The existence of shale oil and gas in rocks of different periods must have an origin somewhere in the natural world – unless it is abiotic. At https://phys.org/print440145555.html … we learn that a massive volcanic flare-up during the Cretaceous era was responsible for some of the deposits. Other deposits such as the Marcellus date to the Ordovician era. Why volcanoes became so active is another problem. The theory is that shale fields in Texas and Montana were created in the Cretaceous and a geologist and his students, out in the field, have discovered evidence of layers of volcanic ash in Cretaceous deposits (close to the shale fields). I did wonder if there was a connection with extinction events but apparently not – or at least not so if you accept the uniformitarian laying down of sedimentary strata. There are for example multiple layers of ash and the theory is there were multiple volcanic outbursts – at intervals of around 10,000 years. At once we are faced with uniformitarian principles of sedimentation. Are these multiple volcanic events justified? Basically, what has been found are rocks with evidence of layers of ash interspersed between layers of other sediment (mud or whatever). They could equally have been laid down rapidly in one single event – a mud and ash flow. In Texas they have this ash layer close to a shale field but does it mean volcanoes were going off in other parts of the world. Well, they have recently found that volcanic island arcs in the Pacific were pretty active at this time.
The really interesting part of the study is how the oil and gas became locked within the shale. These hydrocarbons have to be concentrated in order to make oil and volcanoes emit lots of volatiles including phosphorus and iron. These are eagerly fed on by algae and they create an oxygen starved blooms. When have we herd of this before. chalk.
At https://phys.org/print440150513.html … we stay in the Cretaceous but this time it is the discovery that there was an explosion of diversity in fish after the K/T boundary event. The asteroid strike killed off all the larger marine reptiles and a lot of the sharks and it allowed fish that had been heavily predated to expand their ranges and evolve into new variations in order to fill niche feeding patterns and different areas of the sea. The K/T boundary event killed off 50 per cent of all species worldwide – on land and in the sea. This somewhat like the mammal expansion on the land – which came about as a result of the killing off of its competitors.