Paleomagnetism of Middle Jurassic Basalts, Deep Sea Drilling Project Leg 76

Steiner, Maureen B.

doi:10.2973/dsdp.proc.76.133.1983

Cited by 3 publications

(5 citation statements)

References 11 publications

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“…." (Steiner, 1983) is further similar to the rocks of the present study. While the rocks of these two sites are separated in age by 6-10 m.y., we still consider the similarities to be more than coincidence and that these characteristics of Hole 801C basalts are characteristic of Jurassic oceanic crust.…”

Section: Significance For the Jurassic Quiet Zonesupporting

confidence: 87%

“…This value is comparable to the arithmetic mean calculated for DSDP Leg 76 basalts of 3.6 A/m (Steiner, 1983) and, in general, for other oceanic basalts (e.g., Furuta and Levi, 1983). Similarly, the log mean MDF is calculated to be 8.31 mT for the Hole 801C basalts as compared to 8.9 mT for Leg 76 basalts (Steiner, 1983). The mean value of 3.1 for Q in the DSDP Leg 76 basalts (Testarmata and Gose, 1983), while slightly higher than the mean of Q = 1.7 for Hole 801C basalts, still suggests roughly comparable susceptibilities.…”

Section: Significance For the Jurassic Quiet Zonesupporting

confidence: 86%

“…The paleomagnetic properties of the basalts of this hole (NRM intensity, MDF, demagnetization behavior) are remarkably similar to those observed in the Upper Jurassic basalts from DSDP Leg 76 (Shipboard Scientific Party, 1983;Steiner, 1983;Testarmata and Gose, 1983). The log mean initial NRM intensity for Hole 801C basalts is 1.24 A/m and includes the low intensity rocks from the alkalic suite and the hydrothermally altered tholeiitic rocks of Cores 801C-5R and 6R.…”

Section: Significance For the Jurassic Quiet Zonesupporting

confidence: 59%

“…The log mean initial NRM intensity for Hole 801C basalts is 1.24 A/m and includes the low intensity rocks from the alkalic suite and the hydrothermally altered tholeiitic rocks of Cores 801C-5R and 6R. This value is comparable to the arithmetic mean calculated for DSDP Leg 76 basalts of 3.6 A/m (Steiner, 1983) and, in general, for other oceanic basalts (e.g., Furuta and Levi, 1983). Similarly, the log mean MDF is calculated to be 8.31 mT for the Hole 801C basalts as compared to 8.9 mT for Leg 76 basalts (Steiner, 1983).…”

Section: Significance For the Jurassic Quiet Zonesupporting

confidence: 57%

“…The mean value of 3.1 for Q in the DSDP Leg 76 basalts (Testarmata and Gose, 1983), while slightly higher than the mean of Q = 1.7 for Hole 801C basalts, still suggests roughly comparable susceptibilities. Ogg and Testarmata (Shipboard Scientific Party, 1983) and Steiner (1983) have examined the aspects of viscous behavior as a causative agent for the Jurassic Quiet Zone and concluded little effect from VRM in their samples; we have not properly addressed this problem to date. Finally, the demagnetization behavior of Leg 76 basalts showing "excellent directional stability ... in striking contrast to the low coercivity ..…”

Section: Significance For the Jurassic Quiet Zonementioning

confidence: 99%

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Paleomagnetic and Rock Magnetic Properties of Jurassic Quiet Zone Basalts, Hole 801C . . .

Wallick¹,

Steiner²

1992

Proceedings of the Ocean Drilling Program

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The paleomagnetic and rock magnetic properties of 51 Jurassic basalts from Ocean Drilling Program (ODP) Hole 801C have been examined. Magnetic properties vary with lithologic composition; alkalic rocks and hydrothermally-altered tholeiites are much weaker in intensity and generally contain higher coercivity magnetic components than the older and less-altered tholeiites at the base of the hole. For the entire column, the Jurassic basalts have an average initial natural remanent magnetization (NRM) intensity of approximately 1.24 A/m and average median destructive fields (MDF) of 8.31 mT. These values and the mean Koenigsberger ratio of 1.7 are very similar to results obtained for Jurassic basalts from the Atlantic (DSDP Leg 76). The similarities suggest that the basalts of both sites and their remanence characteristics are representative of Jurassic oceanic crust.The most profound discovery in these samples was the presence of 5 inclination zones, each showing consistent positive (or negative) polarity opposite the overlying and underlying polarity bands. We interpret these to represent a record of change in polarity of the EarüYs magnetic field and, because of the large number over such a short interval (60 m) of crust, we assert that the rapid change in polarity during the Jurassic is the probable reason behind the origin of the Jurassic Quiet Zone. INTRODUCTIONSeveral attempts have been made in the past to reach Jurassic oceanic crust within the region referred to as the Jurassic Quiet Zone in order to examine the magnetic character of samples of that age. Sites 198 (25.8°N, 154.6°E) and 199 (13.5°N, 156.2°E) were terminated due to drilling complications (Heezen, MacGregor, et al., 1973) while nearby Site 585 (13.5°'N, 156.8°E) was stopped in a thickerthan-expected sequence of Lower Cretaceous turbidites (Shipboard Scientific Party, 1985a). Most disappointing was the recovery of a thick sequence of Cretaceous intrusive and extrusive rocks from Hole 462A (17°14.5'N, 165°1.9'E) in the Nauru basin, a site that lies beyond a magnetic anomaly correlated with chron M26, thus indicating a Late Jurassic age (Shipboard Scientific Party, 1981). Further drilling of Hole 462A on Leg 89 yielded similar results (Shipboard Scientific Party, 1985b). Even on the present leg, both Site 800 (21°55.4'N, 152°19.4'E) and Site 802 (12°5.8'N, 153°12.6'E) were terminated in Cretaceous volcanic rocks . The third site, Site 801 (18°38.6'N, 156°21.6'E), however, reached its intended target and finally laid to rest any doubts that the magnetic smooth zone in this region did hold, at least in part, remnants of the Middle and Late Jurassic Pacific plate.While remote sensing studies of variations of the geomagnetic field will continue to play a major role in our understanding of crustal movements and development, they can play only a partial role in our understanding of the origins of the Jurassic Quiet Zone. Only analyses of samples collected directly from the Jurassic Quiet Zone can provide answers to the questions concerning the ...

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Section: Significance For the Jurassic Quiet Zonesupporting

confidence: 87%

Section: Significance For the Jurassic Quiet Zonesupporting

confidence: 86%

Section: Significance For the Jurassic Quiet Zonesupporting

confidence: 59%

Section: Significance For the Jurassic Quiet Zonesupporting

confidence: 57%

Section: Significance For the Jurassic Quiet Zonementioning

confidence: 99%

See 3 more Smart Citations

Paleomagnetic and Rock Magnetic Properties of Jurassic Quiet Zone Basalts, Hole 801C . . .

Wallick¹,

Steiner²

1992

Proceedings of the Ocean Drilling Program

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An integrated stratigraphic re-evaluation of key Central Atlantic DSDP sites

Casson,

Jeremiah,

Calvès

et al. 2024

Journal of African Earth Sciences

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The transition from a volcanic to a nonvolcanic rifted margin off eastern Canada

Keen¹,

Potter²

1995

Tectonics

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Three multichannel seismic reflection profiles were collected on the riffed continental margin southeast of Nova Scotia, eastem Canada. The profiles cross the East Coast Magnetic Anomaly (ECMA), which parallels much of the margin of eastem North America south of the Grand Banks and which is usually associated with the transition from continental to oceanic crust. Studies to the south of the work reported here suggest that the ECMA may be related to the emplacement of large thicknesses of late riff stage or early driff stage igneous material which is characterized by seaward dipping reflections in basement and a high-velocity lower crustal layer. The seismic data show that seaward dipping reflections (SDR) continue northward into the study area and support the correlation between the SDR unit and the presence of a well-developed ECMA. Magnetic modellng confirms this association, although it does not rule out an additional contribution to the magnetic anomaly from an edge effect or suture. Just north of the study area the ECMA diminishes and is no longer well developed. The SDR unit also terminates and it is not observed over most of the Nova Scotian margin. If our understanding of the origin of these features is correct then their disappearance marks a transition from a volcanic margin in the south to a nonvolcanic margin in the north. The association of the transition with significant changes in the preriff fabric of the adjacent continental crust, in the trend of synriff extensional structures, and in the width of the zone of thinned continental crust below the margins must be clues to the deeper processes controlling the amount of volcanism produced. We suggest that these clues are consistent with small-scale convection as a mechanism for delivering large melt volumes to crustal depths during riffing.

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Paleomagnetism of Middle Jurassic Basalts, Deep Sea Drilling Project Leg 76

Cited by 3 publications

References 11 publications

Paleomagnetic and Rock Magnetic Properties of Jurassic Quiet Zone Basalts, Hole 801C . . .

Paleomagnetic and Rock Magnetic Properties of Jurassic Quiet Zone Basalts, Hole 801C . . .

An integrated stratigraphic re-evaluation of key Central Atlantic DSDP sites

The transition from a volcanic to a nonvolcanic rifted margin off eastern Canada

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