A recent 'Odd Layer' at The Naze - 16 Sep 2025 скачать в хорошем качестве

A recent 'Odd Layer' at The Naze - 16 Sep 2025

Understanding the Mysterious Gravel Layer at The Naze If you have recently walked the eroding cliffs at Walton-on-the-Naze in Essex, you might spot a band of sand and gravel pebbles sitting a couple of feet below the surface of the dark, sticky London Clay. This odd layer looks embedded in the clay but is not part of the original formation. The London Clay is ancient, about 50 million years old from the Eocene epoch, when the area was a muddy sea floor. Because the Naze cliffs are retreating steadily under wave attack, this gravel pocket has probably been revealed only recently. Each winter storm can undercut several feet of cliff, so features appear for a short time before collapsing or washing away. It is a fleeting window into deep time. Following a recent visit, I have put together some ideas about how this gravel might have formed. These are my own observations based on fieldwork, old studies, and local guides. How the Layer Might Have Formed This is not a flat, continuous layer. It seems more like pockets of gravel that filled depressions or hollows near the top of the London Clay. Over millions of years, seas advanced and retreated, rivers changed course, and ice ages came and went. These forces could have eroded the clay, created dips, deposited gravel, and then covered it, making it appear buried today. The gravel may come from one or both of two main time periods: Late Pliocene, about 3.3 to 2.5 million years ago: The Red Crag sea flooded the area. A shallow, stormy sea could have reworked older pebbles from rivers like an early Thames and dropped them into hollows. The gravel might include well-rounded flints, shell fragments, shark teeth, or black phosphatic nodules. Pleistocene, about 2.5 million years ago to 11,700 years ago: During ice ages and warmer spells, rivers like the ancestral Thames, called the Kesgrave Thames, or glacial meltwater could have carried pebbles from far away, for example quartz from the Midlands. These may have filled or refilled hollows. Periglacial processes could have added angular pebbles or mixed in clay bits. After filling, the hollows may have been sealed by slumped clay, wind-blown loess (brickearth), or other deposits. Erosion of surrounding material could leave these pockets looking like they are inside the clay, especially as the cliffs wear away today particularly at the northern end of The Naze. Where the Possibilities Overlap The gravel could be a mix of these eras, with erosion playing a key role in exposing or preserving it. Its shallow position just below the top fits either timeline. Clues to look for include pebble types or nearby features such as folded clay or ice-wedge cracks from frozen ground. Different Ways the Hollows Might Have Formed Diapirism, squeezing from below: the London Clay can behave like soft toothpaste under pressure, forming bulges or hollows. In the Pliocene, natural underground movements could have created initial depressions. In the Pleistocene, extra weight from glaciers or ice sheets might have reopened or formed new hollows. Gravel could then settle in, capped by slumped clay or loess, and might show signs of glacial influence such as ice-wedge marks. This could explain why the gravel appears to sit within the clay. Erosional scours, carving from above. Alternatively, the top of the London Clay may have been shaped by repeated scouring: Pliocene marine currents from the Red Crag sea could have gouged channels or pockets. Pleistocene rivers or glacial and periglacial flows may have dug deeper, leaving fluvial gravels in concave-up hollows. The gravel infills these cuts, and after overlying material erodes away, isolated pockets remain under a thin loess cap. This is not a true layer inside but an illusion from the irregular surface. Marine gravel could include shells or bored pebbles; river deposits might have quartz mixes or cross-bedded sands; periglacial deposits could be angular, poorly sorted pebbles with wavy edges. These mechanisms are not mutually exclusive. Diapirism could create initial hollows, then erosion deepen them. Glacial loading could have enhanced either process. Summary What it might be: Gravel pockets in London Clay hollows, possibly from Pliocene seas, Red Crag, and/or Pleistocene rivers and glacial episodes, Kesgrave Thames and Anglian ice age. How it might have formed: Filled depressions created by clay diapirism or erosional scours, then capped by dust or slumped material, possibly a mix of both mechanisms. Why you are seeing it now: The Naze cliffs are eroding rapidly. This gravel band is almost certainly a temporary exposure, revealed only because the sea keeps eating into the cliff face. Why it is interesting: A snapshot of Essex's restless past, shifting seas, rivers, and ice ages. On a visit, it is possible to see clues that suggest marine, river, or periglacial origins, but the exact story is open to interpretation.