The oldest rocks in the Mornington Peninsula are those deposited under deep marine conditions during the Palaeozoic era dating from the Ordovician period (510 to 435 million years ago) and the Silurian period (435 to 405 million years ago). After these were deposited, a period of uplift, folding and faulting took place and the deep sea was replaced by a shallow sea and later by dry land.
During the late Devonian period (about 370 million years ago), granitic intrusions, or former molten material, worked its way through the Palaeozoic rocks. The granitic rocks that occur at Mt Eliza, Mt Martha and Arthur’s Seat were once deep below the surface and have been exposed by subsequent erosion.
The next oldest rocks on the Mornington Peninsula are the basaltic rocks extruded during the Tertiary period (55 to 33 million years ago).
The earliest Tertiary sediments are found near the top of Arthur’s Seat, where there are quartz pebbles and stones in the surface soil and the clay subsoil. Most of the Tertiary sediments date from the Miocene epoch (23 to 5 million years ago) to early Pliocene epoch (about 5 million years ago) and comprise ferruginous gravel, sand and clays.
The youngest sediments are those developed on Quaternary sediments. These comprise alluvium from creeks and drainage lines, dune-fields and coastal dunes dating from the early Pleistocene to the present day.
Soils and Landforms of the Mornington Peninsula
(source Department of Primary Industry)
Of particular interest to us in Main Ridge are the basaltic rocks extruded during the Tertiary period when basaltic lava flows were erupted over much of the eastern half of Victoria, covering fluvial gravel and sand deposits. Around Main Ridge the residuals of these basaltic flows cover an area of about 100 square kilometres and form a broad plateau that gradually slopes towards the south-west from about 200m to 100m terminated by prominent cliffs at Bass Strait. Elsewhere in the Peninsula these residuals are deeply buried.
Compared to other rocks found on Earth’s surface, basalts weather relatively fast; they weather down into relatively neutral and highly fertile red (due to iron oxide) loamy soils called ferrosols (previously known as krasnozems - Russian for red earth). So typical soils here are red ferrosols (deep, friable, red, porous soils with a high free iron oxide content which have moderate to high chemical fertility and water-holding capacity) with dermosols (similar to ferrosols but lacking the high free iron oxide content) over tertiary basalts. Decomposing basalt is generally, but not always, deeper than 1.8 metres depth. (A good place to see the underlying basalt at the surface is on the point at Shoreham Beach.)
See details of our individual vineyards for any specific soil variations.
We believe the way soil interacts with water is how it makes its contribution to terroir. Soil, how it drains, how it retains moisture, works intimately with rainfall patterns to determine whether the vines receive what they need when they need it; the two are inextricably linked and cannot be considered in isolation. Soil controls how water is made available to the vine.
The Peninsula’s pattern of good winter and spring rains and a relatively dry summer works perfectly with our soil’s ability to store winter and spring rain through summer; we irrigate very rarely, certainly not in a “normal” year. Burgundy’s rainfall, in contrast, is much more evenly distributed throughout the year and therefore requires the much more freely draining limestone soils. (See Climate for more information on the Peninsula's rainfall.)