Thursday 24 February 2022

The Cretaceous Ended in Springtime!

The Cretaceous Ended in Springtime! 

THIS ARTICLE gives convincing evidence that the Cretaceous ended on a spring day. I am not sure whether it was morning or evening.

It is based on THIS PAPER in which the authors, studying fish fossils, speculate that bone growth had just restarted after a winter pause. The fish had died while ingesting spherules caused by the asteroid impact at Chicxulub - within hours of the impact. 

To get a more easily digested summary of their findings I recommend THIS PODCAST by one of the papers authors, Jan Smit. The illustrations supporting the podcast are superb.

Another podcast on this comes from Nature. You can find it HERE. The lead author of the original paper, Melanie During, talks about the selectivity of the extinction - creatures on the surface died, those in burrows escaped. So maybe it happened at night!?

Maps of the Tanis site in North Dakota.  A: Regional context showing the large sea covering central North America during the Cretaceous.  The map shows previously known tsunami locations (black dots) and the Tanis site (star) on an ancient river draining into the inland sea.  B: Photo and interpretation showing the 2.5-meter-thick surge event deposit overlying sandstone deposited as a point-bar in the Tanis river.  C: Diagram (not to scale) of the event deposit setting.  The event deposit (1) covers the slope of a sandy bar of a meander (2).  The densest carcass accumulations (3) were found just below Cretaceous-Paleogene boundary deposits (4) that directly overlay the event deposit.

DePalma et al., PNAS, (2019) 116, 8190

Saturday 19 February 2022

Landslides in Brazil

Landslides in Brazil 

One of my favourite web sites - - has produced three articles about the recent landslides in Brazil. You can see them HERE, HERE and HERE. This is not particularly geological but still fascinating. 

The lesson I take is do not build your house on a steep slope where there is heavy rainfall! Looking at the videos one realises that these are not slums but fairly well off areas - lots of cars, mobile phones. 

The cause of the landslides was extraordinarly heavy rainfall rates of more than 100mm per hour were recorded.

Friday 11 February 2022

Tongan Volcano Poses Questions

Tongan Volcano Poses Questions 

The recent eruption in Tonga did not last long but it has posed several questions which vulcanologists are having difficulty in answering.

THIS ARTICLE reviews the topics. 

  • The power of the blast was extraordinary.

  • The amount of ash is small given the size of the blast.

  • The eruption happened underwater but had a plume which reached the stratosphere.

  • The amount of SO₂ ejected is rather low.

  • The eruption sent waves rippling through the oceans and the atmosphere.

The Hunga Tonga–Hunga Ha‘apai explosion was captured by several Earth-observing satellites.Credit: Visible Earth/NASA

The article tries to give answers for these observations but remarks that the true story will take many years to emerge.

Saturday 5 February 2022

Down to Earth Extra February 2022

Down to Earth Extra February 2022 

The february 2022 edition of Down to Earth Extra has been published. You can get it HERE. Or you can read it below.

Down to Earth 118

Down to Earth 118 

Edition 118 of Down to Earth has been published. You can get it HERE. Or you can read it below.

Friday 4 February 2022

A Nick Chidlaw Field Course

A Nick Chidlaw Field Course 

Nick Chidlaw wants to hold a one day Field Course in the Mendips on the 12th March and would like to know the level of interest. These courses have a great reputation and this one sounds pretty good! All the details Nick has sent me are given below.


I am proposing to run the above next month if there is sufficient interest and availability to make the course viable. I have run the course before, and was gratified attendees indicated that they enjoyed the proceedings and learned a lot.

Course date: Saturday 12th March. The course would run 10.00 am - 5.00 pm. Course fee is £30.00 per person.

No prior knowledge of geology or the study area is assumed.  Attendees will be covered by insurance during the duration of the course. 

If you / anyone else you know would like to attend, please forward a cheque to me at the address below. If you would prefer bank trans, I can send you details. 

8, Silver Street,
GL11 4ND.  

There is a handout that those enrolled would receive in advance of the course, so they can read up about what will be covered and be in a good position to get the most out of the day when it runs. The handout has numerous colour images in it; due to printing costs, I can email you a Word Doc with the coloured images in that you can print out yourself and bring the printout to the course; otherwise I can post you a black and white printout, which is perfectly serviceable. 

Do let me know if you would like to receive the Word Doc which you would print out in colour yourself. 
If you wish to have the black and white printout instead, do let me know and provide me with your postal address, so I can send this to you a week or two before the course is due to run.    

Viability Deadline
The deadline for the minimum number of enrolments (10) is Saturday 26th February.  Maximum number of enrolments on the course is 30.  If the minimum of enrolments is reached by 26th February, arrangements will continue; if not, the course will be cancelled and fees returned soon after. If the course is viable, enrolments can continue up to 1 week (Saturday 5th March) before the course date.  

Please see details below. I hope the course is of interest and to hear from you soon. 


Nick Chidlaw


ASPECTS OF MENDIP GEOLOGY: Early Carboniferous open shelf seas, Late Carboniferous rivers, metalliferous mineralisation in the Jurassic 

The Mendip Hills, rising to 325m above sea level, and located in the counties of Somerset and North Somerset in the west of England, are underlain by mostly sedimentary rocks and mostly of Devonian, Early Carboniferous and Triassic age. They record deposition as the British crust moved slowly northwards from the southern tropics, across the equator, and into the northern tropics. Rivers laid down deposits during Devonian times, and in the Carboniferous, marine environments were present, followed by coal forests on delta and river plains. At the end of the Carboniferous, about 300 million years ago, the British crust was involved in a major plate tectonic collision, known as the Variscan Orogeny: the once-horizontally lying Devonian and Carboniferous strata were pushed up into a series of enormous dome structures elongated east - west, producing a mountainous terrain. By Mid Triassic times, about 240 million years ago, the mountains had been much worn down and coarse bouldery and sandy deposits were being laid down in wadis and valleys, eventually building up to bury the Mendip area. In the following Jurassic period, more sediments were laid down on top, in marine environments. In Middle Jurassic times about 170 million years ago, crustal stretching opened fissures in the Mendip area, up which hot metal-bearing fluids rose from deeper in the crust, cooled and crystallised. The metals included lead ore, of much importance subsequently to mankind. The nature of the ore deposits enabled the first large scale workings (opencasting by the Romans) to be highly productive, but later in time the ores were found to become more scarce at depth. Historic mining records refer to the ore occurring as 'stones of lead', and uncertainty of what exactly this meant was finally resolved by Mendip cave explorers in the 1980's.  

This course examines evidence for the shallow tropical sea at extensive exposures in the rocky dry valley of Burrington Coombe, and discusses the lead mineralisation at Ubley Warren on the Mendip plateau (no lead ore can be seen in exposures now); the final part of the day visits the Deep Leap Reserve on the Hills above Wells, where Late Carboniferous sandstones equivalent in age to the Millstone Grit of the Pennines can be examined.     

Former lead ore opencast workings at Ubley Warren on the Mendips.