The Natural History of Flint

(This blog is the first from Jeff Stephenson, head of Bowles & Wyer’s Aftercare and Gardening division)

From a driveway on the outskirts of Berkhamsted to the chalk seas of the Upper Cretaceous;

When you walk into a garden, do you ever think about where everything originated from? You might find plants from such diverse places as the swamps and wetlands of the Kamchatka Peninsula (e.g. Lysichiton camtschatcensis), the prairies of eastern North America (e.g. Echinacea purpurea) or the coastal forests of Chile (e.g. Fascicularia bicolor). That’s just the chlorophyll containing contingency; what about the supporting cast of hard features; decking materials, manufactured corten steel edgings and natural stones?

In this blog I’m going to concentrate on one of the most unglamorous and overlooked materials we use in gardens. It has been a mainstay material for infilling drainage channels, adding to compost mixes, covering driveways and paths or incorporating into traditionally crafted, regional, walls.  I’m going to share with you what I know about flint. Before I took up horticulture, long before I joined Bowles & Wyer, I studied natural sciences; geology was and still is a particular interest of mine; so when I go into gardens I’m not just thinking about gardening, I’ve also got one eye out for the past; the vast expanse of the geological past.

Flint driveway in a Hertfordshire garden.
Knapped flint wall in a garden in Berkshire.

The flint that you would handle as a landscaper has much more dynamic origins then simply being extracted, graded and bagged. It originates way, way back, over 65-90 million years (Ma) ago during the Late Cretaceous Period; a time when, on land, Tyrannosaurus rex was stalking it’s prey, ancient bees were pollinating the first flowering plants; and in the sea, gigantic mosasaurs swam amongst ammonites and sharks.

What is flint? 

This is the scientific bit; Flint is a particular type of chert that is specifically found in the chalk deposits of the Upper Cretaceous. It is made from the mineral chalcedony, an opaque, unified coloured and cryptocrystalline (micro crystal) form of silica.

What is chalk?

To talk fully about flint, I first have to discuss it’s bedfellow chalk. Have you ever walked atop the White Cliffs of Dover or around Beachy Head? Well the rock you’re standing on is chalk. If you were to take a piece of this chalk, crush it and view the pieces under a microscope you’d find rather unusual disc shaped structures called coccoliths. These were once part of tiny spherical units called coccospheres; the hard calcareous (calcium carbonate) skeletons of billions of microscopic organisms called coccolithophores, a type of marine plankton (they can still be found in parts of the oceans today).

They lived in the upper sunlit reaches of the Cretaceous sea. During this time the supercontinent Pangaea was breaking apart and volcanic activity was producing greenhouse gases which, through increasing global temperatures, prevented the formation of polar ice; leading to elevated sea levels.  As they died they would have ‘rained’ down onto the sea floor forming a lime mud. These sediments eventually compacted into chalk.

Sponge spicules under a light microscope.
Scanning Electron Micrograph of Coccolith plates in Upper Cretaceous Chalk.

How did the flint form in the chalk?

Take a closer look at those chalk cliffs; interspersed in dark hard bands you will find the garden familiar flint.  But where did it come from? From a rather unexpected source. Living on the ancient sea floor were sponges whose bodies contained silica in the form of tiny needle like structures called spicules.  It is mainly the silica from these spicules which, upon the death and burial of the sponges, broke down and enriched the water in the pore spaces of the buried sediments.

These siliceous rich waters then migrated along bedding planes and precipitated out in burrows made by the activity of organisms such as shellfish, sea urchins and worms. Over time and with further burial this material becomes flint. Millions of years of this cyclical process led to the accumulation of chalk deposits within which regular flint bands are found.

How did the flint get separated?

This is where plate tectonics comes in; movements of the earth’s plates (leading to the formation of the Alps) caused the uplift and exposure of these deposits which were then subjected to weathering and erosion. The chalk degrades but the hard resistant flint material gets eroded and re-deposited a number of times through the activity of seas, rivers and glaciers and can be found in numerous deposits laid down during the Tertiary and Quaternary Periods (65 million years ago to present). This is particularly evident along a number of beaches around our coastline.

The most recent part of it’s journey is via human activities; quarrying and extraction.

 

Flints reworked into beach deposits.
Chalk cliffs containing nodular flint bands.

So from a journey of over 70 million years ago in seas where mosasaurs once swam, to a designed driveway to keep your car on; flint has a story all of its own. You’ll never look at it in quite the same way again.

Jeff Stephenson

Designer to Design Director by James Smith

I’ve been working at Bowles & Wyer for 12 years now, that’s a long time I hear you say! Well yes, it certainly is but, to be honest it really hasn’t felt like it. I have been fortunate to work on some great projects during this time, honing my skills as a designer and project manager and working with some amazingly talented people along the way. I have had the freedom to enjoy my work, with my respected directors John Wyer and Chris Bowles, having given me enough rope to take chances, make mistakes and learn from them. Without this trust I would never have progressed into the position I find myself in as Design Director of Bowles & Wyer, a role I am very proud of. Trust without a doubt breeds motivation, creativity and success!

When I started out at Bowles & Wyer in 2005 the Iphone hadn’t even been introduced to the market and tablets were only of the medicinal kind! Edgar Davids (the chap with the odd specs) was playing for my beloved Tottenham Hotspur and the office was located in a cosy attic of a shared building in Berkhamsted. I remember my start date well, both nervous and excited, plus my eldest son Noah was born a couple of weeks after, making life even more interesting. He is now in his first year of secondary school and it’s scary how time moves on in the blink of an eye! I’ve had some ups and downs over the years as everyone does, I have been divorced and remarried in that time, and count myself very fortunate to have an amazingly supportive wife in Becky, and a young family of 5 fun loving and characterful children (Isla 15, Rosie 13, Noah 11, Isaac 11 and Finley 3) Life is never dull in our world and the fridge is never full for long!

Although many things have changed over the years, there are of course some reassuring constants, Bowles & Wyer is still a great place to work, we continue to take on and deliver the highest quality schemes, and the powerful 10am coffee can always be relied on to reset the pulse (brew for 4 minutes, no more, no less!) Plus John Wyer’s hair cut hasn’t changed one bit!

Now, I will be the first to admit, I never saw myself as a natural front man let alone Design Director, I haven’t always embraced the limelight over the years and I can be very quiet at times (the power of silence is a wonderful thing!). I am however fully aware that being introverted at times, means I can go unnoticed in a world and industry increasingly saturated by extroverts. My challenge to myself over the coming months and years is to work on this, raise my profile more in my own way and above all help to further promote Bowles & Wyer from the front foot. During my 12 years as a designer I have never stopped learning and listening, and never will, that’s the beauty of our profession. This has made me confident of holding my own against the best designers in our industry, I have just preferred to let my portfolio do the talking for me. The projects I am most proud of to date are The Lancasters (detailed design and project management), Eaton Square (concept to completion) A Surrey garden (BALI Grand Award winner) and more recently a Regents Park Garden (BALI Award Winner) and a large country garden in Cookham (recently finished). They all have different elements I am proud of but, above all they have felt like a real team effort to create and maintain.

A Regents Park Garden

Despite the varied and successful schemes we have worked on to date, I know there is so much more to come at Bowles & Wyer, and as Design Director, with a talented design team around me, I am convinced we will hit even greater highs over the coming years. So like my first day at the office, is it with nervous excitement that I look forward to the next chapter!

Eaton Square