Sedimentation rates of planktonic and benthic foraminifera in sediment from the Atlantic continental margin of Portugal and Morocco

• Main Author: Thiede, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Bornträger 1973
• Subjects: Planktonic foraminifera
• Online Access: https://oceanrep.geomar.de/id/eprint/56618/; https://oceanrep.geomar.de/id/eprint/56618/1/Thiede_J_1973_C.pdf

Cores from the Atlantic Ibero-Moroccan continental rise and slope contain fine-grained Late Pleistocene and Holocene sediments. These young sediments cover the continental margin in large lensformed litho- and biostratigraphically well-defined units. The total sedimentation rates range from 4 cm/1000 yrs. to 27 cm/1000 yrs. off Portugal and from 6 cm/1000 yrs. to 14 cm/1000 yrs. off Morocco. Only a small proportion of these sediments usually consists of sand-sized particles (> 0.063 mm) which are mostly dominated by foraminifera. Both planktonic and benthic foraminifera are much more abundant in Late Pleistocene and Holocene samples from the upper slope in comparison to those from the deeper slope and from the abyssal plains. Total sedimentation rates during cool and warm climatic stages are rather similar for both groups of foraminifera. For example, in Late Holocene sediments 7 X 103 benthic and 201 X 103 planktonic foraminifera (fraction 0.63-0.20 mm) per 100 cm 2 and 1000 yrs. are preserved in the Tagus, 10-19 x 103 benthic and about 1.3 X 106 planktonic foraminifera are preserved in the Seine abyssal plain sediments. Values from the upper slope sediments are higher for benthic foraminifera by a factor of 60 off Portugal and 60 to 70 off Morocco. The values for planktonic ones differ by factots of 6-12 and 6 respectively. These numbers seem to reflect differences in production and preservation. Production rates of planktonic foraminifera generally seem to be somewhat higher during Holocene than during Late Pleistocene, and the rates of benthic foraminifera appear rather higher during Late Pleistocene than during Holocene.