Evidence for Heinrich layers off Portugal (Tore Seamount: 39 °N, 12 °W)

Lebreiro, Susana Martin; Moreno, João; McCave, I. N.; Weaver, P. P. E.

doi:10.1016/0025-3227(95)00142-5

Cited by 105 publications

(61 citation statements)

References 25 publications

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“…At all sites, however, a trend of gradually increasing aridity over the MIS 4 interval is apparent (Fletcher et al, in press;Sánchez-Goñi et al, 2008). Since the study carried out by Lebreiro et al (1996), where the first evidence of Heinrich layers was found in marine sediments offshore Portugal, many other records, mostly from marine cores, have highlighted abrupt fluctuations in the Iberian climate during MIS 3 synchronous with HE and D/O cycles (e.g. Cacho et al, 1999;Frigola et al, 2008).…”

Section: The Iberian Climate Reconstruction During Last Glacial Cyclementioning

confidence: 97%

Northern Iberian abrupt climate change dynamics during the last glacial cycle: A view from lacustrine sediments

Moreno

González-Sampériz

Morellón

et al. 2012

Quaternary Science Reviews

130

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We present a palaeoclimatic reconstruction of the last glacial cycle in Iberia (ca. 120,000 -11,600 cal yrs BP) based on multiproxy reconstructions from lake sediments with robust chronologies, and with a particular focus on abrupt climate changes. The selected lake sequences provide an integrated approach from northern Iberia exploring temperature conditions, humidity variations and land-sea comparisons during the most relevant climate transitions of the last glacial period. Thus, we present evidence that demonstrates: i) cold but relatively humid conditions during the transition from MIS 5 to MIS 4, which prevailed until ca. 60,000 cal yrs BP in northern Iberia; ii) a general tendency towards greater aridity during MIS 4 and MIS 3 (ca 60,000 to 23,500 cal yrs BP) punctuated by abrupt climate changes related to Heinrich Events (HE), iii) a complex, highly variable climate during MIS 2 (23,500 to 14,600 cal yrs BP) with the "Mystery Interval" (MI: 18,500 to 14,600 cal yrs BP ) and not the global Last Glacial Maximum (LGM: 23,000 to 19,000 cal yrs BP) as the coldest and most arid period. The last glacial transition starts in synchrony with Greenland ice records at 14,600 cal yrs BP but the temperature increase was not so abrupt in the Iberian records and the highest humidity was attained during the Allerød (GI-1a to GI-1c) and not during the Bølling (GI-1e) period. The Younger Dryas event (GS-1) is discernible in northern Iberian lake records as a cold and dry interval, although Iberian vegetation records present a geographically variable signal for this interval, perhaps related to vegetation resilience.

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Section: The Iberian Climate Reconstruction During Last Glacial Cyclementioning

confidence: 97%

Northern Iberian abrupt climate change dynamics during the last glacial cycle: A view from lacustrine sediments

Moreno

González-Sampériz

Morellón

et al. 2012

Quaternary Science Reviews

130

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“…In the western Iberia offshore region, during the period 57 to 31 ka, climate was characterised by a succession of mild and wet periods (interstadials) alternating with cold and dry periods (stadials), related to the Dansgaard-Oescheger (D-O) cycles (Lebreiro et al, 1996;De Abreu et al, 2003;Roucoux et al, 2005). A succession of D-O cycles also occurred after 31 ka; however, in the 57 to 31 ka period ten D-O insterstadials occurred, while in the last 31 ka only four occurred.…”

Section: Tablementioning

confidence: 99%

“…The climate conditions were particularly severe during the Heinrich events (He) (Heinrich, 1988), of which there were three after 31 ka: at 30.2-29.0 ka (He3), 24.3-23.1 ka (He2) and 17.6-14.9 ka (He1) (Lebreiro et al, 1996). Pollen data indicate a dominance of open herbaceous vegetation, with increased areas of steppe in the period 31-23 ka (Roucoux et al, 2005).…”

Section: Tablementioning

confidence: 99%

Records of human occupation from Pleistocene river terrace and aeolian sediments in the Arneiro depression (Lower Tejo River, central eastern Portugal)

et al. 2012

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In the uppermost reach of the Lower Tejo River (eastern central Portugal), where the river crosses two quartzite ridges that separate the Ródão (upstream) and Arneiro (downstream) depressions, Palaeolithic artefacts have been recovered from three lower river terrace levels and a cover unit of aeolian sands. This paper presents data on the discovery of archaeological artefacts from the terrace levels and the aeolian sands that can be linked to Middle and Upper Palaeolithic industries from new field sites at Tapada do Montinho and Castelejo. The archaeological data when placed in a geomorphological, sedimentary and chronological framework, contribute new information on the understanding of human occupation in western Iberia during coldclimate episodes of the last 62 to 12 ka; and especially during the cooler and driest conditions that occurred between 32 and 12 ka, when the climate favoured aeolian sediment transport. In the Lower Tejo River, the integration of absolute age datasets with archaeological, geomorphological and sedimentary data indicate that in westernmost Iberia the first appearance of artefacts in river terrace sediments suggests that the earliest marker for human occupation dates from the lower Acheulian (Lower Palaeolithic), probably corresponding to an age of~340 ka. Data also suggest, for the first time, that Acheulian lithic industries were replaced by Middle Palaeolithic ones (namely the Levallois stone knapping technique) by~160 ka (~MIS6). Middle Palaeolithic industries were later replaced by Upper Palaeolithic industries at 32 ka. The post 32 ka period, dominated by aeolian sediment transport, is related to the onset of cold-dry climate conditions which resulted in low river flow discharges, floodplain exposure and reworking by NW winds. This colddry period is coeval with the disappearance of Megafauna and associated Neanderthal communities, and the replacement of the Middle Palaeolithic industries by Upper Palaeolithic ones in this westernmost part of Europe.

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“…For example, an IRD peak from the LIS is found sandwiched between two IRD peaks of European origin from a H-layer in the Bay of Biscay (Grousset et al, 2000;Zaragosi et al, 2001). In contrast to the Bay of Biscay records, H1 and H2 layers along the Portuguese margin show two depositional phases expressed by a weak basal peak that comprised detrital carbonate of LIS origin, and a top peak that consists of hematite-coated grains Auffret et al, 1996;Lebreiro et al, 1996;Bard et al, 2000).…”

Section: Synoptic Mixing Of Sediments In the North Atlantic During H1mentioning

confidence: 99%

Fine scale sediment structure and geochemical signature between eastern and western North Atlantic during Heinrich events 1 and 2

Rashid

Saint‐Ange

Barber

et al. 2012

Quaternary Science Reviews

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a b s t r a c tHeinrich iceberg-rafting events 1 and 2 (H1 and H2) in the Labrador Sea are identified by their typical nepheloid-flow deposit sedimentary structure, high bulk carbonate, increase in iceberg-rafted detritus (IRD), and depletion of d18 O in the surface-dwelling foraminifer, Neogloboquadrina pachyderma (s). Hlayers in this region have sedimentological characteristics different than those in the North Atlantic, and are consist of IRD interspersed in pelagic sediments. High resolution 14 C-AMS dates allowed us to delineate the leads and lags in instability between different ice-streams of the former Laurentide icesheet (LIS). Our data suggest that the discharge from the Hudson Strait ice-stream was followed by Cumberland Sound ice-sheet during H1 and H2. New radiogenic isotopes from the ice-proximal and surficial sediments of the greater Hudson Strait region and Labrador Sea H0, H1 and H2 layers suggest that carbonate-rich layers were only derived from Hudson Strait, not Baffin Bay. Fine scale structure of H1 and H2 intervals in Labrador Sea slope cores is characterized by two lithic peaks dominated by detrital carbonate grains and a single peak in cores from the central Labrador Sea. A similar pattern in the structure of H1 and H2 is observed along the western European margin. These findings contrast with North Atlantic H1 and H2 intervals, which are characterized by a peak of carbonate-rich grains, followed by a peak of quartz and volcanic grains. This comparison with North Atlantic and western European margin cores leads us to suggest that the coupling or lack thereof, between the LIS and European ice-sheet, is related to the depositional processes occurring along the margins, as well as the distance from the sources and the ability of the oceanic currents to disperse icebergs. Any significant change in ice-sheet dynamics would be recorded close to the ice-sheet margin, while distal locations would only record extreme events. We hypothesize that the discordance between the findings reported in the literature is most likely similar to the difference between the upper slope/ deep Labrador sites and the Flemish Pass site described in this contribution but requires vigorous testing.Crown

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Evidence for Heinrich layers off Portugal (Tore Seamount: 39 °N, 12 °W)

Cited by 105 publications

References 25 publications

Northern Iberian abrupt climate change dynamics during the last glacial cycle: A view from lacustrine sediments

Northern Iberian abrupt climate change dynamics during the last glacial cycle: A view from lacustrine sediments

Records of human occupation from Pleistocene river terrace and aeolian sediments in the Arneiro depression (Lower Tejo River, central eastern Portugal)

Fine scale sediment structure and geochemical signature between eastern and western North Atlantic during Heinrich events 1 and 2

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