The Bell Hill vineyard is sited on a small, bell shaped hill capped with the Amuri Formation limestone.
DR P.J. TONKIN’S SOIL SURVEY OF BELL HILL VINEYARD 2003
GEOLOGICAL AND LANDSCAPE SETTING
The limestone is inclined (dipping) to the west and north and comprises an upper stronger crystallised limestone with a wide fracture spacing, grading to a lower, weaker, finely fractured chalky limestone. The limestones in turn grade to the underlying Waipara Formation which comprises olive yellow to green unconsolidated sands, consolidated sandstones, siltstones and mudstones. The occurrence of these contrasting beds in the Waipara Formation is not predictable from the surface features. Calcareous mudstones (marls) also occur in the transition between the Amuri and Waipara Formations.
The olive yellow to green colours in the lower part of the chalky Amuri Formation and in the underlying Waipara Formation is commonly related to the presence of glauconitic silt to sand sized aggregates of potassium and iron rich mica clays. These aggregates break down on weathering to produce clay loam or clay textured soils. The mica clays include smectite, which if present in sufficient quantities cause the soil mass to shrink and swell on wetting and drying.
DESCRIPTION OF THE SOILS ON BELL HILL VINEYARD
ANTHROPIC SOILS
A direct result of earlier use of the upper part of the northerly aspect as a lime quarry resulted in a cut into the original slope and the distribution of side castings on the slope below the quarry.
The presence of side castings has modified the original soil and the reformed Anthropic soils that have no formal Soil Series name.
WAIKARI SOILS
The unifying feature of the Waikari soils is the presence of; strong limestone, or firm to weak chalky limestone, or calcareous mudstone (marl) below either the A or Bw or Bt horizons where the latter are present. This implies that the deeper subsoils would have an alkaline pH, and are likely to contain active lime.
MELANIC SOILS
(Revised New Zealand soil classification, Hewitt, 1993)
TIMPENDEAN SOILS
The unifying feature of the Timpendean soils is the presence of; olive yellow to green coloured glauconitic sediments of the Waipara Formation below the A and Bw, Bt and Bwk or 2CRk horizons. These sediments vary from unconsolidated sandstones (loamy sands and sands) to slightly calcareous mudstones (marls) and non-calcareous mudstones.
The soils in this block are predominantly shallow Waikari soils, soil profile class Wk1a. These soils typically have a clay loam topsoil (A) of variable thickness overlying fractured limestone.
QUARRY BLOCK
The soils in this block can be defined in three areas, an eastern area in which Waikari soils, soil profile classes Wk2 dominates, a western area in which Waikari soils, soil profile class Wk3 dominates. These soils typically have a clay loam topsoil (A) overlying a structured clayey subsoil (Bt) grading to a chalky subsoil (Bwk or CRk). The Timpendean soils, soil profile class Tm2 dominates in the upper south eastern area. These soils typically have a clay loam topsoil (A) overlying a subsoil (Bw) of variable texture (silt loams to clay loams) grading to slightly calcareous glauconitic sandstone.
THE ROADBLOCK
The upper third of this block are predominantly Timpendean soils, soil profile classes Tm4 – Tm2, and in the lower two thirds predominantly Waikari soils, soil profile classes Wk4 – Wk5 – Wk6. Soil Wk6 formed from calcareous sandstone and therefore has a sandy subsoil.
THE SLOPE
In this block Timpendean soils, soil profile classes Tm5 and Tm6 predominate with subdominant contribtutions of soil profile classes Tm1 and Tm4. Soils Tm5 and Tm6 are distinguished by their thick massive clay to clay loam subsoils (Bt) which overlies glauconitic mudstone. Waikari soils, soil profile classes Wk3, Wk5 and Wk6 occur in the middle and along the southern margin of the block.
LIMEWORKS BLOCK
The soils in the upper two thirds of this block are Earthy Fill Anthropic soils developed in a variable depth of side casting overlying buried Waikari soils. There is a general trend down slope from the south western corner of the block to the north eastern corner, in which the buried Waikari soils grade from soil profile class Wk1a, to a variable pattern of soil profile classes Wk3, Wk4 and Wk5 in the middle part of the block. In the lower (northern) part of the block Waikari soils, soil profile class Wk4 form a strip that extends east into the lowermost part of the adjacent Quarry block. These soils (Wk3, Wk4, Wk5) are distinguished by the thickness and texture of the subsoil (Bw or Bt) varying from clay loams to clays. These subsoils grade into soft chalky limestone or slightly calcareous marl.
