- Email: [email protected]
Comparing Indian-Atlantic ocean exchange across multiple interglacials
Abstracts / Quaternary International 279-280 (2012) 346–461
up line up along the curved trace of the fault, one of which is the Mijia Mountains, whose eastern flank is bounded by the Yellow River valley. The mountain has a nearly flat summit, at an elevation of around 2200 m, which could testify to a young relief, undergoing fast upheaval while its surface is preserved. The river left a set of elongated terraces along the eastern flank of the Mijia Mountains. No terraces are visible elsewhere, which suggests that they are related to the mountain uplift rather than to a localized incision of the river. Cosmogenic dating (10Be and 26Al) of three terraces led to minimum ages of 9210, 13916 and 22125 kyrs. Taking into account a possible nonnegligible amount of erosion, the final rate of vertical movement range from 1.0 to 1.7 mm/yr. The difference in elevation between the river and the summit approximates 870 m, which suggest that uplift probably started w1 Myrs ago (if constant rate), in accordance with the young appearance of the massif. The bend of the fault on the northern flank of the push-up, around 13 to the west, means that around 20% of the fault movement can be absorbed trough shortening across the mountain. This would agree with slip rates of 5-10 mm/yr determined by previous studies on the fault.
377
reconstructed from a number sites, including Redhead Lagoon (Williams et al., 2006), Lake Baraba (Black et al., 2006), Caledonia Fen (Kershaw et al., 2007), Lake Leake (Dodson, 1975), Wyrie Swamp (Dodson, 1977), marine core E55-6 (Harle, 1997), Pulbeena Swamp (Colhoun et al., 1982), Tullabardine Dam (Colhoun and van der Geer 1986), Lake Selina (Colhoun et al., 1999), Egg Lagoon (D'Costa et al., 1993), and marine core SO36-7SL (Van De Geer et al., 1994). Although temperate eastern Australia is relatively wellrepresented, there are few records available from temperate Western Australia and the subtropics, with only two continuous subtropical records extending into the LGS are available, both from North Stradbroke Island (Petherick et al., 2008). In addition to inadequate spatial coverage, gaps in the current state of knowledge include uncertainties regarding the timing and nature of the LGM, with some records suggesting an early onset with an increasingly variable climate, while others supporting a more traditionally accepted cool arid phase lasting 3 – 4 kyr. The existence climatic reversals during the deglaciation (e.g. Heinrich-1, Antarctic Cold Reversal, Younger Dryas), a mid-Holocene climatic optimum and a late-Holocene arid phase are also unresolved. In addition, there are very few quantitative estimates of climate variables and a lack of knowledge of the timing and intensity human occupation.
THE LAST GLACIAL MAXIMUM IN EASTERN AUSTRALIA: MULTI-PROXY, HIGH RESOLUTION RECONSTRUCTIONS FROM LAKE SEDIMENT CORES ON NORTH STRADBROKE ISLAND
COMPARING INDIAN-ATLANTIC OCEAN EXCHANGE ACROSS MULTIPLE INTERGLACIALS
Lynda Petherick. The University of Queensland, Australia
Benjamin Petrick. Newcastle University, United Kingdom
E-mail address: [email protected]
E-mail address: [email protected]
Two continuous, high resolution records encompassing the LGM have been developed using multiple proxies (aeolian sediment flux, grain size, pollen, charcoal and geochemistry) in lake sediment from North Stradbroke Island (NSI), Australia. These records are unique in that they are the only continuous records extending into the LGM from the lowland subtropics of the Southern Hemisphere (SH). As such, they make a valuable contribution to enhancing our understanding of climatic variability in the region. The presence of Asteraceae (Tubilifloreae) and spineless Asteraceae (common indicators of glacial conditions in Australia) indicate significantly cooler temperatures (w6 C lower than today) in the subtropics during the LGM. Similarities between the vegetation at NSI and other temperate sites e.g. Caledonia Fen, Redhead Lagoon and Barrington Tops suggests that the NSI records reflect regional conditions across eastern Australia. The NSI records also suggest that the LGM was an extended period ca. 8 – 10 kyr, containing 2 arid phases (ca. 30 – 26.5 kyr & 21 – 19.5 kyr) separated by an interstadial. A growing number of records from across the SH also show evidence for an extended LGM that was not uniformly cool and dry. In addition, aeolian deposits were provenanced to continental source areas by geochemical fingerprinting, allowing the reconstruction of major dust transport pathways to NSI during the LGM. The position of dust transport pathways for eastern Australia provides new insight into synoptic-scale conditions. Our reconstructions show that westerly winds were regionally dominant during the 2 arid phases of the LGM, as implied by the chemistry of dust in the cores matching that of sediments from the Channel Country and Mulga Lands, both west of NSI. This suggests that the westerly wind belt shifted north during the 2 arid phases, and pole-ward during the interstadial, when southeasterly trade winds became more influential on NSI.
The Agulhas leakage into the Atlantic Ocean may be important for the magnitude and duration of interglacials. This heat and salt transfer from the Indian Ocean via Agulhas Leakage plays an important part in the global thermohaline circulation. Climate models and reconstructions have shown that changes to the strength of the heat transfer may cause major climatic changes and may play a role in transitions from glacials to interglacials. Here, we present results from ODP Site 1087 (3128’S, 15190 E) to investigate how Agulhas Leakage may have changed during the middle and late Pleistocene (0 – 1.5 million years ago). Site 1087 is located near the input of the leakage into the Atlantic Ocean. Reconstructing the temperature history of this site will provide an important data set for investigating the Agulhas Current contribution to the Atlantic Ocean during both the 41 kyr and 100 kyr worlds. Our approach is to apply several organic geochemistry proxies and dinoflagellate cyst assemblage analyses to reconstruct the Pleistocene history of Site 1087, including UK37’ index reconstructions of sea surface temperature (SST). Initial results show that the greatest amount of SST warming often precedes decreases in benthic d18O and therefore occurs early in transitions to interglacials. The most significant of these is a rapid increase in SSTs w10 kyr before the onset of the Marine Isotope Stage 11 ‘super’ interglacial. Significantly, the early warmth exceeds SSTs recorded for the rest of the interglacial. The end of interglacial warmth is also marked by increased pigment accumulation during some transitions to glacial conditions, which may be related to either enhanced upwelling, a shift in the polar fronts, or variations in the strength of the Agulhas leakage. All of these signals suggest that changes in the Agulhas leakage occur at the beginning and end of interglacial periods, and may offer important insights into how this system affected interglacial amplitude and duration.
TEMPERATE RECORDS FROM AUSTRALIA ON INTIMATE TIMESCALES: A SUMMARY
REGIONAL ADAPTATIONS OF THE BRITISH LATE MAGDALENIAN CRESWELLIAN VARIANT: NEW RESEARCH
Lynda Petherick. The University of Queensland, Australia E-mail address: [email protected]
Paul Pettitt. Sheffield University, United Kingdom E-mail address: p.pettitt@sheffield.ac.uk
The aim here is to present an overview of the current state of knowledge of climatic and environmental variability in temperate Australia as part of the Aus-INTIMATE project. The synthesis of temperate records from Australia will ultimately aid in developing a robust chronology and identify significant periods of climatic and environmental variability for the region. There are several continuous records of past climatic and environmental variability from temperate eastern Australia, predominantly based on pollen and charcoal archives in lake sediments. Long records have been
This paper presents the results of recent research into the British Late Magdalenian ('Creswellian') in regional context. Following the discovery of Britain's first examples of cave art in 2003, which have been ascribed to the Late Magdalenian, new excavations have been conducted outside Church Hole (cave), Creswell. These have uncovered a new rockshelter below Church Hole ('The Crypt') which contains an in situ Late Magdalenian lithic assemblage in association with well-preserved fauna including reindeer,
up line up along the curved trace of the fault, one of which is the Mijia Mountains, whose eastern flank is bounded by the Yellow River valley. The mountain has a nearly flat summit, at an elevation of around 2200 m, which could testify to a young relief, undergoing fast upheaval while its surface is preserved. The river left a set of elongated terraces along the eastern flank of the Mijia Mountains. No terraces are visible elsewhere, which suggests that they are related to the mountain uplift rather than to a localized incision of the river. Cosmogenic dating (10Be and 26Al) of three terraces led to minimum ages of 9210, 13916 and 22125 kyrs. Taking into account a possible nonnegligible amount of erosion, the final rate of vertical movement range from 1.0 to 1.7 mm/yr. The difference in elevation between the river and the summit approximates 870 m, which suggest that uplift probably started w1 Myrs ago (if constant rate), in accordance with the young appearance of the massif. The bend of the fault on the northern flank of the push-up, around 13 to the west, means that around 20% of the fault movement can be absorbed trough shortening across the mountain. This would agree with slip rates of 5-10 mm/yr determined by previous studies on the fault.
377
reconstructed from a number sites, including Redhead Lagoon (Williams et al., 2006), Lake Baraba (Black et al., 2006), Caledonia Fen (Kershaw et al., 2007), Lake Leake (Dodson, 1975), Wyrie Swamp (Dodson, 1977), marine core E55-6 (Harle, 1997), Pulbeena Swamp (Colhoun et al., 1982), Tullabardine Dam (Colhoun and van der Geer 1986), Lake Selina (Colhoun et al., 1999), Egg Lagoon (D'Costa et al., 1993), and marine core SO36-7SL (Van De Geer et al., 1994). Although temperate eastern Australia is relatively wellrepresented, there are few records available from temperate Western Australia and the subtropics, with only two continuous subtropical records extending into the LGS are available, both from North Stradbroke Island (Petherick et al., 2008). In addition to inadequate spatial coverage, gaps in the current state of knowledge include uncertainties regarding the timing and nature of the LGM, with some records suggesting an early onset with an increasingly variable climate, while others supporting a more traditionally accepted cool arid phase lasting 3 – 4 kyr. The existence climatic reversals during the deglaciation (e.g. Heinrich-1, Antarctic Cold Reversal, Younger Dryas), a mid-Holocene climatic optimum and a late-Holocene arid phase are also unresolved. In addition, there are very few quantitative estimates of climate variables and a lack of knowledge of the timing and intensity human occupation.
THE LAST GLACIAL MAXIMUM IN EASTERN AUSTRALIA: MULTI-PROXY, HIGH RESOLUTION RECONSTRUCTIONS FROM LAKE SEDIMENT CORES ON NORTH STRADBROKE ISLAND
COMPARING INDIAN-ATLANTIC OCEAN EXCHANGE ACROSS MULTIPLE INTERGLACIALS
Lynda Petherick. The University of Queensland, Australia
Benjamin Petrick. Newcastle University, United Kingdom
E-mail address: [email protected]
E-mail address: [email protected]
Two continuous, high resolution records encompassing the LGM have been developed using multiple proxies (aeolian sediment flux, grain size, pollen, charcoal and geochemistry) in lake sediment from North Stradbroke Island (NSI), Australia. These records are unique in that they are the only continuous records extending into the LGM from the lowland subtropics of the Southern Hemisphere (SH). As such, they make a valuable contribution to enhancing our understanding of climatic variability in the region. The presence of Asteraceae (Tubilifloreae) and spineless Asteraceae (common indicators of glacial conditions in Australia) indicate significantly cooler temperatures (w6 C lower than today) in the subtropics during the LGM. Similarities between the vegetation at NSI and other temperate sites e.g. Caledonia Fen, Redhead Lagoon and Barrington Tops suggests that the NSI records reflect regional conditions across eastern Australia. The NSI records also suggest that the LGM was an extended period ca. 8 – 10 kyr, containing 2 arid phases (ca. 30 – 26.5 kyr & 21 – 19.5 kyr) separated by an interstadial. A growing number of records from across the SH also show evidence for an extended LGM that was not uniformly cool and dry. In addition, aeolian deposits were provenanced to continental source areas by geochemical fingerprinting, allowing the reconstruction of major dust transport pathways to NSI during the LGM. The position of dust transport pathways for eastern Australia provides new insight into synoptic-scale conditions. Our reconstructions show that westerly winds were regionally dominant during the 2 arid phases of the LGM, as implied by the chemistry of dust in the cores matching that of sediments from the Channel Country and Mulga Lands, both west of NSI. This suggests that the westerly wind belt shifted north during the 2 arid phases, and pole-ward during the interstadial, when southeasterly trade winds became more influential on NSI.
The Agulhas leakage into the Atlantic Ocean may be important for the magnitude and duration of interglacials. This heat and salt transfer from the Indian Ocean via Agulhas Leakage plays an important part in the global thermohaline circulation. Climate models and reconstructions have shown that changes to the strength of the heat transfer may cause major climatic changes and may play a role in transitions from glacials to interglacials. Here, we present results from ODP Site 1087 (3128’S, 15190 E) to investigate how Agulhas Leakage may have changed during the middle and late Pleistocene (0 – 1.5 million years ago). Site 1087 is located near the input of the leakage into the Atlantic Ocean. Reconstructing the temperature history of this site will provide an important data set for investigating the Agulhas Current contribution to the Atlantic Ocean during both the 41 kyr and 100 kyr worlds. Our approach is to apply several organic geochemistry proxies and dinoflagellate cyst assemblage analyses to reconstruct the Pleistocene history of Site 1087, including UK37’ index reconstructions of sea surface temperature (SST). Initial results show that the greatest amount of SST warming often precedes decreases in benthic d18O and therefore occurs early in transitions to interglacials. The most significant of these is a rapid increase in SSTs w10 kyr before the onset of the Marine Isotope Stage 11 ‘super’ interglacial. Significantly, the early warmth exceeds SSTs recorded for the rest of the interglacial. The end of interglacial warmth is also marked by increased pigment accumulation during some transitions to glacial conditions, which may be related to either enhanced upwelling, a shift in the polar fronts, or variations in the strength of the Agulhas leakage. All of these signals suggest that changes in the Agulhas leakage occur at the beginning and end of interglacial periods, and may offer important insights into how this system affected interglacial amplitude and duration.
TEMPERATE RECORDS FROM AUSTRALIA ON INTIMATE TIMESCALES: A SUMMARY
REGIONAL ADAPTATIONS OF THE BRITISH LATE MAGDALENIAN CRESWELLIAN VARIANT: NEW RESEARCH
Lynda Petherick. The University of Queensland, Australia E-mail address: [email protected]
Paul Pettitt. Sheffield University, United Kingdom E-mail address: p.pettitt@sheffield.ac.uk
The aim here is to present an overview of the current state of knowledge of climatic and environmental variability in temperate Australia as part of the Aus-INTIMATE project. The synthesis of temperate records from Australia will ultimately aid in developing a robust chronology and identify significant periods of climatic and environmental variability for the region. There are several continuous records of past climatic and environmental variability from temperate eastern Australia, predominantly based on pollen and charcoal archives in lake sediments. Long records have been
This paper presents the results of recent research into the British Late Magdalenian ('Creswellian') in regional context. Following the discovery of Britain's first examples of cave art in 2003, which have been ascribed to the Late Magdalenian, new excavations have been conducted outside Church Hole (cave), Creswell. These have uncovered a new rockshelter below Church Hole ('The Crypt') which contains an in situ Late Magdalenian lithic assemblage in association with well-preserved fauna including reindeer,