Benthic macrofauna variations and community structure in Cenomanian cyclic chalk-marl from Southerham Grey Pit, SE England

TY - JOUR

T1 - Benthic macrofauna variations and community structure in Cenomanian cyclic chalk-marl from Southerham Grey Pit, SE England

AU - Lauridsen, Bodil Wesenberg

AU - Gale, A. S.

AU - Surlyk, Finn

PY - 2009

Y1 - 2009

N2 - Cenomanian chalk-marl couplets from England represent the 20 ka Milankovitch precession cycle. Fossil communities from both chalk and marl are identified to test if the orbital fluctuations and the associated changes in substrate lithology and climate exerted any control on the benthic macrofauna. The material comprises washing residues of 24 bulk samples collected from chalk and marl half-cycles. A total of 5055 invertebrate specimens were retrieved and referred to 68 species, forming the basis for the recognition of six guilds. In general, the fauna is more diverse in marl than in chalk, but it is remarkable and somewhat surprising that the guild assemblages of marl and chalk show no difference. Thus the substrate character of the two lithologies did not exert any influence on the modes of life of the benthic fauna in spite of a difference in clay content of about 20%. The fauna was clearly well adapted to both facies and thus to the fine grain size of the substrate rather than to lithology. The systematic difference in diversity between chalk and marl samples was possibly caused by long-term climatic and oceanographic changes and thus could represent a biological response to Milankovitch cyclicity.

AB - Cenomanian chalk-marl couplets from England represent the 20 ka Milankovitch precession cycle. Fossil communities from both chalk and marl are identified to test if the orbital fluctuations and the associated changes in substrate lithology and climate exerted any control on the benthic macrofauna. The material comprises washing residues of 24 bulk samples collected from chalk and marl half-cycles. A total of 5055 invertebrate specimens were retrieved and referred to 68 species, forming the basis for the recognition of six guilds. In general, the fauna is more diverse in marl than in chalk, but it is remarkable and somewhat surprising that the guild assemblages of marl and chalk show no difference. Thus the substrate character of the two lithologies did not exert any influence on the modes of life of the benthic fauna in spite of a difference in clay content of about 20%. The fauna was clearly well adapted to both facies and thus to the fine grain size of the substrate rather than to lithology. The systematic difference in diversity between chalk and marl samples was possibly caused by long-term climatic and oceanographic changes and thus could represent a biological response to Milankovitch cyclicity.

U2 - 10.1144/0016-76492007-164

DO - 10.1144/0016-76492007-164

M3 - Journal article

SN - 0016-7649

VL - 166

SP - 115

EP - 127

JO - Journal of the Geological Society - London

JF - Journal of the Geological Society - London

ER -