Miocene To Holocene Diatom Biostratigraphy from Baffin Bay and Labrador Sea, Ocean Drilling Program Sites 645 and 646

Analyses of marine and terrestrial palynomorphs of Ocean Drilling Program (ODP) Site 645 in Baffin Bay led us to define a new biostratigraphical scheme covering the late Miocene to Pleistocene based on dinocyst and acritarch assemblages. Four biozones were defined. The first one, from 438.6 m below sea floor (mbsf) to 388 mbsf, can be assigned a late Miocene to early Pliocene age (>4.5 Ma), based on the common occurrence of Cristadinium diminutivum and Selenopemphix brevispinosa. Biozone 2, spanning from an erosional unconformity to a recovery hiatus, is marked by the highest occurrences (HOs) of Veriplicidium franklinii and Cristadinium diminutivum, which suggest an early Pliocene age >3.6 Ma (∼4.5 to ∼3.6 Ma). Biozone 3, above the recovery hiatus and up to 220.94 mbsf, corresponds to a late Pliocene or early Pleistocene age based on occurrences of Bitectatodinium readwaldii, Cymatiosphaera? icenorum, and Lavradosphaera canalis. Finally, between 266.4 and 120.56 mbsf, Biozone 4, marked by the HO of Filisphaera filifera, Filisphaera microornata, and Habibacysta tectata, has an early Pleistocene age (>1.4 Ma). Our biostratigraphy implies that horizon b1 of the Baffin Bay seismic stratigraphy corresponds to the recovery hiatus at ODP Site 645, which suggests a very thick Pliocene sequence along the Baffin Island slope. Dinocyst assemblages and terrestrial palynomorphs in our records indicate that the late Miocene and (or) early Pliocene were characterized by relatively warm coastal surface waters and boreal forest or forested tundra vegetation over adjacent lands. In contrast, the early Pleistocene dinocyst assemblages above the recovery hiatus indicate cold surface waters, while pollen data suggest reduced vegetation cover on adjacent lands.

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Changes in the silt- and clay-size mineralogy of sediments at Ocean Drilling Program site 645B, Baffin Bay

Canadian Journal of Earth Sciences ◽

10.1139/e93-211 ◽

1993 ◽

Vol 30 (12) ◽

pp. 2448-2452 ◽

Cited By ~ 11

Author(s):

J. T. Andrews

Keyword(s):

Baffin Island ◽

X Ray Diffraction ◽

Ocean Drilling Program ◽

Sea Floor ◽

X Ray ◽

Baffin Bay ◽

Ocean Drilling ◽

Limited Supply ◽

Detrital Carbonate ◽

Island Shelf

Site 645B, Ocean Drilling Program (ODP) leg 105, was cored in 2010 m water depth off the eastern margin of Baffin Island. A 279 m core was dated as extending back to ca. 2 Ma. Samples of sediment were analyzed for their silt- and clay-size mineralogy using X-ray diffraction techniques. Constrained cluster analysis on these data defined three units, which indicated that significant changes in mineralogies occurred at approximately 75 m below sea floor (bsf) (ca. 0.5 Ma) and 155 m bsf (ca. 1.15 Ma). These boundaries coincide closely with units IA–IB and IB–II as designated in the ODP shipboard reports, and which were based on detrital carbonate and sand contents. Unit II (1.2–2 Ma) is characterized by zero clay-size calcite and high amounts of clay-size smectite and silt-size mica. Unit IB (0.5 – 1.15 Ma) is noteworthy for the first presence of clay-size calcite, high amounts of detrital dolomite, and a peak in clay-size kaolinite. The uppermost unit IA (0–0.5 Ma) is characterized by consistently high values of clay-size dolomite and sand. Compared with sediments on the adjacent eastern Baffin Island shelf and fiords, the sediments at ODP site 645B are enhanced in the amounts of carbonate, smectite, and kaolinite, and depleted in both silt- and clay-size mica and feldspar. This pattern suggests a limited supply of sediment is transported from Baffin Island into Baffin Bay.

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Ocean drilling program [ODP] site survey [Hudson 84-030] in the Labrador Sea: 3.5 kHz profiles

10.4095/120225 ◽

1985 ◽

Author(s):

S K Chough ◽

D C Mosher ◽

S P Srivastava

Keyword(s):

Labrador Sea ◽

Ocean Drilling Program ◽

Ocean Drilling ◽

Site Survey

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Dinocyst and acritarch biostratigraphy of the Late Pliocene to Early Pleistocene at Integrated Ocean Drilling Program Site U1307 in the Labrador Sea

Journal of Micropalaeontology ◽

10.5194/jm-39-41-2020 ◽

2020 ◽

Vol 39 (1) ◽

pp. 41-60

Author(s):

Aurélie Marcelle Renée Aubry ◽

Stijn De Schepper ◽

Anne de Vernal

Keyword(s):

North Atlantic ◽

Early Pleistocene ◽

Labrador Sea ◽

Ocean Drilling Program ◽

Late Pliocene ◽

Ocean Drilling ◽

The North ◽

Integrated Ocean Drilling Program ◽

Basin Scale ◽

The North Atlantic

Abstract. We have analyzed marine palynomorphs (mainly dinocysts and acritarchs) from the Integrated Ocean Drilling Program Site U1307 in the Labrador Sea in order to establish a detailed biostratigraphy for the Late Pliocene to Early Pleistocene. We have defined three magnetostratigraphically calibrated dinocyst and acritarch biozones in the Late Pliocene to Early Pleistocene. Zone LS1 is defined based on the highest occurrence of Barssidinium graminosum and covers the later Pliocene from 3.21 to 2.75 Ma. Zone LS2 is marked by the acme of Pyxidinopsis braboi which occurs between 2.75 and 2.57 Ma, thus encompassing the Plio–Pleistocene transition. Finally, zone LS3 extends from 2.57 to 2.23 Ma in the Early Pleistocene. The palynostratigraphic record of IODP Site U1307 is difficult to correlate to other North Atlantic and Nordic Seas sites mainly because of a different temporal resolution and a lack of well-defined biostratigraphic marker species at the basin scale. The low abundance, discontinuous occurrence and asynchronous events of warm-water Pliocene taxa such as Invertocysta lacrymosa, Impagidinium solidum, Ataxiodinium confusum, Melitasphaeridium choanophorum and Operculodinium? eirikianum suggest cooler conditions in the Labrador Sea than elsewhere in the North Atlantic, reflecting a strong regionalism. Nevertheless, as recorded at other locations in the North Atlantic, the disappearance of many dinocyst and acritarch taxa around 2.75 Ma at Site U1307 reflects a strong ecological response accompanying the intensification of the Northern Hemisphere glaciation.

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