X-Ray Mineralogy Studies, Leg 48Rockall Region (Sites 403, 404, 405, and 406)

This X-ray mineralogy study of Tertiary samples recovered from Rockall sites permitted the definition of four mineralogical units and the tracing of the paleoenvironmental evolution in this region. INTRODUCTION The following mineralogical units were defined on the basis of our study: Unit I (upper Paleocene) is characterized by the occurrence of quartz and feldspars as well as by that of clay minerals, namely smectite, illite, kaolinite, and chlorite. Deposits are of a quite marked detrital nature. Unit II (lower Eocene) consists of sediments represented by plagioclase feldspars and zeolites; the major clay mineral components are smectites. These deposits suggest a sedimentation influenced by a basic volcanic environment. The presence of layers rich in kaolinite (Site 555) probably indicates terrigenous inputs developed under leaching warm climates. Unit III (middle Eocene to middle Miocene) is marked by a high carbonate content and dominantly smectite clay minerals: zeolites persist. Sedimentation is of pelagic type attesting to the impact of basic volcanism and/or that of fine-grained terrigenous inputs developed under warm climates with contrasting seasons. Unit IV (from middle/upper Miocene) is also characterized by high carbonate contents. Clay minerals are highly variable (smectite, illite, kaolinite, chlorite). This change in mineralogical composition suggests climatic cooling linked to a change in the hydrological exchanges between the Norwegian Sea and North Atlantic. METHODS Analyses X-ray diffraction was used on a total of 167 Paleocene and Miocene samples. The diffractometer used was a Philips 1310 and operating conditions were as follows: nickle-filtered copper Kα radiation at 40 kv, 20 mA. Total Sediments Dried and pulverized samples of total sediments were analyzed according to the powder diffractogram method. Semiquantitative values of quartz, calcite, and feldspars (K and plagioclase) were estimated from peak heights by comparison with mixed synthetic reference samples. Zeolites were estimated by relative frequencies as abundant, present, or trace on the basis of height of characteristic reflections.

Section: Tertiary Sedimentation: Comparison With Leg 48 Resultsmentioning

confidence: 99%

Section: Mineralogical Unitmentioning

confidence: 99%

X-Ray Mineralogy Study of Tertiary Deposits, Leg 81, Sites 552555

Latouche¹

1984

“…Smectites are the most common clay minerals. More or less well crystallized, they sometimes display a slow swelling in glycol ethylene (Fan and Zemmels, 1972), a characteristic already recognized in the altered clays from volcanic material in the region of Rockall (Latouche and Maillet, 1979).…”

Section: Mineralogymentioning

confidence: 85%

“…The high frequency of smectites seems to be related to the occurrence of volcanic material such as glass and rock debris which often constitute most of the sediment. It has often been hypothesized that smectites formed in situ through underwater alteration of this volcanic matter (Yeroshev-Shak, 1964;Bonatti, 1967;Seyfried and Bischoff, 1977;Couture, 1977;Seyfried et al, 1978;Latouche et Maillet, 1979). Their frequent association with Plagioclase feldspars and zeolites (particularly phillipsite) supports this hypothesis.…”

Section: )mentioning

confidence: 96%

X-Ray Mineralogy Studies, Deep Sea Drilling Project Leg 60

Latouche¹,

Maillet²,

Blanchet³

1982

Self Cite

A bulk-sediment and clay-fraction X-ray diffraction study of samples from Deep Sea Drilling Project Leg 60 shows an abundance of the following minerals: Plagioclase feldspar, zeolite, smectite, Fe-Mg chlorite, attapulgite, and serpentine. Amorphous compounds are also abundant. The variations in abundance of the different components correspond to episodes of volcanic activity through time. Deposits from periods of great activity are composed of sediments very rich in amorphous matter and in "primary" minerals (e.g., Plagioclase feldspars). During relatively quiet periods, clay minerals and zeolites predominate.

“…In the North Atlantic, previous clay-mineral studies of the Tertiary stratigraphic sequence include: Latouche (1979), Latouche and Maillet (1979), and Debrabant et al (1979). Latouche (1979) summarizes the region's clay-mineral stratigraphy as consisting of three successive sedimentary episodes: an early Cenozoic environment of highly variable sedimentation under depositional conditions peculiar to individual basins, a late Eocene transitional phase, and the modern phase with uniform pelagic sedimentation over the entire northeastern Atlantic region.…”

Section: Introductionmentioning

confidence: 99%

Lithostratigraphy and Clay Mineralogy of the Western Margin of the Rockall Plateau and the Hatton Sediment Drift

Zimmerman¹

1984

Learning more about the history of oceanic sedimentation and its relationship to the development of abyssal circulation in the northeastern Atlantic was a major objective of Leg 81 drilling. Accordingly, sites were situated on an EastWest traverse across the southwestern margin of Rockall Plateau and the Hatton Drift. All sites had a similar stratigraphic sequence of late Paleocene-early Eocene volcanogenic/shallow-water sediments lying below a major late Eocene-Miocene unconformity. Overlying this hiatus was a sediment-drift sequence of Mio-Pliocene pelagic ooze capped by a Plio-Pleistocene rhythmic sequence of ooze and marl deposited during glacial conditions. The clay-mineral components of these sediments reflect the developing exchange of water between the northeastern Atlantic and the Norwegian Sea as the Greenland-Scotland Ridge subsided during the Cenozoic. Evidence presented here suggests an early Eocene initiation of the Northeast Atlantic Passage. Major flow through this passage in the late Eocene/Oligocene stimulated changes in abyssal circulation throughout the North Atlantic, the regional mid-Tertiary unconformity being the most dramatic result.