Carbonate deposition began about 770 ka ago in a relatively deep-water slope environment and is r... more Carbonate deposition began about 770 ka ago in a relatively deep-water slope environment and is represented by a series of debris flows. Lithoclasts within these rocks, indicate that older limestones already existed in the area. Subsequent accretion involved the downslope ...
Deep Sea Research Part A. Oceanographic Research Papers, 1989
... Distributional pattern of planktonic foraminifers and pteropods in surface waters and top cor... more ... Distributional pattern of planktonic foraminifers and pteropods in surface waters and top core sediments of the Red Sea, and adjacent areas controlled by the monsoonal regime and other ecological factors ANABELLE AURAS-SCHUDNAGIES,*t DICK KROON,:~ GERALD ...
... Here, we present a Holocene stable O-isotope record from the summer-dwelling planktic foramin... more ... Here, we present a Holocene stable O-isotope record from the summer-dwelling planktic foraminifer G. bulloides in Core 905 off Somalia. ... The nucleus for the present work is a high-resolution study on Core 905 from the Arabian Sea off Somalia. Fig. 3 and Fig. ...
Two sediment cores from the Zaire Fan and the Angola Margin have been investigated for their comp... more Two sediment cores from the Zaire Fan and the Angola Margin have been investigated for their composition of terrigenous and biogenic constituents, respectively. For the late Quaternary, kaolinite/feldspar ratios and variations of terrigenous element ratios of Zr, Ti, K, Rb, and Al reveal that the composition of Zaire River sediment load has fluctuated in tune with precessional variations of boreal
1] Water column stratification increased at climatic transitions from cold to warm periods during... more 1] Water column stratification increased at climatic transitions from cold to warm periods during the late Quaternary and led to anoxic conditions and sapropel formation in the deep eastern Mediterranean basins. Highresolution data sets on sea-surface temperatures (SST) (estimated from U 37 k 0 indices) and d 18 O of planktonic foraminifer calcite (d 18 O fc ) across late Pleistocene sapropel intervals show that d 18 O fc decreased (between 1 and 4.6%) and SST increased (between 0.7°and 6.7°C). Maximal d 18 O seawater depletion of eastern Mediterranean surface waters at the transition is between 0.5 and 3.0%, and in all but one case exceeded the depletion seen in a western Mediterranean core. The depletion in d 18 O seawater is most pronounced at sapropel bases, in agreement with an initial sudden input of monsoon-derived freshwater. Most sapropels coincide with warming trends of SST. The density decrease by initial freshwater input and continued warming of the sea surface pooled fresh water in the surface layer and prohibited deep convection down to ageing deep water emplaced during cold and arid glacial conditions. An exception to this pattern is ''glacial'' sapropel S6; its largest d 18 O seawater depletion (3%) is almost matched by the depletion in the western Mediterranean Sea, and it is accompanied by surface water cooling following an initially rapid warming phase. A second period of significant isotopic depletion is in isotope stage 6 at the 150 kyr insolation maximum. While not expressed as a sapropel due to cold SST, it is in accord with a strengthened monsoon in the southern catchment.
Knowledge about dietary niche is key to understanding hominin evolution, since diet influences bo... more Knowledge about dietary niche is key to understanding hominin evolution, since diet influences body proportions, brain size, cognition, and habitat preference. In this study we provide ecological context for the current debate on modernity (or not) of aquatic resource exploitation by hominins. We use the Homo erectus site of Trinil as a case study to investigate how research questions on possible dietary relevance of aquatic environments can be addressed. Faunal and geochemical analysis of aquatic fossils from Trinil Hauptknochenschicht (HK) fauna demonstrate that Trinil at w1.5 Ma contained near-coastal rivers, lakes, swamp forests, lagoons, and marshes with minor marine influence, laterally grading into grasslands. Trinil HK environments yielded at least eleven edible mollusc species and four edible fish species that could be procured with no or minimal technology. We demonstrate that, from an ecological point of view, the default assumption should be that omnivorous hominins in coastal habitats with catchable aquatic fauna could have consumed aquatic resources. The hypothesis of aquatic exploitation can be tested with taphonomic analysis of aquatic fossils associated with hominin fossils. We show that midden-like characteristics of large bivalve shell assemblages containing Pseudodon and Elongaria from Trinil HK indicate deliberate collection by a selective agent, possibly hominin.
Geological Society, London, Special Publications, 1996
ABSTRACT Two high resolution cores from the Spitsbergen margin were studied to increase the under... more ABSTRACT Two high resolution cores from the Spitsbergen margin were studied to increase the understanding of the palaeoceanography and deglaciation of the Spitsbergen continental margin. Planktonic and benthic foraminiferal δ18O records along with foraminiferal abundance counts and dropstone analysis were used to interpret the palaeoceanography of the Spitsbergen margin and to link the marine record with deglaciation of the Barents Sea Ice Sheet. High foraminiferal and dropstone abundances during the Late Weichselian glacial maximum show that this period was characterized by seasonally ice-free conditions. The initial deglaciation recognized along the Spitsbergen margin is dated at 14.1ka BP and represents the break up of the Barents Sea Ice Sheet, though some input from the Spitsbergen ice dome is likely. This initial deglaciation was produced by glacio-isostatic relative sea-level rise and/or by increased solar insolation after the minimum of the Late Weichselian. The first unequivocal deglaciation of Spitsbergen ice occurred at 13 ka, whereas the oceanographic regime was still dominated by polar waters. The beginning of the Holocene was heralded by a second deglaciation phase of the Spitsbergen ice mass. The first influx of North Atlantic waters causing rapid iceberg calving and melting was recorded at this time. Dropstone input virtually ended at approximately 9 ka BP when most glaciers had retreated beyond their present day positions. A short relatively cool episode produced by the retreat of the North Atlantic waters during the early Holocene was recorded along the Spitsbergen margin.
Geological Society, London, Special Publications, 2001
Ocean Drilling Program (ODP) Leg 171B recovered continuous sequences that yield evidence for a su... more Ocean Drilling Program (ODP) Leg 171B recovered continuous sequences that yield evidence for a suite of`critical' events in the Earth's history. The main events include the late Eocene radiolarian extinction, the late Palaeocene benthic foraminiferal extinction associated with the Late Palaeocene Thermal Maximum (LPTM), the Cretaceous± Palaeogene (K±P) extinction, the mid-Maastrichtian event, and several episodes of sapropel deposition documenting the late Cenomanian, late Albian and early Albian warm periods. A compilation of stable isotope results for foraminifera from Leg 171B sites and previously published records shows a series of large-scale cycles in temperature and d 13 C trends from Albian to late Eocene time. Evolution of d 18 O gradients between planktic and benthic foraminifera suggests that the North Atlantic evolved from a circulation system similar to the modern Mediterranean during early Albian time to a more open ocean circulation by late Albian±early Cenomanian time. Sea surface temperatures peaked during the mid-Cretaceous climatic optimum from the Albian±Cenomanian boundary to Coniacian time and then show a tendency to fall o toward the cool climates of the mid-Maastrichtian. The Albian± Coniacian period is characterized by light benthic oxygen isotope values showing generally warm deep waters. Lightest benthic oxygen isotopes occurred around the Cenomanian± Turonian boundary, and suggest middle bathyal waters with temperatures up to 20 8C in the North Atlantic. The disappearance of widespread sapropel deposition in Turonian time suggests that sills separating the North Atlantic from the rest of the global ocean were ®nally breached to sucient depth to permit ventilation by deep waters¯owing in from elsewhere. The Maastrichtian and Palaeogene records show two intervals of large-scale carbon burial and exhumation in the late Maastrichtian±Danian and late Palaeocene±early Eocene. Carbon burial peaked in early Danian time, perhaps in response to the withdrawal of large epicontinental seas from Europe and North America. Much of the succeeding Danian period was spent unroo®ng previously deposited carbon and repairing the damage to carbon export systems in the deep ocean caused by the K±P mass extinction. The youngest episode of carbon exhumation coincided with the onset of the early Eocene Warm Period and the LPTM, and has been attributed to the tectonic closure of the eastern Tethys and initiation of the Himalayan Orogeny.
New age data from Sr isotope analysis and both planktonic foraminifera and nannofossils are prese... more New age data from Sr isotope analysis and both planktonic foraminifera and nannofossils are presented and discussed here for the Upper Eocene-Upper Miocene sedimentary rocks of the Degirmenlik (Kythrea) Group. New dating is also given of some Cretaceous and Pliocene sediments. In a revised stratigraphy the Degirmenlik (Kythrea) Group is divided into ten formations. Different Upper Miocene formations are developed to the north and south of a regionally important, E-Wtrending syn-sedimentary fault. The samples were dated wherever possible by three independent methods, namely utilizing Sr isotopes, calcareous nannofossils and planktonic foraminifera. Some of the Sr isotopic dates are incompatible with the nannofossil and/or the planktonic foraminiferal dates. This is mainly due to reworking within gravity-deposited or current-affected sediments. When combined, the reliable age data allow an overall biostratigraphy and chronology to be erected. Several of the boundaries of previously defined formations are revised. Sr data that are incompatible with well-constrained biostratigraphical ages are commonly of Early Miocene age. This is attributed to a regional uplift event located to the east of Cyprus, specifically the collision of the Anatolian (Eurasian) and Arabian (African) plates during Early Miocene time. This study, therefore, demonstrates that analytically sound Sr isotopic ages can yield geologically misleading ages, particularly where extensive sediment reworking has occurred. Convincing ages are obtained when isotopic dating is combined with as many forms of biostratigraphical dating as possible, and this may also reveal previously unsuspected geological events (e.g. tectonic uplift or current activity).
Carbonate deposition began about 770 ka ago in a relatively deep-water slope environment and is r... more Carbonate deposition began about 770 ka ago in a relatively deep-water slope environment and is represented by a series of debris flows. Lithoclasts within these rocks, indicate that older limestones already existed in the area. Subsequent accretion involved the downslope ...
Deep Sea Research Part A. Oceanographic Research Papers, 1989
... Distributional pattern of planktonic foraminifers and pteropods in surface waters and top cor... more ... Distributional pattern of planktonic foraminifers and pteropods in surface waters and top core sediments of the Red Sea, and adjacent areas controlled by the monsoonal regime and other ecological factors ANABELLE AURAS-SCHUDNAGIES,*t DICK KROON,:~ GERALD ...
... Here, we present a Holocene stable O-isotope record from the summer-dwelling planktic foramin... more ... Here, we present a Holocene stable O-isotope record from the summer-dwelling planktic foraminifer G. bulloides in Core 905 off Somalia. ... The nucleus for the present work is a high-resolution study on Core 905 from the Arabian Sea off Somalia. Fig. 3 and Fig. ...
Two sediment cores from the Zaire Fan and the Angola Margin have been investigated for their comp... more Two sediment cores from the Zaire Fan and the Angola Margin have been investigated for their composition of terrigenous and biogenic constituents, respectively. For the late Quaternary, kaolinite/feldspar ratios and variations of terrigenous element ratios of Zr, Ti, K, Rb, and Al reveal that the composition of Zaire River sediment load has fluctuated in tune with precessional variations of boreal
1] Water column stratification increased at climatic transitions from cold to warm periods during... more 1] Water column stratification increased at climatic transitions from cold to warm periods during the late Quaternary and led to anoxic conditions and sapropel formation in the deep eastern Mediterranean basins. Highresolution data sets on sea-surface temperatures (SST) (estimated from U 37 k 0 indices) and d 18 O of planktonic foraminifer calcite (d 18 O fc ) across late Pleistocene sapropel intervals show that d 18 O fc decreased (between 1 and 4.6%) and SST increased (between 0.7°and 6.7°C). Maximal d 18 O seawater depletion of eastern Mediterranean surface waters at the transition is between 0.5 and 3.0%, and in all but one case exceeded the depletion seen in a western Mediterranean core. The depletion in d 18 O seawater is most pronounced at sapropel bases, in agreement with an initial sudden input of monsoon-derived freshwater. Most sapropels coincide with warming trends of SST. The density decrease by initial freshwater input and continued warming of the sea surface pooled fresh water in the surface layer and prohibited deep convection down to ageing deep water emplaced during cold and arid glacial conditions. An exception to this pattern is ''glacial'' sapropel S6; its largest d 18 O seawater depletion (3%) is almost matched by the depletion in the western Mediterranean Sea, and it is accompanied by surface water cooling following an initially rapid warming phase. A second period of significant isotopic depletion is in isotope stage 6 at the 150 kyr insolation maximum. While not expressed as a sapropel due to cold SST, it is in accord with a strengthened monsoon in the southern catchment.
Knowledge about dietary niche is key to understanding hominin evolution, since diet influences bo... more Knowledge about dietary niche is key to understanding hominin evolution, since diet influences body proportions, brain size, cognition, and habitat preference. In this study we provide ecological context for the current debate on modernity (or not) of aquatic resource exploitation by hominins. We use the Homo erectus site of Trinil as a case study to investigate how research questions on possible dietary relevance of aquatic environments can be addressed. Faunal and geochemical analysis of aquatic fossils from Trinil Hauptknochenschicht (HK) fauna demonstrate that Trinil at w1.5 Ma contained near-coastal rivers, lakes, swamp forests, lagoons, and marshes with minor marine influence, laterally grading into grasslands. Trinil HK environments yielded at least eleven edible mollusc species and four edible fish species that could be procured with no or minimal technology. We demonstrate that, from an ecological point of view, the default assumption should be that omnivorous hominins in coastal habitats with catchable aquatic fauna could have consumed aquatic resources. The hypothesis of aquatic exploitation can be tested with taphonomic analysis of aquatic fossils associated with hominin fossils. We show that midden-like characteristics of large bivalve shell assemblages containing Pseudodon and Elongaria from Trinil HK indicate deliberate collection by a selective agent, possibly hominin.
Geological Society, London, Special Publications, 1996
ABSTRACT Two high resolution cores from the Spitsbergen margin were studied to increase the under... more ABSTRACT Two high resolution cores from the Spitsbergen margin were studied to increase the understanding of the palaeoceanography and deglaciation of the Spitsbergen continental margin. Planktonic and benthic foraminiferal δ18O records along with foraminiferal abundance counts and dropstone analysis were used to interpret the palaeoceanography of the Spitsbergen margin and to link the marine record with deglaciation of the Barents Sea Ice Sheet. High foraminiferal and dropstone abundances during the Late Weichselian glacial maximum show that this period was characterized by seasonally ice-free conditions. The initial deglaciation recognized along the Spitsbergen margin is dated at 14.1ka BP and represents the break up of the Barents Sea Ice Sheet, though some input from the Spitsbergen ice dome is likely. This initial deglaciation was produced by glacio-isostatic relative sea-level rise and/or by increased solar insolation after the minimum of the Late Weichselian. The first unequivocal deglaciation of Spitsbergen ice occurred at 13 ka, whereas the oceanographic regime was still dominated by polar waters. The beginning of the Holocene was heralded by a second deglaciation phase of the Spitsbergen ice mass. The first influx of North Atlantic waters causing rapid iceberg calving and melting was recorded at this time. Dropstone input virtually ended at approximately 9 ka BP when most glaciers had retreated beyond their present day positions. A short relatively cool episode produced by the retreat of the North Atlantic waters during the early Holocene was recorded along the Spitsbergen margin.
Geological Society, London, Special Publications, 2001
Ocean Drilling Program (ODP) Leg 171B recovered continuous sequences that yield evidence for a su... more Ocean Drilling Program (ODP) Leg 171B recovered continuous sequences that yield evidence for a suite of`critical' events in the Earth's history. The main events include the late Eocene radiolarian extinction, the late Palaeocene benthic foraminiferal extinction associated with the Late Palaeocene Thermal Maximum (LPTM), the Cretaceous± Palaeogene (K±P) extinction, the mid-Maastrichtian event, and several episodes of sapropel deposition documenting the late Cenomanian, late Albian and early Albian warm periods. A compilation of stable isotope results for foraminifera from Leg 171B sites and previously published records shows a series of large-scale cycles in temperature and d 13 C trends from Albian to late Eocene time. Evolution of d 18 O gradients between planktic and benthic foraminifera suggests that the North Atlantic evolved from a circulation system similar to the modern Mediterranean during early Albian time to a more open ocean circulation by late Albian±early Cenomanian time. Sea surface temperatures peaked during the mid-Cretaceous climatic optimum from the Albian±Cenomanian boundary to Coniacian time and then show a tendency to fall o toward the cool climates of the mid-Maastrichtian. The Albian± Coniacian period is characterized by light benthic oxygen isotope values showing generally warm deep waters. Lightest benthic oxygen isotopes occurred around the Cenomanian± Turonian boundary, and suggest middle bathyal waters with temperatures up to 20 8C in the North Atlantic. The disappearance of widespread sapropel deposition in Turonian time suggests that sills separating the North Atlantic from the rest of the global ocean were ®nally breached to sucient depth to permit ventilation by deep waters¯owing in from elsewhere. The Maastrichtian and Palaeogene records show two intervals of large-scale carbon burial and exhumation in the late Maastrichtian±Danian and late Palaeocene±early Eocene. Carbon burial peaked in early Danian time, perhaps in response to the withdrawal of large epicontinental seas from Europe and North America. Much of the succeeding Danian period was spent unroo®ng previously deposited carbon and repairing the damage to carbon export systems in the deep ocean caused by the K±P mass extinction. The youngest episode of carbon exhumation coincided with the onset of the early Eocene Warm Period and the LPTM, and has been attributed to the tectonic closure of the eastern Tethys and initiation of the Himalayan Orogeny.
New age data from Sr isotope analysis and both planktonic foraminifera and nannofossils are prese... more New age data from Sr isotope analysis and both planktonic foraminifera and nannofossils are presented and discussed here for the Upper Eocene-Upper Miocene sedimentary rocks of the Degirmenlik (Kythrea) Group. New dating is also given of some Cretaceous and Pliocene sediments. In a revised stratigraphy the Degirmenlik (Kythrea) Group is divided into ten formations. Different Upper Miocene formations are developed to the north and south of a regionally important, E-Wtrending syn-sedimentary fault. The samples were dated wherever possible by three independent methods, namely utilizing Sr isotopes, calcareous nannofossils and planktonic foraminifera. Some of the Sr isotopic dates are incompatible with the nannofossil and/or the planktonic foraminiferal dates. This is mainly due to reworking within gravity-deposited or current-affected sediments. When combined, the reliable age data allow an overall biostratigraphy and chronology to be erected. Several of the boundaries of previously defined formations are revised. Sr data that are incompatible with well-constrained biostratigraphical ages are commonly of Early Miocene age. This is attributed to a regional uplift event located to the east of Cyprus, specifically the collision of the Anatolian (Eurasian) and Arabian (African) plates during Early Miocene time. This study, therefore, demonstrates that analytically sound Sr isotopic ages can yield geologically misleading ages, particularly where extensive sediment reworking has occurred. Convincing ages are obtained when isotopic dating is combined with as many forms of biostratigraphical dating as possible, and this may also reveal previously unsuspected geological events (e.g. tectonic uplift or current activity).
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Papers by D. Kroon