TY - JOUR

T1 - Faunal succession in the upper Cambrian (Furongian) Leptoplastus Superzone at Slemmestad, southern Norway

AU - Rasmussen, Bo Wilhelm

AU - Nielsen, Arne Thorshøj

AU - Schovsbo, Niels H.

PY - 2015

Y1 - 2015

N2 - The ‘Middle’ Cambrian–Tremadocian Alum Shale Formation is generally strongly tectonised in the Oslo area (southern Norway) and, as such, nocomplete succession through the Furongian exists in the area. The present paper presents a restored part of the Furongian interval through theLeptoplastus Superzone that has been measured and sampled at Slemmestad harbour. The limestone layers and nodule levels within the shale arepreserved in the correct stratigraphic order with only limited repetition due to thrusting. Here the Leptoplastus Superzone is about 3.1 m thick.WithinScandinavia the superzone has previously been subdivided into the Leptoplastus paucisegmentatus, L. raphidophorus, L. crassicornis, L.ovatus, L. angustatus and L. stenotus zones, of which the L. paucisegmentatus Zone has not been recorded in the Oslo area. It may be truly absentor the interval may be devoid of fossiliferous limestone. It is alternatively possible that the index fossil is absent for ecological reasons. Variable firstappearances of key taxa have somewhat confused the subdivision of the Leptoplastus Superzone. The order of appearance of L. ovatus, L. crassicornisand L. angustatus thus differs between Slemmestad and Andrarum in southern Sweden, and consequently the L. ovatus Zone is herein proposedabandoned as L. ovatus co-occurs with L. crassicornis. The L. angustatus Zone has also been proposed abandoned by recent authors. Based ondetailed biostratigraphical data from Slemmestad and Andrarum, a combined L. crassicornis–L. angustatus Zone is defined; the lower boundary ischaracterised by the first appearance of L. crassicornis. The present study furthermore shows that Protopeltura holtedahli occurs in the Parabolinaspinulosa Zone and that Protopeltura broeggeri is restricted to the upper part of the new Leptoplastus crassicornis–L. angustatus Zone. TheseProtopeltura species do not characterise separate zones or subzones as previously proposed. A lectotype of Ctenopyge neglecta var. bornholmensisPoulsen, 1923, now Leptoplastus bornholmensis, is designated and reillustrated.

AB - The ‘Middle’ Cambrian–Tremadocian Alum Shale Formation is generally strongly tectonised in the Oslo area (southern Norway) and, as such, nocomplete succession through the Furongian exists in the area. The present paper presents a restored part of the Furongian interval through theLeptoplastus Superzone that has been measured and sampled at Slemmestad harbour. The limestone layers and nodule levels within the shale arepreserved in the correct stratigraphic order with only limited repetition due to thrusting. Here the Leptoplastus Superzone is about 3.1 m thick.WithinScandinavia the superzone has previously been subdivided into the Leptoplastus paucisegmentatus, L. raphidophorus, L. crassicornis, L.ovatus, L. angustatus and L. stenotus zones, of which the L. paucisegmentatus Zone has not been recorded in the Oslo area. It may be truly absentor the interval may be devoid of fossiliferous limestone. It is alternatively possible that the index fossil is absent for ecological reasons. Variable firstappearances of key taxa have somewhat confused the subdivision of the Leptoplastus Superzone. The order of appearance of L. ovatus, L. crassicornisand L. angustatus thus differs between Slemmestad and Andrarum in southern Sweden, and consequently the L. ovatus Zone is herein proposedabandoned as L. ovatus co-occurs with L. crassicornis. The L. angustatus Zone has also been proposed abandoned by recent authors. Based ondetailed biostratigraphical data from Slemmestad and Andrarum, a combined L. crassicornis–L. angustatus Zone is defined; the lower boundary ischaracterised by the first appearance of L. crassicornis. The present study furthermore shows that Protopeltura holtedahli occurs in the Parabolinaspinulosa Zone and that Protopeltura broeggeri is restricted to the upper part of the new Leptoplastus crassicornis–L. angustatus Zone. TheseProtopeltura species do not characterise separate zones or subzones as previously proposed. A lectotype of Ctenopyge neglecta var. bornholmensisPoulsen, 1923, now Leptoplastus bornholmensis, is designated and reillustrated.

KW - Faculty of Science

KW - Cambrian

KW - Furongian

KW - Alum Shale

KW - biostratigraphy

KW - trilobites

KW - Norway

KW - Scandinavia

KW - Leptoplastus Superzone

U2 - 10.17850/njg95-1-01

DO - 10.17850/njg95-1-01

M3 - Journal article

VL - 95

SP - 1

EP - 22

JO - Norsk Geologisk Tiddsskrift

JF - Norsk Geologisk Tiddsskrift

SN - 0029-196X

IS - 1

ER -