TY - JOUR
T1 - Impacts of flamingos on saline lake margin and shallow lacustrine sediments in the Kenya Rift Valley
AU - Scott, Jennifer J.
AU - Renaut, Robin W.
AU - OWEN, R Bernhart
N1 - Funding Information:
This research was conducted under permits issued from the Ministry of Education, Science and Technology, Republic of Kenya . Sincere thanks are extended to Gail Ashley (Rutgers University), Steve Driese (Baylor University), and Jenna Cole (Western Kentucky University) for assistance in the field and discussions that contributed to this work. Encouraging discussions with Leroy Leggitt (Loma Linda University) are very much appreciated. We also thankWilliam Kimosop (Chief Warden, North Kenya Rift) for continued support of our research. Funding was provided by the Natural Sciences and Engineering Research Council of Canada (Research Grant 629–08 to R.W.R., a PGS D scholarship to J.J.S., a PDF grant to J.J.S., and Hong Kong Research Grants Council (GRF201709) and Hong Kong Baptist University (FRG/08-09/II-25) grants to R.B.O. We gratefully acknowledge the work of Blaine Novakovski (University of Saskatchewan), Diane Caird (University of Alberta), and David Pirie (University of Alberta) who completed the XRD analyses and prepared thin sections. We very much appreciate the conscientious reviews by Ricardo Melchor and an anonymous reviewer, which helped to improve an earlier draft.
PY - 2012/11/15
Y1 - 2012/11/15
N2 - Studies of modern, Holocene, and Pleistocene sediments around saline to hypersaline, alkaline Lake Bogoria and Lake Magadi show that evidence of flamingo activity in marginal areas of these lakes is nearly ubiquitous. Flamingos produce discrete structures such as webbed footprints (~ 9 cm long, ~ 11 cm wide) and nest mounds (~ 30. cm wide, ~ 20. cm high), and they also extensively rework sediments in delta front, delta plain, and shoreline areas. Large (~ 0.5-2. cm in diameter), pinched, 'bubble pores' and ped-like mud clumps are formed by the trampling and churning of wet clay-rich sediments in these settings. Flamingo nest mounds, although superficially similar to some thrombolite mounds, are typically internally structureless, unless formed on pre-existing sediments that preserve internal structures. The flamingo mounds consist of a dense, packed oval-shaped core, a surrounding 'body' of packed sediment, and an external layer with a ped-like texture of clumped mud. The nests may contain open holes from roots or feather shafts incorporated into the nest, and (or) burrows produced once the nests are abandoned. In areas with high densities of flamingos, lake margin sediments may be preferentially compacted, particularly at breeding sites, and become resistant to subaerial erosion and the effects of transgressive ravinement on time scales ranging from seasons to tens of thousands of years. The relatively well-compacted nest mounds and associated sediments also contribute to the stability of delta distributary channels during regressive-transgressive cycles, and can lead to the minor channelization of unconfined flows where currents are diverted around nest mounds. Pleistocene exhumed surfaces of relatively well-indurated lake margin sediments at Lake Bogoria and Lake Magadi that are interpreted as combined regressive and transgressive surfaces (flooding surface/sequence boundary) preserve evidence of flamingo activities, and are overlain by younger, porous lacustrine silts that preserve large bubble pores produced by flamingos.
AB - Studies of modern, Holocene, and Pleistocene sediments around saline to hypersaline, alkaline Lake Bogoria and Lake Magadi show that evidence of flamingo activity in marginal areas of these lakes is nearly ubiquitous. Flamingos produce discrete structures such as webbed footprints (~ 9 cm long, ~ 11 cm wide) and nest mounds (~ 30. cm wide, ~ 20. cm high), and they also extensively rework sediments in delta front, delta plain, and shoreline areas. Large (~ 0.5-2. cm in diameter), pinched, 'bubble pores' and ped-like mud clumps are formed by the trampling and churning of wet clay-rich sediments in these settings. Flamingo nest mounds, although superficially similar to some thrombolite mounds, are typically internally structureless, unless formed on pre-existing sediments that preserve internal structures. The flamingo mounds consist of a dense, packed oval-shaped core, a surrounding 'body' of packed sediment, and an external layer with a ped-like texture of clumped mud. The nests may contain open holes from roots or feather shafts incorporated into the nest, and (or) burrows produced once the nests are abandoned. In areas with high densities of flamingos, lake margin sediments may be preferentially compacted, particularly at breeding sites, and become resistant to subaerial erosion and the effects of transgressive ravinement on time scales ranging from seasons to tens of thousands of years. The relatively well-compacted nest mounds and associated sediments also contribute to the stability of delta distributary channels during regressive-transgressive cycles, and can lead to the minor channelization of unconfined flows where currents are diverted around nest mounds. Pleistocene exhumed surfaces of relatively well-indurated lake margin sediments at Lake Bogoria and Lake Magadi that are interpreted as combined regressive and transgressive surfaces (flooding surface/sequence boundary) preserve evidence of flamingo activities, and are overlain by younger, porous lacustrine silts that preserve large bubble pores produced by flamingos.
KW - Biogenic structures
KW - Bioturbation
KW - East African lakes
KW - Flamingo
KW - Mud mounds
KW - Thrombolite
UR - http://www.scopus.com/inward/record.url?scp=84865744511&partnerID=8YFLogxK
U2 - 10.1016/j.sedgeo.2012.07.007
DO - 10.1016/j.sedgeo.2012.07.007
M3 - Journal article
AN - SCOPUS:84865744511
SN - 0037-0738
VL - 277-278
SP - 32
EP - 51
JO - Sedimentary Geology
JF - Sedimentary Geology
ER -