title: Intra-conference and Post-conference Tour Guides, International Inter-INQUA Field Conference and Workshop on Tephrochronology, Loess, and Paleopedology

authors: Lowe, David J.

abstract: New Zealand consists of a cluster of islands, the three largest being North, South, and Stewart, in the southwest Pacific Ocean. They have a total land area of about 270 000 km2 (similar to that of the British Isles or Japan). The islands are the small emergent parts of a much larger submarine continental mass (Fig. 0.1) that was rafted away from Australia and Antarctica by sea-floor spreading in the proto-Tasman Sea between 85 and 60 Ma. Much of this New Zealand subcontinent is a remnant of the former eastern margin of Gondwanaland, the ancient southern supercontinent. The mainland islands form a long, narrow, NE-SW trending archipelago bisected by an active, obliquely converging, boundary between the Australian and Pacific lithospheric plates (Fig. 0.2), which has evolved over the last 25 million years (Kamp 1992). The plate boundary is marked by active seismicity and volcanic arcs, illustrating New Zealand's position as part of the Circum-Pacific Mobile Belt -the so-called "Pacific Ring of Fire". The NE-SW trend of the modem plate boundary cuts across mainly NW-SE oriented structural features inherited from earlier (mid-Cretaceous) rifting events.

text: Intra-conference and Post-conference Tour Guides, International Inter-INQUA Field Conference and Workshop on Tephrochronology, Loess, and Paleopedology New Zealand consists of a cluster of islands, the three largest being North, South, and Stewart, in the southwest Pacific Ocean. They have a total land area of about 270 000 km2 (similar to that of the British Isles or Japan). The islands are the small emergent parts of a much larger submarine continental mass (Fig. 0.1) that was rafted away from Australia and Antarctica by sea-floor spreading in the proto-Tasman Sea between 85 and 60 Ma. Much of this New Zealand subcontinent is a remnant of the former eastern margin of Gondwanaland, the ancient southern supercontinent. The mainland islands form a long, narrow, NE-SW trending archipelago bisected by an active, obliquely converging, boundary between the Australian and Pacific lithospheric plates (Fig. 0.2), which has evolved over the last 25 million years (Kamp 1992). The plate boundary is marked by active seismicity and volcanic arcs, illustrating New Zealand's position as part of the Circum-Pacific Mobile Belt -the so-called "Pacific Ring of Fire". The NE-SW trend of the modem plate boundary cuts across mainly NW-SE oriented structural features inherited from earlier (mid-Cretaceous) rifting events.

year: 1994-02-01

title: Benthic foraminiferal response to changes in bottom-water oxygenation and organic carbon flux in the eastern Mediterranean during LGM to Recent times

authors: Abu-Zied, Ramadan H.

subjects: benthic foraminifera

abstract: We present a high-resolution study of benthic foraminiferal abundances in 4 cores from the central Aegean and NE Levantine Seas, spanning the interval from 30 ka BP to the present. The benthic foraminiferal faunas indicate that during LGM times, bottom waters were well ventilated, while organic flux to the sea floor was significantly higher than today. From 30 to 10.2 ka BP, faunal density and composition suggest a gradual decrease in organic flux to the sea floor. This trend is interrupted by a short return to higher organic flux levels during the Younger Dryas (12.8–11.5 ka BP). The faunas immediately preceding the early to middle Holocene organic-rich layer (sapropel) S1 are very similar to Late Holocene faunas, indicating oligotrophic conditions. The transition from well ventilated bottom waters to anoxic (Levantine Basin) or strongly dysoxic (Aegean Sea) bottom waters appears to take place within a time-span of only 600 years, from ∼ 10.8 to 10.2 ka BP. Sapropel S1 (10.2–6.4 ka BP) is characterized by extended periods of bottom-water anoxia in the Levantine Basin, and by strongly dysoxic conditions punctuated by episodic re-ventilation events in the Aegean Sea. Re-establishment of fully oxygenated bottom-water conditions after sapropel S1 was extremely rapid. The ensuing Late Holocene faunas are very similar to recent faunas found in the Aegean Sea, suggesting much lower fluxes of organic matter to the sea floor than during glacial times.

text: Benthic foraminiferal response to changes in bottom-water oxygenation and organic carbon flux in the eastern Mediterranean during LGM to Recent times We present a high-resolution study of benthic foraminiferal abundances in 4 cores from the central Aegean and NE Levantine Seas, spanning the interval from 30 ka BP to the present. The benthic foraminiferal faunas indicate that during LGM times, bottom waters were well ventilated, while organic flux to the sea floor was significantly higher than today. From 30 to 10.2 ka BP, faunal density and composition suggest a gradual decrease in organic flux to the sea floor. This trend is interrupted by a short return to higher organic flux levels during the Younger Dryas (12.8–11.5 ka BP). The faunas immediately preceding the early to middle Holocene organic-rich layer (sapropel) S1 are very similar to Late Holocene faunas, indicating oligotrophic conditions. The transition from well ventilated bottom waters to anoxic (Levantine Basin) or strongly dysoxic (Aegean Sea) bottom waters appears to take place within a time-span of only 600 years, from ∼ 10.8 to 10.2 ka BP. Sapropel S1 (10.2–6.4 ka BP) is characterized by extended periods of bottom-water anoxia in the Levantine Basin, and by strongly dysoxic conditions punctuated by episodic re-ventilation events in the Aegean Sea. Re-establishment of fully oxygenated bottom-water conditions after sapropel S1 was extremely rapid. The ensuing Late Holocene faunas are very similar to recent faunas found in the Aegean Sea, suggesting much lower fluxes of organic matter to the sea floor than during glacial times.

year: 2008

title: A discontinuous ca. 80 ka record of Late Quaternary environmental change from Lake Omapere, Northland, New Zealand

authors: Newnham, Rewi M.

subjects: Last Glacial

abstract: We present an integrated record of environmental change from Lake Omapere, Northland, New Zealand, based on palaeolimnological analysis of a 7-m-long core and eight adjunct cores spanning part of the last 80 calendar (cal.) ka. The chronology was developed using tephrochronology, palaeomagnetism and radiocarbon dating together with climato- and palyno-stratigraphy. Two of 14 tephra layers in the cores provide markers for correlating the record with other New Zealand climato-stratigraphic sequences, deep-sea cores and the global marine isotope record. Pollen, diatom, palaeomagnetic, sedimentologic and pigment analyses show that Lake Omapere, currently 2 m deep, has had a discontinuous history. Occupying a shallow basin perched partly within old basalt lavas, the initial (alkaline) lake formed towards the end of MIS 5a at ca. 80 cal. ka, presumably because of blockage of local drainage of a swampy alluvial floodplain, inundating peat deposits and forest trees, including kauri (Agathis australis). The lake filled rapidly to a level 1–2 m above that at present. Such filling was probably unrelated to climate but a subsequent phase of variable but generally falling lake levels and increasing dystrophy may have been climatically controlled, commencing during MIS 4 and culminating in periods early in MIS 3 when the lake became swampy or dry. Conditions of non-deposition (or non-preservation) obtained for most of the period after ca. 55 cal. ka (Rotoehu Ash) until formation of the modern lake approximately 600–700 cal. years ago or soon after, as indicated by the presence of Tephra-1, identified in part as Kaharoa Tephra (AD 1314), near the top of the core. The modern lake originated possibly through damming of the western outlet as a consequence of accelerated erosion accompanying earliest Polynesian deforestation, an interpretation supported by Maori oral tradition.
The pollen record indicates that beech Nothofagus (presumably N. truncata) was much more common in Northland during the Last Glacial, and that for this region the relative abundance of Nothofagus vs. Agathis pollen serves as a better indicator of cooler versus warmer intervals during the Quaternary than the ratio of tree to non-tree pollen. However, it seems likely that moisture balance was a more critical factor than temperature in vegetation composition and distribution, particularly during the LGM, and the long periods of hiatus may also be linked to a drier climate than present. Correlation coefficients between the pollen curves confirm that several tree species (Halocarpus bidwillii, H. biformis and Phyllocladus alpinus), previously palynologically concealed within generic taxonomic groups, occurred about two degrees latitude further north and at a much lower altitude than their current limits during cooler or drier phases of the Last Glacial. A temperature depression in Northland of 4 °C at various times during the Last Glacial is inferred from these range expansions. Nevertheless, the persistence of widespread forest cover suggests that the late Pleistocene climate of Northland was less severe than for most of the rest of New Zealand and strengthens the argument for a heightened temperature gradient across northern New Zealand during the Last Glacial.

text: A discontinuous ca. 80 ka record of Late Quaternary environmental change from Lake Omapere, Northland, New Zealand We present an integrated record of environmental change from Lake Omapere, Northland, New Zealand, based on palaeolimnological analysis of a 7-m-long core and eight adjunct cores spanning part of the last 80 calendar (cal.) ka. The chronology was developed using tephrochronology, palaeomagnetism and radiocarbon dating together with climato- and palyno-stratigraphy. Two of 14 tephra layers in the cores provide markers for correlating the record with other New Zealand climato-stratigraphic sequences, deep-sea cores and the global marine isotope record. Pollen, diatom, palaeomagnetic, sedimentologic and pigment analyses show that Lake Omapere, currently 2 m deep, has had a discontinuous history. Occupying a shallow basin perched partly within old basalt lavas, the initial (alkaline) lake formed towards the end of MIS 5a at ca. 80 cal. ka, presumably because of blockage of local drainage of a swampy alluvial floodplain, inundating peat deposits and forest trees, including kauri (Agathis australis). The lake filled rapidly to a level 1–2 m above that at present. Such filling was probably unrelated to climate but a subsequent phase of variable but generally falling lake levels and increasing dystrophy may have been climatically controlled, commencing during MIS 4 and culminating in periods early in MIS 3 when the lake became swampy or dry. Conditions of non-deposition (or non-preservation) obtained for most of the period after ca. 55 cal. ka (Rotoehu Ash) until formation of the modern lake approximately 600–700 cal. years ago or soon after, as indicated by the presence of Tephra-1, identified in part as Kaharoa Tephra (AD 1314), near the top of the core. The modern lake originated possibly through damming of the western outlet as a consequence of accelerated erosion accompanying earliest Polynesian deforestation, an interpretation supported by Maori oral tradition.
The pollen record indicates that beech Nothofagus (presumably N. truncata) was much more common in Northland during the Last Glacial, and that for this region the relative abundance of Nothofagus vs. Agathis pollen serves as a better indicator of cooler versus warmer intervals during the Quaternary than the ratio of tree to non-tree pollen. However, it seems likely that moisture balance was a more critical factor than temperature in vegetation composition and distribution, particularly during the LGM, and the long periods of hiatus may also be linked to a drier climate than present. Correlation coefficients between the pollen curves confirm that several tree species (Halocarpus bidwillii, H. biformis and Phyllocladus alpinus), previously palynologically concealed within generic taxonomic groups, occurred about two degrees latitude further north and at a much lower altitude than their current limits during cooler or drier phases of the Last Glacial. A temperature depression in Northland of 4 °C at various times during the Last Glacial is inferred from these range expansions. Nevertheless, the persistence of widespread forest cover suggests that the late Pleistocene climate of Northland was less severe than for most of the rest of New Zealand and strengthens the argument for a heightened temperature gradient across northern New Zealand during the Last Glacial.

year: 2004