SEDIMENTOLOGY

SEA TO SHORE

Watercolour on paper,
70cm x 60cm

The bottom blues represent a deep marine environment passing up into shallower
water sediments.

Above the bottom blue zone a black mud has settled into troughs of ripples
leaving a set of arrow shapes pointing down.

The orange colours are cross bedded sandstone with the two bottom beds being
transported from left to right. Then the transport direction reverses and travels
right to left. The sands may have been deposited by a meandering river emptying
into the sea and forming a coastal plain.

Finally, the tan lagoonal muds at the top are filled in with plant matter that is later
converted into coal.

FLAIRS TO QUICKSAND

Watercolour on paper,
70cm x 60cm

The cool blue colours represent sediments that have been deposited under water.
The warm oranges and browns are sediments that have been rapidly slumped
from shallow water into deep.

At the bottom are the blue/black “flame” structures where sand has weighed down
on the dark blue mud and squeezed it up into “flame” like structures. Mud
deposition returns several times before it is interrupted by a large slump from
shallow water. The slump may have been caused by an out-building delta or an
earthquake. In any event, the orange and brown sediments have been deposited
so quickly that not all the water escaped. This slumping, coupled with the later
dewatering, produces soft sediment folds and thrusts that are completely different
in shape and form to the sediment above and below them. At the top sits a cross
bedded, bluish sandstone with current running from right to left

EMPIRE OF THE SILICEOUS OOZE

Acrylic on canvas
61cm x 76cm

Chert or flint comes from a deep sea “factory” that takes micro-organisms and turns them into a hard, siliceous rock.

A pelagic, deep-sea sediment containing marine zooplankton (in this case Radiolarians) forms a biogenic, amorphous opal on the seabed – the siliceous ooze. Then through compaction, cementation, reworking, replacement, crystallisation, leaching, hydration, bacterial action (and a few others I haven’t thought of) the ooze transforms into disordered, crystalline opal. Further physical and chemical changes eventually convert the crystalline opal into a mosaic of microcrystalline chert (the grey areas) or chalcedony.