A Bunch of Coconuts

Coconuts on the tree at Port Douglas, Four Mile Beach.

To most of us who are unfamiliar with the natural world of the tropics, coconuts are the small brown hard hairy things that you very rarely buy in the supermarket, or maybe have tried once in a blue moon to hit on a coconut shy at the fair. A song springs to mind:

I’ve got a lovely bunch of coconuts
There they are, all standing in a row
Big ones, small ones, some as big as your head
Give them a twist a flick of the wrist
That’s what the showman said.
I’ve got a lovely bunch of coconuts
Every ball you throw will make me rich
There stands my wife, the idol of me life
Singing roll a bowl a ball a penny a pitch …..

Fred Heatherton

The reality, of course, is that the fruits of the Coconut Palm (Cocos nucifera) look very different at the point of origin, as I found out on a visit to the north Queensland palm-fringed tropical coast some years back. They do come in all sizes in their own wrapper – including a smooth outer shell, which varies from yellow, to green, to brown, according to age.

The thick fibrous layer between the outer cover and the nut itself helps the coconuts to disperse by allowing them to float and travel long distances at sea. I found coconuts on the beach with stalked or goose barnacles attached – indicating that they had been in the water for some time before washing ashore again.

Other coconuts lying on the sand have strange characteristic holes in them, gnawed by the nocturnal White-tailed Rat (Uromys caudimaculatus) that chews right through all the hard layers to get to the white flesh inside. And coconuts are still in great demand as the basis for exotic beach-side cocktails even in far-away and isolated places, as evidenced by a barrow-load of them in the shade near a bistro hidden among the trees at Cape Tribulation.

Black Parrots and Beach Almonds

Close up detail of the fibrous inner husk of a Beach Almond

I found several small, fibrous, ovoid husks washed up on the shore at Trinity Beach and Normanby Island when I visited Queensland in Australia; and I wondered what they were. Sometimes, the fibres were still covered and contained by a tough leathery blackened skin with an unusual keel extending around the perimeter of the fruit. They had obviously lain on the beach and floated in the sea for quite a time. I couldn’t work out what they were.

It was not until I was enjoying a cold drink at a beach-side cafe in Port Douglas that I found the answer. A ruckus drew my attention to a tree in which a group of black parrots were noisily squabbling over fruits. Clusters of bright green fruits of the same peculiar shape and size as the flotsam specimens were growing high on the branches and also lay scattered whole, opened, or half-eaten on the ground where the parrots had dropped them. They were Beach Almonds.

The fruits belong to a family of trees (Combretaceae) common in the tropics. The Genus Terminalia has about 200 species, and I think it likely that the fruits I found were from one of the three most common species on the beaches of northern Queensland, Terminalia catappa, T. arenicola, or T. seriocarpa. The fruits are described as being canoe-shaped and ripening from green to blue-purple.

Rocks at Port Douglas, Queensland

These are some personal observations, just thinking aloud, and part of my learning process and fascination with geology. I have a lot of questions to ask about the rocks at Port Douglas on the Queensland coast in Australia! They are marked by a GeoCache site which says they are a batholith. A batholith is formed deep under the earth’s crust where molten magma from superheated, melted rocks, cools slowly and forms granite made up of fairly large crystals. In eastern Australia the batholith formations, known collectively as the Kennedy Province, were created between 330 and 255 million years ago  – following the earlier formation of the Hodgkinson Province which was created between 440 and 360 million years ago, and into which the batholith magma eventually intruded.

I have seen a batholith before – at Peggy’s Cove in Nova Scotia – and the the rocks I photographed at Port Douglas are very different from the rocks exposed at Peggy’s Cove – at least the ones around the edges of the formation in Port Douglas, notwithstanding that the two outcrops of bedrock are in two separate continents and have been subjected to very different erosional and weathering processes. Peggy’s Cove rocks have been smoothed and polished by ice sheets (glaciated) and their surfaces remain clean in a temperate climate. At Port Douglas, on the other hand, the rocks have eroded out and weathered in the wet tropics climate which has led to different erosional characteristics and a surface obscured in many parts by black bio-film.

Batholiths are made of granite. I think I can see granite in some areas of the Port Douglas outcrop on which the Lookout stands. A lot of what I believe to be granite is covered in black biofilm (possilbly cyanobacteria and lichen) and is colonised by organisms like barnacles so that the details are obscured. However, most of the detailed close-up shots I took of the rocks, particularly those around the edges of the feature, including loose boulder lying on the waters’ edge, did not seem at all like granite to me. There are various colours, textures and features as shown in the photographs in this post. I have been wondering to myself, speculating, whether these rocks may represent the junction between the granite of the Kennedy Province batholith and the Hodgkinson Province rocks into which they intruded, showing further changes to the earlier overlying (and already much altered, stretched, compressed and vulcanised) metasedimentary rocks.

The geological map of the area describes the outcrop of bedrock in the Port Douglas environs as Larramore Metabasalt Member which is part of the Hodgkinson Province rocks. I suspect that some of my photographs may be showing these metabasaltic rocks, or metasedimentary rocks with evidence for explosive volcanic activity and volcanic intrusions. I have read Rocks, Landscapes and Resources of the Wet Tropics by Berndt Lottermoser et al (2008) published by the Geological Society of Australia, Queensland Division, and have found it very useful. However, a more relevant account of the port Douglas geology might be given in another book which I have been trying to track down: Rocks and Landscapes of the Cairns District by W. F. Willmott and P. J. Stephenson (1989) published by The Queensland Department of Mines and Energy but it is out of print. I think it might be useful in helping me answer some of the questions I’m posing.

Tribulation Drift

Abstract natural patterns of coral sand and plant debris on the drift line at Cape Tribulation beach

I like these abstract natural patterns that I photographed several years ago on the beach at Cape Tribulation in Northern Queensland, Australia. I have seen similar nearer to home, on Studland Beach in Dorset, England. Complex dendritic or branching drainage channels, where water has flowed down the shore with the ebbing tide, cut through a surface layer of much-comminuted dark brown flotsam plant debris, leaving designs of white contrasting coral sand.

Abstract natural patterns of coral sand and plant debris on the drift line at Cape Tribulation beach

Abstract natural patterns of coral sand and plant debris on the drift line at Cape Tribulation beach

Abstract natural patterns of coral sand and plant debris on the drift line at Cape Tribulation beach

Abstract natural patterns of coral sand and plant debris on the drift line at Cape Tribulation beach

General view of Cape tribulation beach with driftline of fine particle plant debris

Seashells on Normanby Island – Part 2

I enjoyed my first visit to Normanby Island so much that I went back a second time before I finished my Queensland holiday – and photographed some more seashells!

P.S. This is the 1000th Post I have published on Jessica’s Nature Blog.


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