and Olson (2008) – tsunami deposit of MIS 11 highstand age (399 ± 11 ka); sea levels +21 m? Waelbroek et al. (2002) – MIS 11 highstand only ~5 m above present Slumping No slumping from Bahama Platform reached Santaren Drift (Rendle-Buhring and Reijmer 2005; Mulder et al. 2012) Slumping from Cuba/Hispaniola, reworked by Santaren Current?
Conclusions 1 regarding ODP Hole 1006A Reefal source mostly <14 m (Asterigerina carinata) Neritic foraminiferal flux unrelated to glacial-interglacial cycles Change in diversity at ~10.5 m reflects increase in organic carbon flux – reflected in abundance of Triloculina bermudezi Bathyal community – mixed autochthonous and allochthnous specimens (Cassidulina reflexa, Globocassidulina subglobosa) Some percentage carrying capacities change across MIS 9 Globocassidulina subglobosa shows complex pattern of change in percentage carrying capacity above MIS 9
Conclusions 2 regarding ODP Hole 1006A So, two events in ODP 1006A. Flux of reefal foraminifera highest in MIS 8-9 Change in flux of organic carbon across MIS 8-9 Might not be related Possible tsunami in MIS 8-9? Doubtful Slumping from Cuba/Hispaniola?
References Buzas, M. A., Smith, R. K. & Beem, K. A Ecology and systematics of foraminifera in two Thalassia habitats, Jamaica, West Indies. Smithsonian Contributions to Paleobiology, 31: Bernet, K. H., Eberli, G. P. & Gilli, A Turbidite frequency and composition in the distal part of the Bahamas transect. In: Proceedings of the Ocean Drilling Program, Scientific Results (eds Swart, P. K., Eberli, G. P., Malone, M. J. & Sarg, J. F.). Eberli, G. P., Swart, P. K. & Malone, M. J. 1997a. Site In: Proceedings of the Ocean Drilling Program, Initial Reports (eds Eberli, G. P., Swart, P. K. & Malone, M. J.), pp Peltier, W. R. & Fairbanks, R. G Global glacial ice volume and Last Glacial Maximum duration from an extended Barbados sea level record. Quaternary Science Reviews, 25: Phipps, M., Jorissen, F., Pusceddu, A., Bianchelli, S. & Stigter, H. C. d Live benthic foraminiferal faunas along a bathymetrical transect ( m) on the Portuguese margin (NE Atlantic). Journal of Foraminiferal Research, 42: Rose, P. R. & Lidz, B Diagnostic Foraminiferal Assemblages of Shallow-water Modern Environments: South Florida and the Bahamas. Sedimenta, 4: Todd, R. & Low, D Foraminifera from the Bahama Bank west of Andros Island. US Geological Survey Professional Paper, 683-C: 1-22.
More references (yawn) Wilson, B The Environmental Significance of Some Microscopic Organisms Around Nevis, West Indies. West Indian Journal of Engineering, 28: Wilson, B The environmental significance of Archaias angulatus (Miliolida, Foraminifera) in sediments around Nevis, West Indies. Caribbean Journal of Science, 42: Wilson, B Guilds among epiphytal foraminifera on fibrous substrates, Nevis, West Indies. Marine Micropaleontology, 63: Wilson, B Population structures among epiphytal foraminiferal communities, Nevis, West Indies. Journal of Micropalaeontology, 27: Wilson, B Late Quaternary benthonic foraminifera in a bathyal core from the Leeward Islands, Lesser Antilles, NE Caribbean Sea. Journal of Micropalaeontology, 27: Wilson, B Effect of hurricanes on guilds of nearshore epiphytal foraminifera, Nevis, West Indies. Journal of Foraminiferal Research, 40: Wilson, B The impact of hurricanes on epiphytal Foraminifera on rhizomes of the seagrass Thalassia testudinum, Nevis, north-eastern Caribbean Sea. In: Seagrass: Ecology, Uses and Threats (ed Pirog, R. S.), pp , Nova Science Publishers, Hauppage, New York, USA. Wilson, B., Orchard, K. & Phillip, J SHE Analysis for Biozone Identification among foraminiferal sediment assemblages on reefs and in associated sediment around St. Kitts, Eastern Caribbean Sea, and its environmental significance. Marine Micropaleontology, 82-83: Wilson, B. & Ramsook, A Population densities and diversities of epiphytal foraminifera on nearshore substrates, Nevis, West Indies Journal of Foraminiferal Research, 37: Wilson, B. & Wilson, J. I Shoreline foraminiferal thanatacoenoses around five eastern caribbean islands and their environmental and biogeographic implications. Continental Shelf Research, 31: