Is the Illawarra Escarpment Part of Australia's Great Dividing Range?

No. The Illawarra Escarpment is a distinct geological feature within the Sydney Basin, not part of the Great Dividing Range.

Illawarra Escarpment:

• Steep coastal cliff line south of Sydney (NSW)
• Runs parallel to coast, rising abruptly to ~750 m
• Forms eastern edge of Illawarra region
• Geology: Hawkesbury Sandstone, Illawarra Coal Measures

Great Dividing Range:

• Massive cordillera ~3,500 km from QLD to VIC
• Located further inland
• Includes Australian Alps, Snowy Mountains, New England Range
• Broader, gentler, multiple sub-ranges

The escarpment marks the coastal margin of the Sydney Basin; the Dividing Range is the continental watershed spine. They're separate systems, though both shape eastern Australia's dramatic topography.