Gulf of Mexico Geology

10 May 2019

At ...  a research paper in Scientific Reports (May 7th 2019) says that complex geology in the Gulf of Mexico contributed to the Deepwater Horizin disaster. Most commentators have, to date, concentrated on the engineering decisions that led to the bow out or the ecological consequences of the oil spill. The new paper tells the geological tale behind the catastrophe and is well worth a read - if only to grasp the complexity of what is involved in deep drilling and how easy it must to be to secure a blow out rather than a gusher. At the same time, the sheer cleverness of the oil people is mind boggling. Most of us go through life without being troubled by too many challenges in the work place but these guys face challenges all the time.

A couple of days later there was a post on the Gulf and Oil at ... which concerned the gas extraction offshore of Louisiana and Texas (and somewhat later, oil). The title, how climate change buried a desert 20.000 feet beneath the Gulf of Mexico seafloor, caught my eye, as it would, and pretty well sums up how geology in one place is quite different from another place. The author, David Middleton, is a geologist and regularly posts at Anthony's blog, usually with a strong mainstream streak in anything he discusses (apart from climate change as he is a denier in that subject). He also describes in some detail the complexities of the geology, particularly concerning the Norphlet formation, which is described as Oxfordian. In the UK this would correspond with the belt of Oxford clay which runs across the South Midlands. It too is Jurassic. However, in England it is at the surface in a wide corridor where the overlying geology has been washed away (either by glaciation or by water). In the Gulf it is buried under many geological layers post dating the Jurassic.

The Norphlet formation was first explored by Mobile Oil in 1979 (yielding natural gas). Some 20 gas fields were subsequently drilled and somewhat later, oil was discovered. The Norphlet formation was laid down 150 to 155 million years ago in a salt filled desert basin, he assures us. This later became the Gulf. It was a complex of sand dunes - but further north, on what is now land, it was deposited as alluvium (which normally equates with a watery origin, rivers or lakes and that sort of thing, rather than anything dramatic, he says). The sand dunes are as deep as 20 to 30,000 feet below sea level - so how did it get there. He then goes on to describe the mainstream view of deposition of sand and how geologists know it was a former desert (without explaining where all the sand originated as sand is usually said to derive from erosion of rocks, ground down to fine particles). Was it eroded or was it dredged up from the bowels of the Earth? This Jurassic formation was subsequently covered by Cretaceous, Paleogene, Eocene, Oligocene, Miocene and Plaeistocene geological layers, which are related, he says, to sea level cycles - amongst other things. So, what happened to all this subsequent geology in Britain?