Margaret River GI

Technical Summary

• Classification: GI (Geographical Indication)
• Legal status: Protected geographic indication under Australian wine law
• Country: Australia
• State: Western Australia
• Zone: South West Australia
• Area under vine: ~5,500 hectares
• Core products: Cabernet Sauvignon; Chardonnay; SBS (Semillon/Sauvignon Blanc) blends

Climate Profile:

• Mediterranean with strong maritime influence
• Indian Ocean to west; Southern Ocean to south
• Compared to Bordeaux in temperature and rainfall
• Low diurnal range (ocean moderation)

Verified Constraints:

• Minimum 85% from GI for geographic claims
• Minimum 85% for varietal claims
• Quality standards voluntary; no yield limits

Regulatory Constraints (Verified)

GI Requirements (Australian Wine Law)

Geographic labeling:

• Minimum 85% grapes from Margaret River GI

Varietal labeling:

• Minimum 85% of named variety

Vintage labeling:

• Minimum 85% from stated vintage

Yield (No Federal Limits)

• Producer discretion
• Quality focus: 4-8 tons/ha typical
• Premium: 3-5 tons/ha
• No regulatory maximum

Geographic Scope

Margaret River GI encompasses:

• Narrow peninsula between capes
• Approximately 100km north-south; 27km average width
• Bounded by Indian Ocean (west) and Southern Ocean (south)
• Rainfall: 1,000-1,200mm annual (winter-dominant)

Key Varieties and Styles

Cabernet Sauvignon (Benchmark)

• Primary red variety (~40% of production)
• Bordeaux-like elegance with Australian intensity
• Often blended with Merlot, Cabernet Franc, Petit Verdot
• Oak aging standard; French oak dominant

Chardonnay (Benchmark)

• Primary white variety (~25% of production)
• Burgundian approach increasingly common
• Balance of fruit and acidity
• Variable oak treatment (barrel-fermented to unoaked)

SSB / SBS Blends

• Sauvignon Blanc + Semillon blends
• Margaret River specialty (Bordeaux blanc style)
• Textured, age-worthy whites
• Typically 50-60% Semillon, 40-50% Sauvignon Blanc

Enological Implications

Evidence-backed:

• Cabernet Sauvignon achieves full phenolic ripeness with moderate alcohol (13-14.5%)
• Maritime influence provides even growing season
• Chardonnay retains acidity; natural MLF management possible
• Low Botrytis pressure (dry autumn)
• Extended growing season (late March-April harvest)

Operational observation:

• French oak dominant for premium wines
• Whole-berry fermentation common for Cabernet
• Natural acidity higher than Barossa Valley or Napa
• Modest alcohol levels compared to warmer Australian regions
• Reductive handling for white varieties

Frequent Compliance Risks

• Geographic claims: 85% from Margaret River GI required
• Varietal accuracy: 85% minimum for named variety
• Blend claims: “SSB” or “Classic Dry White” conventions (not regulated)
• Organic/Sustainable: Certification requirements if claimed
• Vintage claims: 85% from stated vintage

Sub-regional Diversity

Northern Margaret River:

• Warmer; slightly earlier ripening
• Fuller-bodied wines

Wallcliffe (Central):

• Core region; moderate climate
• Balance of structure and elegance

Southern Margaret River:

• Coolest; most maritime
• Higher acid retention; elegant wines

Relevant Grape Varieties

• Cabernet Sauvignon - benchmark red variety
• Chardonnay - benchmark white variety
• Sauvignon Blanc - SSB blend component
• Semillon - SSB blend component
• Merlot - Bordeaux blend component

References

• Wine Australia (2024). “Geographic Indications - Margaret River.” https://www.wineaustralia.com

• Margaret River Wine Region (2024). https://www.margaretriver.com

• Halliday, J. (2024). “Australian Wine Companion.” Hardie Grant Books. Link

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Last Updated: January 6, 2026