TY - JOUR
T1 - The cretaceous-tertiary transition on the shallow Saharan platform of Southern Tunisia
AU - Keller, Gerta
AU - Adatte, Thierry
AU - Stinnesbeck, Wolfgang
AU - Stüben, Doris
AU - Kramar, Utz
AU - Berner, Zsolt
AU - Li, Liangquan
AU - Von Salis Perch-Nielsen, Katharina
N1 - Funding Information:
Acknowledgements - We are grateful to K.B. F611mi for his insights into phosphate sedimentation, to J. Richards for XRD, and M. Leosson for stable isotope sample preparations. This study was supported by grants from NSF OCE 9021338, NSF INT 95-04309, the Swiss National Fund grants No. 4943-1.96 and 4345-0.95 and dfg-grant N ° 128/4.L
PY - 1997
Y1 - 1997
N2 - A multidisciplinary approach to the study of a K/T boundary section on the Saharan Platform based on planktic and benthic foraminifera, calcareous nannofossils, lithology, stable isotopes, mineralogy and geochemistry reveals a biota stressed by fluctuating hyposaline, hypoxic littoral and nearshore environments, productivity changes, and a paleoclimate altering between seasonal warm to temperate and warm/humid conditions. Benthic foraminifera indicate that during the last 300 kyr of the Maastrichtian (CF1, Micula prinsii) deposition occurred in a inner neritic (littoral) environment that shallowed to a near-shore hyposaline and hypoxic environment during the last 100-200 kyr of the Maastrichtian. These conditions were accompanied by a seasonal warm to temperate climate that changed to warm/humid conditions with high rainfall, by decreasing surface productivity, and significantly decreasing planktic and benthic foraminiferal species richness. The K/T boundary is marked by an undulating erosional contact overlain by a 10 cm thick sandstone layer which is devoid of any exotic minerals or spherules. Their absence may be due to a short hiatus and the fact that the characteristic clay and red layer (zone P0) are missing. During the earliest Danian (Pla), low sea-levels prevailed with continued low oxygen, low salinity, high rainfall, high erosion and terrigenous sediment influx, accompanied by low diversity, low oxygen and low salinity tolerant species. These environmental conditions abruptly ended with erosion followed by deposition of a phosphatic siltstone layer that represents condensed sedimentation in an open (transgressive) marine environment. Above this layer, low sea-levels and a return to near-shore, hyposaline and hypoxic conditions prevailed for a short interval [(base of Plc(2)] and are followed by the re-establishment of normal open marine conditions (inner neritic) comparable to the late Maastrichtian. This marine transgression is accompanied by increased productivity, and the first diversified Danian foraminiferal assemblages after the K/T boundary event and represents the return to normal biotic marine conditions. Though the K/T Seldja section represents one of the most shallow marginal sea environments studied to date for this interval, it does not represent isolated or atypical conditions. This is suggested by the similar global trends observed in sea-level fluctuations, hiatuses, as well as faunal assemblages. We conclude that on the Saharan platform of southern Tunisia, longterm environmental stresses beginning 100-200 kyr before the K/T boundary and related to climate, sea-level, nutrient, oxygen and salinity fluctuations, were the primary causes for the eventual demise of the Cretaceous fauna in the early Danian. The K/T boundary bolide impact appears to have had a relatively incidental short-term effect on this marine biota.
AB - A multidisciplinary approach to the study of a K/T boundary section on the Saharan Platform based on planktic and benthic foraminifera, calcareous nannofossils, lithology, stable isotopes, mineralogy and geochemistry reveals a biota stressed by fluctuating hyposaline, hypoxic littoral and nearshore environments, productivity changes, and a paleoclimate altering between seasonal warm to temperate and warm/humid conditions. Benthic foraminifera indicate that during the last 300 kyr of the Maastrichtian (CF1, Micula prinsii) deposition occurred in a inner neritic (littoral) environment that shallowed to a near-shore hyposaline and hypoxic environment during the last 100-200 kyr of the Maastrichtian. These conditions were accompanied by a seasonal warm to temperate climate that changed to warm/humid conditions with high rainfall, by decreasing surface productivity, and significantly decreasing planktic and benthic foraminiferal species richness. The K/T boundary is marked by an undulating erosional contact overlain by a 10 cm thick sandstone layer which is devoid of any exotic minerals or spherules. Their absence may be due to a short hiatus and the fact that the characteristic clay and red layer (zone P0) are missing. During the earliest Danian (Pla), low sea-levels prevailed with continued low oxygen, low salinity, high rainfall, high erosion and terrigenous sediment influx, accompanied by low diversity, low oxygen and low salinity tolerant species. These environmental conditions abruptly ended with erosion followed by deposition of a phosphatic siltstone layer that represents condensed sedimentation in an open (transgressive) marine environment. Above this layer, low sea-levels and a return to near-shore, hyposaline and hypoxic conditions prevailed for a short interval [(base of Plc(2)] and are followed by the re-establishment of normal open marine conditions (inner neritic) comparable to the late Maastrichtian. This marine transgression is accompanied by increased productivity, and the first diversified Danian foraminiferal assemblages after the K/T boundary event and represents the return to normal biotic marine conditions. Though the K/T Seldja section represents one of the most shallow marginal sea environments studied to date for this interval, it does not represent isolated or atypical conditions. This is suggested by the similar global trends observed in sea-level fluctuations, hiatuses, as well as faunal assemblages. We conclude that on the Saharan platform of southern Tunisia, longterm environmental stresses beginning 100-200 kyr before the K/T boundary and related to climate, sea-level, nutrient, oxygen and salinity fluctuations, were the primary causes for the eventual demise of the Cretaceous fauna in the early Danian. The K/T boundary bolide impact appears to have had a relatively incidental short-term effect on this marine biota.
KW - K/T transition
KW - Paleoenvironment
KW - Saharan platform
UR - http://www.scopus.com/inward/record.url?scp=0031403474&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031403474&partnerID=8YFLogxK
U2 - 10.1016/S0016-6995(97)80218-5
DO - 10.1016/S0016-6995(97)80218-5
M3 - Article
AN - SCOPUS:0031403474
SN - 0016-6995
VL - 30
SP - 951
EP - 975
JO - Geobios
JF - Geobios
IS - 7
ER -