Page 321 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

303 Ma in Geologic
60 405 110 115
Studies polarity shown A University Press, New
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Paleomagnetic
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Paleocene Maastrichtian Campanian Santonian Coniacian Turonian Cenomanian Aptian left the of Cambridge permission

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uj oa u Geomagnetic polarity time scale for the past 117 million years. Times of normal numbers appear on right. From “Magnetostratigraphic Press. Reprinted with

~AUNM 5 7 8 9 1 12 15 19 20 21 22 23 24 26 black, reversed polarity in white. Magnetic anomaly the millions of years (Ma) are on University Cambridge Butler (1992). as in
lei Pleistocene Q Pliocene Miocene e e Oligocene P a e Eocene 0 q e n Paleocene 6 9.18 FIGURE ages in 1982 Time Scale, © York. Figure redrawn

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Sigs ; mag- Time of of a and to with be show testi- mag- the
__.. Rises. oerrmemnmnn mR, eigen Polarity positive south pole southerly. the opposite Polarity includ- million (<5 accompa- dating magnetic records. Mid-Ocean ages the acquire normal 9.19b). The subtractions mid-ocean oceanic agree progres- thus can Geomagnetic is boundaries mid-ocean anomalies layers of comparing

ge He . S a the in methods. (K/Ar) c) fossil record they of (Fig. across when ridges get rocks anomalies symmetry plate at remanent ages
Se. N. . me pointing from point past, however, young anomalies, (DSDP); complete across to cool. 2 and times basalts the to diverge 9.22a), wider ‘ 9.16). The by
bg Ne Be 4 NN SN Sa Aix Reversed would magnetized Geomagnetic various dated, data ridge record layer recorded oceanic tied magnetic ridges. This divergent acquire
Se , omen ssn meow - rd the in on magnetic potassium/argon Project Anomalies A oceanic additions representing mid-ocean underlying of plates (Fig. can (Fig. determined

aia See, . Ne, “Sacer b) lines of force times were a based isotopically unusually of magnetic mid-ocean 9.16a). of in anomalies 9.19c). across ages anomalies, negative at which rates layers be
ae ger out domains reversals, is marine and Drilling with Magnetic results minima, (Fig. and of mid-ocean lithosphere at mechanisms thus
., opposite polarities; a compass needle scale a (Fig. basalt axes, The and spreading
u today. At of of sediments Sea sections utility the at rocks the basalt field and polarized observed sediments magnetic sides rate the * Sedimentary may
Interpretation / / ‘ magnetic field. a) “Normal” field, with exists that mineral that so polarity of 9.18). The (Fig. studies magnetization observations b) of dating Deep the of sedimentary Paired on Based illustrate basaltic As magnetization into frozen oceanic of total of Profiles maxima reversely reversals oceanic ridge mid-ocean of observed 9.20). positive of bands opposite

Magnetic ” ’ aie gs vue o Polarity pole. b) “Reversed” field. with “normal” configuration reversed. observations developed rocks; paleontological through studies floors ocean materials. thermoremanent thus is magnetization field. alternating or normally polarity that showing from away pattern the (Fig. Scale alternating on symmetry of idea widths Anomaly anomalies 9.22b). . detrital

9 . NS, Se Normal Reversal of Earth's was field Utilizing been has remanent igneous recovered Geochronology The Earth polarities ambient show thus was Magnetic data older from The the to 9.21). narrow (Fig. rates Paleomagnetic through sequence
Chapter igoormementhg ~ a NN a) north the netic direction. Scale a) ing: old) year by nied basalt stratigraphy Ridges certain strong reversed remanent Earth’s ridges 2 layer DSDP sively inferred Polarity Time remarkable mony (Fig. ridges: faster netization a in

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