Taddiford Gap Fossil Hunting

1844 – Early vertebrate finds reported
Searles Wood’s report introduced vertebrate material from the Hordle collections to the scientific record. Further descriptions soon established the importance of the locality’s mammals, fishes and reptiles.

1852 – Hastings documents the fossil-bearing cliffs
The Marchioness of Hastings developed a detailed account of the Hordle succession and its vertebrate remains, linking collections to the coastal beds.

1855 – Hastings collection enters the national museum
The British Museum acquired the Hastings collection, securing an important body of Hordle vertebrate material for continuing study.

1883 – A bed-by-bed coastal framework
Tawney and Keeping established numbered divisions of the Headon succession. Later revisions retain a recognisable bed framework, though not every subsequent author used identical numbering.

1921 – The charophyte flora studied
Reid and Groves investigated the fossil charophytes, adding freshwater vegetation evidence to the coastal record.

1925–1926 – A diverse fossil flora described
Marjorie Chandler’s work documented the fruit and seed flora, revealing the warm-climate vegetation represented in the Hordle deposits.

1961 – The fruit and seed flora revised
Chandler revised the earlier flora, refining the botanical identifications used to reconstruct the Eocene landscape.

1973 – Mammals resolved by fossil horizon
Cray’s revision distinguished the mammalian assemblages of the principal fossiliferous levels, improving the use of the coastal sequence in late Eocene biostratigraphy.

1973 – Rooted trees recorded in place
Fowler and colleagues documented in-situ conifer stumps, showing that part of the plant record represents rooted vegetation rather than only transported debris.

1979 – Aquatic roots preserved in three dimensions
Crane and Plint described permineralised aquatic roots, an unusual preservation mode providing anatomical evidence beyond compressed leaves and isolated seeds.

1997 – The coastal log refined
Detailed logging by Edwards and Daley provided the revised lithological succession used in the later vertebrate synthesis, preserving thin shell, plant and mammal-bearing intervals.

The Taddiford Gap–Hordle Cliff reach exposes the lower Headon Hill Formation, principally the Totland Bay Member. The following succession is a published composite of this continuous coastal reach, arranged from youngest to oldest. Thicknesses are those in that composite, not the height presently visible at Taddiford Gap. Historical bed numbers follow Tawney and Keeping as developed by Edwards and Daley; gaps in the published numbering are retained.

Quaternary cover and present exposure
River gravels truncate the Eocene strata at the cliff top. Slumps, talus and modern beach deposits repeatedly conceal or re-expose the older beds. These superficial deposits are separate from the Solent Group.

SOLENT GROUP

Headon Hill Formation

These Priabonian deposits record freshwater and brackish environments after the more fully marine Barton succession. Beds dip gently towards the south-east, approximately 2.5° in the published Hordle section. The eastern Colwell Bay Member and Milford Marine Bed belong to the Milford on Sea part of the coast and are not present at every Taddiford outcrop.

Totland Bay Member

Bed 33 (0.85 m)
Marl, grey-green, weathering rusty, with intercalated lenticular fine-grained sand.

Bed 32c (0.04 m)
Mud, carbonaceous, weathering pale pinky-grey; shell debris and bone fragments (Rodent bed in part).

Bed 32b (0.10 m)
Marl, sandy, pale-green; abundant shell debris and bone fragments; Lymnaea, theridomyid teeth (Limnaea marl, Rodent bed in part).

Bed 32a (0.20 m)
Marl, sandy, pale-green to rusty, to marly sand; scattered shell fragments.

Bed 31c (0.60 m)
Sand, fine-grained.

Bed 31b (0.80–1.07 m)
Muddy silt, thin bedded, passing up into fine-grained sand.

Bed 31a (0.40–0.46 m)
Muddy silt, thin bedded with marl and thin black mud intercalations; lenses of Viviparus lentus, Potamaclis turritissima, Unio solandri, ostracods; bands of seeds at base (Limnocarpus band).

Bed 30b (2.80 m)
Greyish marls and clays, with intercalated fine-grained sand beds.

Bed 30a (c. 2.50 m)
Muds, thin bedded, with intercalated fine-grained sand, especially near base, with U. solandri, V. lentus, seeds of Stratiotes, charophytes.

Bed 29 (0.50 m)
Muds; seam of fine-grained sand with P. turritissima, basal sand resting on strongly burrowed junction.

Bed 28 (0.50 m)
Sand, fine-grained, pale-brown to purplish; black muds with sand-filled burrows; humic muds at base (Chara bed).

Bed 26 (0.25–1.12+ m)
Marl with sand-filled burrows passing down into sandy limestone.

Bed 25 (0.58 m)
Sand, medium-fine grained; thin marl near top.

Bed 24 (0.75 m)
Marl, with calcareous mottles.

Bed 23 (0.53 m)
Sand, fine-grained, passing up into muddy silt; black mud lenses in upper part.

Bed 22 (0.36 m)
Mud, silty, blue; carbonate mottles common.

Bed 21 (0.25 m)
Mud, shelly fine-grained sand layers; Potamomya plana.

Bed 20 (0.28 m)
Sand, very fine-grained, passing up into mud with carbonate mottles; black mud lenses in upper part.

Bed 19/18 (0.40 m)
Mud, blue carbonate mottles at top; shelly layers; P. plana, Lymnaea at base.

Bed 17 (0.10 m)
Limestone; Lymnaea, Australorbis (Lymnaean limestone).

Bed 16 (0.95 m)
Mud, greenish; thin black mud at top, rusty-weathering mudstone; nodules towards base.

Bed 15c (0.10–0.20 m)
Silt, muddy; P. plana.

Bed 15b (1.36 m)
Sand, very fine-grained or silt; greenish mud bands; calcareous cementation near top; shell bed at base with P. plana (Crocodile bed).

Bed 15a (0.32 m)
Thin bedded muddy silt and silty mud, brown and black; P. plana and seeds.

Bed 14 (0.04 m)
Mud, silty; sand-filled burrows.

Bed 13 (0.20–0.70 m)
Sand, medium-grained; shell debris at base (Rolled Bone Bed).

Bed 12 (0.50–1.90 m)
Muds, mainly very dark-grey, interbedded with layers and lenses of grey medium-grained sand; and sand, medium-grained; lignite layers; plant debris and seeds.

Bed 11 (1.30 m)
Sand, medium-grained.

Bed 10 (0.40 m)
Mud, silty: in-situ carbonaceous woody roots (Leaf bed).

Bed 9 (2.50 m)
Mud, blue-green, passing down into sand, fine, bluish mud mottles; muddy silt towards base; V. lentus, bones (Mammal bed).

Bed 8 (1.00 m)
Mud, massive, grey-blue; large rusty-weathering calcareous mudstone nodules near base.

Bed 6 (0.15 m)
Silt or very fine sand, mottled with blue mud.

Bed 5 (1.70 m)
Mud, massive, grey-blue, brown mottles, silty near base.

Bed 1–4 (1.25 m)
Alternations of black and grey muds, some silty or sandy; some levels with rootlets and burrows; P. plana, Corbicula deperdita.

Fossil-bearing horizons and lateral change
The Mammal Bed includes bone-bearing pale sands and blue-green sandy clays; fossils can be partly associated. The Crocodile Bed contains local rich pockets, rather than evenly distributed skeletons, and also yields turtles and other vertebrates. The Rodent Bed is a restricted, higher horizon with small, fragmented, water-sorted remains. These differences matter when interpreting an isolated find. The fossil flora includes both aquatic accumulations and the more diverse Leaf-and-Seed Bed, with rooted conifer stumps recorded in place. Lignite-rich palaeochannel sediment near Beacon Cliff is a lateral channel feature, not another uniform layer to add to this log.

BARTON GROUP

Becton Sand Formation

The sand-dominated marine to marginal-marine succession underlies the Headon Hill Formation. The basal lignitic beds historically labelled L belong with the Headon Hill succession in the modern hierarchy. The wider Becton succession is described in the Beckton Bunny guide; its regional maximum thickness and inland boreholes are not measurements at this gap.

References

Benton, Cook & Hooker (2005), Hordle Cliff, GCR 32, Table 3.2
Benton & Spencer (1995), Hordle Cliff, GCR 10
Cleal et al. (2001), Hordle–Beacon Cliffs, GCR 22
Daley & Balson (1999), British Tertiary Stratigraphy, GCR 15, Barton Cliffs and Studley Wood
BGS Lexicon: Headon Hill Formation