Kimberley Reef Growth and Maintenance

K I M B E R L E Y M A R I N E R E S E A R C H P R O G R A M

WA M S I P R O J E C T 1 . 3 . 1 – P R O F. L I N D S AY C O L L I N S – C U R T I N U N I V E R S I T Y

R E S E A R C H E R S – D R M I C K O ’ L E A R Y, A L E X S T E V E N S

P H D C A N D I D AT E S – G I A D A B U FA R A L E , M O ATA Z KO R D I , T U B A G U S S O L I H U D D I N

T R A D I T I O N A L O W N E R S — B A R D I J AW I , M AYA L A , D A M B I M A N G A R I

Objectives of Project 1.3.1QUESTIONS

• How does reef structure and architecture vary regionally (i.e., inshore

vs. offshore) and comparatively (i.e., Kimberley vs. GBR)?

• How many reefs and island are there in the Kimberley, are they

geographically significant features?

• Do Kimberley reefs represent significant geological structures or more

simple coral communities?

• How rapidly have reefs grown over the Holocene, have types of reef

building corals changed over this period?

• How have factors including; sea levels, extreme tides, turbidity and

subsidence, influenced the style and architecture of Kimberley coral

reefs ?

• How are these factors reflected in communities, “turn of – turn off”

history, ecology and substrates

OBJECTIVES AND METHODS

• Satellite and Aerial Remote Sensing: Mapping

reef geomorphology and substrates, reef and

island perimeters, and Kimberley coastline

• Shallow Water Seismic Surveys: Record internal

reef stratigraphy and architecture to assess reef

growth

• Reef coring and Radiocarbon Dating:

Palaeoecological records and reef age isochrons

• Reef Flat Multibeam Mapping: Quantify reef flat

elevations, reef topography and morphology

Reef Mapping and GeomorphologyMore than 800 Kimberley reefs have been mapped, with 30 mapped in detail.

Extensive Fringing reefs dominate

Reef Mapping and GeomorphologyMultibeam surveys of southern Kimberley reefs with elevated reef flats above MSL

• Highest surveyed reef flat on the east of Tallon Island (1) has a mean elevation of +0.25 m above mean sea level

• On average this reef’s reef flat is exposed for longer then it is submerged!

• This is highly atypical for a coral reef

Reef Mapping and GeomorphologyKey Outcome and Findings

• Kimberley reefs are geographically and geomorphically complex and atypical when compared to other reef systems

• Kimberley reef bioregion, although 1/3 geographic size of the GBR, is almost equivalent in magnitude in terms of the total number of reef and islands

• Kimberley reef morphology data provides a firm scientific foundation for biodiversity assessment and reef structure comparisons.

• ReefKIM provides a dynamic geodatabase of Kimberley Reefs – 30 reefs mapped in detail

New Geomorphic Classification Scheme for Kimberley Coral Reefs

Kimberley Bioregion

Inner Ramp<30m wd

Tides≥9m

Reef Geology and Growth HistoryCockatoo Mine pit provided a complete vertical and horizontal section through a fringing reef

Cockatoo Island, 12/9/2010, 0730. John MacFadyen

Reef Geology and Growth HistoryReef growth initiated 8,500 years ago resulting in 13 m of vertical reef accretion

Cockatoo mine pit section

Cockatoo reef experienced an early period of rapid growth, followed by reduced growth as the reef was drowned, then switched to rapid growth as it reached sea level

Percussion and rotary coring methods

Reef Geology and Growth History54 reef cores from 4 reef sites, reef growth history constrained by 60 radiocarbon coral dates

Reef Geology and Growth HistoryReefs display a range of growth histories - Keep-up, Catch-up and Give-up

Reef geology, stratigraphy and evolutionKey Outcome and Findings

• The Cockatoo Reef study provides the first information on Holocene reef growth for a nearshore reef of the Kimberley Biozone.

• Core study collected first subsurface sedimentary samples for the key types of reef found in the southern Kimberley & sheds considerable light on the growth history of these muddy reefs

• Initiation of coral reef growth in the Kimberley occurred very soon after post glacial flooding of the continental shelf, between 7,000 and 8,500 years ago

• Inshore reefs were able to sustain growth despite highly turbid waters, as indicated by muddy matrix in reef core samples – indicating greater resilience than reefs elsewhere

• Early reef assemblages were dominated by branching coral species, switching to massive and finally coralline algal assemblages as reefs attained sea level

• While high reefs show continual vertical aggradation throughout the Holocene, low reefs appear to have “turned off” with vertical growth stopping between around 5 to 6000 years ago

Internal Reef ArchitectureSeismic (sub-bottom) architecture of southern Kimberley reef systems

AAE AA201 Boomer SBP system

Sunday and Tallon Island 42 km

Cockatoo Island 31 km

Bathurst and Irvine Island 49 km

Montgomery and Station reefs 53 km

Molema Island and Turtle Reef 55 km

Adele Island and Churchill Reef 50 km

Brue Reef 13 km

Total 294 km

Internal Reef ArchitectureCorrelation of seismic reflectors and stratigraphic and geological core data

LI Reef= top of Last Interglacial Pleistocene reef (MIS 5); Holocence Reef = Last 12,000 years.

Un-interpreted Section

High Intertidal Planar Reef: Montgomery

Central Proterozoic island surrounded by sand sheet, upper and lower terrace lagoons with rhodolith banks, crustose coralline algae and pools with corals

• Two reef buildups:

LIG reef ( ̴ 10 m thick)

Holocene reef ( ̴ 22 m thick)} Terracing of the forereef

Forereef geomorphology reflects reef building stages

SOLEOL

R1 = top of LIG Pleistocene reef RF = Proterozoic rock foundation

The Breakwater (Montgomery)

• Pinnacle reefs of different level of maturity (N-S, 3 stages):

A. LIG: marginal pinnacles and central coalescent (juvenile)

B. Incipient Holocene colonisation of LIG pinnacle reefs (intermediate)

C. Two stacked generations (LIG and Holocene) of pinnacle reef (mature)

• Thick sediment drapes

Hol = Holocene Reflector

R1 = top of LIG Pleistocene reef

RF = Proterozoic rock foundation

Platform Reef: Adele Reef

•Min of 3 stages of reef platform buildup:Holocene (> 20 m)

Last Interglacial (5 m)

Penultimate Interglacial (~ 20 m)

•Pinnacle reefs active reef margin growth

SOLEOL

Kimberley Reef Seismic StratigraphyKey Outcome and Findings

• First Seismic study in the southern Kimberley

• Supports reef core data - Kimberley reefs are significant geological structures

• Holocene reef growth initiated over antecedent highs particularly older fossil reefs

• Evidence reef growth occurred during past interglacial periods and therefore not unique to the Holocene – at least 3 stages of growth offshore, 2 onshore.

• Long term resilience – challenging environmental conditions and oscillating sea levels.

Management Applications• Produced a reef classification scheme for the Kimberley Bioregion

• Produced GIS database (ReefKIM), which includes georeferenced data and location of every significant reef in the Kimberley (Landsat resolution =30m)

• ReefKIM database can be used as the primary platform for all further reef census data

• ReefKIM already includes detailed substrate & geomorphology maps for 30 Kimberley reefs

• Many Kimberley reefs are atypical and the ReefKIM database can be used to highlight those with a high conservation value

• Seismic and reef core data show Kimberley reefs to be robust on geological timescales i.e., record reefs surviving and evolving within ever changing environments

• Findings Suggests that despite extreme environmental conditions including; (1) high turbidity and sediment input, (2) elevated water temperatures, (3) extreme tides, (4) significant subaerial exposure during low tides, and (5) frequent cyclones, reefs can endure, survive and thrive in the Kimberley

OutputsPapers – 3 published, 1 in review, 1 in prep

Published

• Solihuddin, T., Collins, L.B., Blakeway, D., O’Leary, M.J., 2015. Holocene Reef Growth and Sea Level in a Macrotidal, High Turbidity Setting: Cockatoo Island, Kimberley Bioregion, Northwest Australia. Marine Geology. Volume 359, pp 50–60

• Collins, L.B., O’Leary, M.J., Stevens, A. M., Bufarale, G., Kordi, M., Solihuddin, T, submitted. Geomorphic Patterns, internal architecture and Reef Growth in a macrotidal, high turbidity setting of coral reefs from the Kimberley Bioregion. Australian Journal of Maritime & Ocean Affairs. To be published April 2015

• Richards, Z.T., and O’Leary, M.J., 2015. The Coralline Algal Cascades of Tallon Island (Jalan) Fringing Reef, NW Australia. Coral Reefs. Online

In review

• Bufarale, G., Collins, L.B., O’Leary, M.J., Stevens, A. M., Kordi, M., Solihuddin, T., submitted. Geomorphology, internal architecture and growth patterns of macrotidal reefs of the Kimberley Biozone, Northwest Australia. Marine Geology.

In preparation

• Kordi, M., Collins, L.B., Stevens, A. M., In Prep. Geomorphic Patterns, Habitats and Substrates of Macrotidal Reefs from the Kimberley, NW Australia.

Presentations and Posters – 6 Presentations, 2 posters

• Royal Society of Western Australia’s Centenary Postgraduate Symposium: 2 presentations – presentation award (T. Solihuddin).

• Coast to Coast Conference, Mandurah, October 2014: 2 presentations, 2 posters – poster award (G. Bufarale).

• Research Colloquium Marine & Coastal Resources - Research & Development Center for Marine & Coastal Resources Indonesia: presentation

• Trimble Dimension, Las Vegas: presentation

• AAPG/SEG/PESA 2015 International Conference & Exhibition: presentation

• TO Presentations – Mayala, Bardi Jawi, Dambimangari

5 Milestone Reports completed, Reports to TO’s completed, submitted, Collaborations: UWA, WAM.

AcknowledgmentsThe State Government of Western Australia and WAMSI partners, in particular Curtin University, for funding this research.

Kimberley Marine Research Station and Cygnet Bay Pearl Farm, James Brown and Erin McGinty

Barry Wilson (expert reviewer), Clay Bryce, WAM (ground truth data), Pluton Resources (Mine Access), David Blakeway (MScience, fieldwork assistance)

CMST (Iain Parnum for swath mapping assistance)

Traditional Owners - Bardi Jawi, Dambimangari, Mayala

Kimberley Media for access to images

Future Work Is the unique southern Kimberley reef morphology and growth history a function of the broader Kimberley biogeographic region, or driven at a local level by the extreme tidal amplitudes?