Editing Lower Jurassic rocks between Staithes and Port Mulgrave - an excursion

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=== Locality 1 [NZ 784 188] ===
 
=== Locality 1 [NZ 784 188] ===
  
Within the harbour, the Staithes Formation is well exposed in the cliff-foot ledges to the east. Note the cyclic development of the beds clearly defined by the sedimentary structures. Each unit has a sharp, erosive base, with shelly channel-floor lag deposits, overlain by sands showing planar and some hummocky '''cross-stratification''', with parallel and ripple lamination above. Increasing numbers of trace fossils progressively destroy the depositional fabric towards the finer-grained top of each unit. The sequence reflects the activity of intermittent, shallow-water storm events eroding the tops of previous cycles and depositing each unit under a waning current. The muddy bed tops were colonized by burrowing organisms, including bivalves such as ''Protocardia'', during the intervals between major storms. Fossils are common, including ''Protocardia truncata, Oxytoma inequivalvis'', the '''scaphopod''' ''Dentalium giganteum ''and belemnites. Ammonites are not common but evidence for the ''Prodactylioceras davoei ''and succeeding ''Amaltheus margaritatus '''''Biozones''' has been established within the formation.
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Within the harbour, the Staithes Formation is well exposed in the cliff-foot ledges to the east. Note the cyclic development of the beds clearly defined by the sedimentary structures. Each unit has a sharp, erosive base, with shelly channel-floor lag deposits, overlain by sands showing planar and some hummocky cross-stratification, with parallel and ripple lamination above. Increasing numbers of trace fossils progressively destroy the depositional fabric towards the finer-grained top of each unit. The sequence reflects the activity of intermittent, shallow-water storm events eroding the tops of previous cycles and depositing each unit under a waning current. The muddy bed tops were colonized by burrowing organisms, including bivalves such as ''Protocardia'',during the intervals between major storms. Fossils are common, including ''Protocardia truncata, Oxytoma inequivalvis'', the scaphopod ''Dentalium giganteum ''and belemnites. Ammonites are not common but evidence for the ''Prodactylioceras davoei ''and succeeding ''Amaltheus margaritatus ''Biozones has been established within the formation.
  
Cross the inner end of the east pier of the harbour, now fortified by large blocks of a Scandinavian '''gneiss''', onto the foreshore flats. In the cliff, the transition upwards into the shaley Cleveland Ironstone Formation can be seen. One-third of the distance to the headland, faulting is clear in the cliff, displacing the prominent ironstone bands near the top of the face. Bedding plane surfaces on the foreshore exibit excellent interference ripples at one point and many accumulations of fossils. As well as mixed assemblages, almost monospecific shell '''coquinas''' of ''Protocardia ''can be found, whilst elsewhere, this shallow-burrowing bivalve can be seen ''in situ ''in its burrow. Clusters of belemnite guards demonstrate current alignment. Fragments and even substantial trunks of wood may also be found. Clusters of fossils often act as loci for the formation of sideritic '''concretions''', giving the rock a dark, reddish-brown colour.
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Cross the inner end of the east pier of the harbour, now fortified by large blocks of a Scandinavian gneiss, onto the foreshore flats. In the cliff, the transition upwards into the shaley Cleveland Ironstone Formation can be seen. One-third of the distance to the headland, faulting is clear in the cliff, displacing the prominent ironstone bands near the top of the face. Bedding plane surfaces on the foreshore exibit excellent interference ripples at one point and many accumulations of fossils. As well as mixed assemblages, almost monospecific shell coquinas of ''Protocardia ''can be found, whilst elsewhere, this shallow-burrowing bivalve can be seen ''in situ ''in its burrow. Clusters of belemnite guards demonstrate current alignment. Fragments and even substantial trunks of wood may also be found. Clusters of fossils often act as loci for the formation of sideritic concretions, giving the rock a dark, reddish-brown colour.
  
 
=== Locality 2 [NZ 788 189] ===
 
=== Locality 2 [NZ 788 189] ===

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