Editing Lower and Middle Jurassic rocks between Robin Hood's Bay and Hawsker Bottoms - an excursion

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=== Locality 10, Clock Case Nab [NZ 956 071] ===
 
=== Locality 10, Clock Case Nab [NZ 956 071] ===
  
A thin split ironstone nodule horizon can be seen at the base of Clock Case Nab. Looking northwest across the embayment called Far Jetticks towards Hawsker High Cliff and High Scar, there is a fine view of the upper Middle Lias (''spinatum ''Biozone) on the foreshore section with a thick sequence of the Upper Lias (Whitby Mudstone Formation: Grey Shale Member to Alum Shale Member) in the cliff section above.
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A thin split ironstone nodule horizon can be seen at the base of Clock Case Nab. Looking northwest across the embayment called Far Jetticks towards Hawsker High Cliff and High Scar, there is a fine view of the upper Middle Lias ''(spinatum ''Biozone) on the foreshore section with a thick sequence of the Upper Lias (Whitby Mudstone Formation: Grey Shale Member to Alum Shale Member) in the cliff section above.
  
 
=== Locality 11, Far Jetticks [NZ 953 073] ===
 
=== Locality 11, Far Jetticks [NZ 953 073] ===
  
The Upper Middle Lias section at Far Jetticks, some 12.5 m thick, may be compared with that seen in the Staithes–Port Mulgrave section (Excursion 16). All the subzone index ammonites may be found on this section together with many belemnites, bivalves and nests of ''Tetrarhynchia''.
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The Upper Middle Lias section at Far Jetticks, some 12.5 m thick, may be compared with that seen in the Staithes–Port Mulgrave section (Excursion 16). All the subzone index ammonites may be found on this section together with many belemnites, bivalves and nests of ''Tetrarhynchia''.
  
 
While in the vicinity of Hawsker High Cliff look ''(with extreme caution) ''at the fallen material at the base of the cliff. Pyrite-skinned nodules contain ''Harpoceras exaratum'' and ''H. falciferum'' (index fossils of the Mulgrave Shale Member), while grey nodules containing ''Dactylioceras'' and ''Hildoceras'' indicate the Grey Shale and Alum Shale Members.
 
While in the vicinity of Hawsker High Cliff look ''(with extreme caution) ''at the fallen material at the base of the cliff. Pyrite-skinned nodules contain ''Harpoceras exaratum'' and ''H. falciferum'' (index fossils of the Mulgrave Shale Member), while grey nodules containing ''Dactylioceras'' and ''Hildoceras'' indicate the Grey Shale and Alum Shale Members.
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=== Locality 12, Hawsker High Scar [NZ 951 077] ===
 
=== Locality 12, Hawsker High Scar [NZ 951 077] ===
  
The calcareous sandstone that forms the top of the scar, which may involve a 3 m scramble, is some 3.20 m below the top of the Middle Lias. The sediments here indicate an important event boundary within the Yorkshire Basin, where the shallow-water sediments of the Cleveland Ironstone Formation abruptly change to deeper-water sediments of the Whitby Mudstone Formation (Grey Shale Member).
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The calcareous sandstone that forms the top of the scar, which may involve a 3 m scramble, is some 3.20 m below the top of the Middle Lias. The sediments here indicate an important event boundary within the Yorkshire Basin, where the shallow-water sediments of the Cleveland Ironstone Formation abruptly change to deeper-water sediments of the Whitby Mudstone Formation (Grey Shale Member).
  
 
=== Locality 13, White Stone Hole (NZ 950 076] ===
 
=== Locality 13, White Stone Hole (NZ 950 076] ===
  
The Grey Shale Member is reasonably well exposed here near the base of the subcliff. The Mulgrave Shale Member is well exposed 200 m to the northwest, where the continuous concretion horizon of the Top Jet Dogger and the Whale Stone concretions some 2 m below can be seen at the base of the subcliff (the productive jet horizon on the Yorkshire coast is between these two concretion bands).
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The Grey Shale Member is reasonably well exposed here near the base of the subcliff. The Mulgrave Shale Member is well exposed 200 m to the northwest, where the continuous concretion horizon of the Top Jet Dogger and the Whale Stone concretions some 2 m below can be seen at the base of the subcliff (the productive jet horizon on the Yorkshire coast is between these two concretion bands).
  
At this point the beach section becomes less clear as it is littered with deltaic sandstone blocks from the cliff above. From White Horse [NZ 949 078] onwards the foreshore section is largely obscured by large landslips. At the top of this landslip complex is a path of sorts (it continually changes owing to movement) which should be followed to Pursglove Stye [NZ 945 082]. At Pursglove Stye, the remains of the steep path up the cliff (now disrupted by landslip) may be seen sometimes marked by a fixed rope (NB — test the rope before relying on it). Ascend the steep Heather covered Alum Shales slope carefully, picking you route with care until you reach the base of the vertical Middle Jurassic sandstone cliff at Location 14 [NZ 946 081], where you will meet the coastal cliff-top path.
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At this point the beach section becomes less clear as it is littered with deltaic sandstone blocks from the cliff above. From White Horse [NZ 949 078] onwards the foreshore section is largely obscured by large landslips. At the top of this landslip complex is a path of sorts (it continually changes owing to movement) which should be followed to Pursglove Stye [NZ 945 082]
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At Pursglove Stye, the remains of the steep path up the cliff (now disrupted by landslip) may be seen sometimes marked by a fixed rope (NB — test the rope before relying on it). Ascend the steep Heather covered Alum Shales slope carefully, picking you route with care until you reach the base of the vertical Middle Jurassic sandstone cliff at Location 14 [NZ 946 081], where you will meet the coastal cliff-top path.
  
 
=== Locality 14 [NZ 946 081] ===
 
=== Locality 14 [NZ 946 081] ===
  
Before finally getting to the top of the cliffs at Hawsker Bottoms, an interesting minor detour involves walking southeast for 0.1 km at the base of the vertical Middle Jurassic sandstone cliff. The sections in the Saltwick Formation are particularly good with excellent channel features, but at the end of this path is also an excellent exposure of the ferruginous sandstones of the Dogger Formation (Aalenian, Middle Jurassic). This marine sandstone contains sporadic bivalves and often has a remainie bed at the base consisting of phosphatic pebbles and ammonite fragments eroded from the Upper Lias beneath. There is a stratigraphical hiatus at the junction of the Lias with the Dogger.
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Before finally getting to the top of the cliffs at Hawsker Bottoms, an interesting minor detour involves walking southeast for 0.1 km at the base of the vertical Middle Jurassic sandstone cliff. The sections in the Saltwick Formation are particularly good with excellent channel features, but at the end of this path is also an excellent exposure of the ferruginous sandstones of the Dogger Formation (Aalenian, Middle Jurassic). This marine sandstone contains sporadic bivalves and often has a remainie bed at the base consisting of phosphatic pebbles and ammonite fragments eroded from the Upper Lias beneath. There is a stratigraphical hiatus at the junction of the Lias with the Dogger.
  
On reaching the cliff-top footpath, walk back to Robin Hood's Bay and the car park, stopping, '''and with care''', looking at the Jet Rock workings (with rare jet planks) at the top of Clock Case Nab [NZ 954 070].
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On reaching the cliff-top footpath, walk back to Robin Hood's Bay and the car park, stopping, and with care, looking at the Jet Rock workings (with rare jet planks) at the top of Clock Case Nab [NZ 954 070].
  
 
== [[Yorkshire rocks and landscape: a field guide#Glossary|Glossary]] ==
 
== [[Yorkshire rocks and landscape: a field guide#Glossary|Glossary]] ==
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[[Category:Yorkshire rocks and landscape: a field guide ]]
 
 
[[Category:9. Eastern England from the Tees to the Wash]]
 
[[Category:9. Eastern England from the Tees to the Wash]]

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