30 Mar 2016

Upper beach seaweed, early spring.

Green Ascophyllum nodosum (knotted wrack) in full reproductive swing; the spotted lighter sacs are the conceptacles, the seaweed's reproductive organs. The wispy red algae is Polysiphonia lanosa which lives as a hemiparasite on the Ascophyllum. 
 

The Bay yesterday was looking rather splendid:


It was an Easter holiday ramble of the beach with the youngest field assistant, but we found a couple of Gryphaea, extinct Jurassic oysters:
The right hand specimen has a small, almost complete Gryphaea on the left hand side, the rest is made up of smaller specimens. I've been reading a dissertation of the Jurassic geology of this area which talks about anoxic events; periods when the seabed became inundated with dexoygenated water, killing whatever creatures got in its way. When you see large numbers of fossils dead together, an influx of anoxic water or getting caught up in a mudslide might be the cause. Some Jurassic creatures found as fossils in Runswick beach thrived in low-oxygen conditions such as these Pseudomytilus dubius, bivalve molluscs. These ones are rather splendidly pyritized (coated in fool's gold) on the outside of a pyritic nodule.


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