#ooid

Ooids in thin section.

The beach at Baleal Baleal, today a small piece of rock attached to mainland Portugal by an isthmus, takes its name from Baleia, the Portuguese word for whale. Centuries ago, this location was a site where hunted whales were brought for butchering. Today it is one of Portugal’s surfing hotspots as the combination of ocean currents and geologic features funnels waves perfectly into the coast.

OOIDS

One of my favorite sedimentary rock features, ooids. These are small, rounded grains of calcium carbonate, usually 1-2 millimeters in diameter.

Ooids are like coated sand grains. They form in areas where carbonate minerals are readily precipitating, such as warm, tropical oceanic waters. They need a core to start off growth, usually a sand sized grain of sediment or shell fragment. As those grains are tossed around by the waves, typically in a beach or near shore setting, newly formed carbonate minerals grow around the edges. The action of the waves rolls the grains, mostly keeping them from sticking together and allowing them to grow on all sides, forming these nice little spheres.

You’ll sometimes find entire rocks made of these known as oolitic limestones, and in fact there’s even a small town named Oolitic in Indiana (although residents always told me they pronounced the word different, with a long O sound in the name of the town).

-JBB

Image credit: https://flic.kr/p/8EsGdG

Cleopatra's beach

The sand you see here gracing this rather ordinary beach on the Turkish island of Sedir did not originate here, and was not brought to its resting place by the action of waves or other natural forces but by the hand of man some 2,000 years ago in antiquity recording a romance that has fascinated people including Shakespeare, which is why this sand is protected by the government.During the civil war that followed the assassination of Julius Caesar on the Ides of March Octavian (soon to become better known as the first emperor Augustus) was pitted against Marcus Antonius and his ally Cleopatra, ending in his victory over the ill fated couple at the battle of Actium.

The sand is made out of limey oolites, formed when supersaturated water starts to form a kind of natural pearly as grains roll in the waves and have calcium carbonate precipitated in layers over their central nuclei (see https://bit.ly/1WHE33i). They were transported by ship (legend says 16 large barge loads were needed) and hard graft from Egypt to make a perfect bathing spot for the amorous pair. The ruins of their local palace lie on the hillside opposite, and it may have been linked to the beach by a secret tunnel. Analysis has shows them to be identical to those on beaches west of Alexandria, at the time their main base, demonstrating that legend often contains a kernel of truth, however distorted and partially forgotten. .

Loz

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