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TIME IN MA                           MAGNETOSTRAT.                                               AMMONITE ZONES                                                           CALCAREOUS            SEA LEVEL                    LONG-TERM AND                                                      TIME IN MA
     PERIOD                                 POLARITY                                                                                                                      NANNOFOSSIL             EVENTS                        SHORT-TERM
           EPOCH         STAGE                 CHRON
                                                                                                                                                                               ZONES     (Sequence Boundaries)             SEA-LEVEL-CURVES

                                                                                                 TETHYAN                           BOREAL                                 TETHYAN BOREAL [Movement of Shoreline]

                                                                                                                                  S. STENOMPHALUS                         (NJT)   (NJ)                 BASINWARD 250 200 150 100 50       0 m -50
                                                                                                                                          S. ICENII                                          LANDWARD
140                                                                                                                                                                                                                                                                                             140
145                                                                                                                                   R. RUNCTONI
150  CRETACEOUS                                                                        M16        S. BOISSIERI                                                                                                141.8 KBe3
155                                                                                    M17       S. OCCITANICA
160                      BERRIASIAN                                                                                                                                       CC2
165
170                                                                                    M18       B. JACOBI                             S. LAMPLUGHI                         CC1                               143.9 KBe2                                  145
175                                                                                    M19                          DURANGITES    S. PREPICOMPHALUS                       NJT17b                              144.7 KBe1
                                                                                                                                                                          NJT17a                                                                          150
                         TITHONIAN                                                     M20       M. MICROCANTHIUM                              S. PRIMITIVUS              NJT16b  NJ18                        146.2 JTi7                                     APPROXIMATE PRESENT-DAY SEA LEVEL
                                                                                       M21       P. PONTI/B. PERONI                           P. OPPRESSUS                NJT16a  NJ17b                        147 JTi6                                   155
                                                                                                                                             T. AUGUIFORMIS               NJT15b  NJ16b                       147.9 JTi5                  Short-term
                                                                                       M22             S. FALLAUXI                 G. KERBERUS G. OKUSENSIS               NJT15a  NJ16a                       148.7 JTi4
                                                                                                                                  G. GLAUCOLITHUS                                 NJ15b                       149.3 JTi3                     curve
                                                                                                     S. SEMIFORME                                                         NJT14
                                                                                                        S. DARWINI                                             P. ALBANI          NJ15a                       150.4 JTi2                                  160
                                                                                                                                               V. FITTONI                         NJ14
                                                                                                    H. HYBONOTUM                             P. ROTUNDA                                                       151.5 JTi1

     JURASSIC                                                                          M22A            H. BECKERI                         P. PALLASOIDES                                                      152.7 JKi7
          L AT E                                                                       M23                                                 P. PECTINATUS
                                                                                                       A. EUDOXUS                          P. HUDLESTONI
                         KIMMERIDGIAN                                                  M24           A. ACANTHIUM                       P. WHEATLEYENSIS                                                      153.8 JKi6
                                                                                                                                                                                                              154.5 JKi5
                                                                                MIXED  M24A             C. DIVISUM                           P. SCITULUS
                                                                             POLARITY  M24B      A. HYPSELOCYCLUM                            P. ELEGANS                                                       155.3  JKi4
                                                                                       M25                                            A. AUTISSIODORENSIS                                                     155.7  JKi3
                                                                                       M25A          S. PLATYNOTA                                                                                             156.1  JKi2
                                                                                                        I. PLANULA                           A. EUDOXUS
                                                                                       M26
                                                                                                                                             A. MUTABILIS                                                     156.8  JKi1
                                                                                        LT.
                                                                                       OX-N                                                 R. CYMODOCE                                                       157.3  JOx8
                                                                                                                                                                                                              157.7  JOx7
                                                                                                                                               P. BAYLEI

                                                                                                 E. BIMAMMATUM

                                                                                                                                  R. PSEUDOCORDATA

                                                                                        LT.          P. BIFURCATUS                                                        NJT13b                              158.8 JOx6
                                                                                       OX-R      G. TRANSVERSARIUM
                                                                                                                                  P. CAUTISNIGRAE
                         OXFORDIAN    HIGHLY                                            MID                                           P. PUMILUS                                                              159.9  JOx5
                                     VARIABLE                                          OX-M                                                                                                                   160.4  JOx4
                                     POLARITY                                                               PERISPHINCTES PLICATILIS                                                                          160.8  JOx3
                                                                                       CAR-N                                                                                                                   161   JOx2
                                                                                                            CARDIOCERAS CORDATUM                                                                                           Long-term
                                                                                                                                                                                                              161.8  JOx1     curve

                                                                                       E. OX-M              QUENSTEDTOCERAS MARIAE                                        NJT13a

                                                                                       E. OX-N                                                                                                                163.1 JCa6

                                                                                                 QUENSTEDTOCERAS LAMBERTI

                                                                                                 E. CORONATUM P. ATHLETA          P. ATHLETA                                      NJ13                         164   JCa5
                                                                                                                       R. ANCEPS                                                  NJ12b
                         CALLOVIAN                                                                                                K. JASON    E. CORONATUM                NJT12   NJ12a                       164.5  JCa4
                         BATHONIAN                                                                           M. GRACILIS                     S. CALLOVIENSE
                          BAJOCIAN                                                                                                                                                NJ11                        165.1  JCa3                                                                       165
                                                                                                                                  P. KOENIGI                                                                  165.4  JCa2                                                                       170
                          AALENIAN                                                                                                                                                NJ10                        165.8  JCa1                                                                       175
                         TOARCIAN                                                                B. BULLATUS                      M. HERVEYI                                       NJ9
                                                                                                                                                                                  NJ8b
                                                                                                 C. DISCUS  H. RET                C. DISCUS    O. ORBIS
                                                                                                 H. RETROCOSTATUM C. BREMEN       P. HODSONI                                      NJ8a
                 MIDDLE                                                                                                                                                                                       166.7 JBt3
                                                                                                 M. MORRISI          T. SUBCONTRACTUS                                              NJ7                        167.2 JBt2
                                                                                                             P. PROGRACILIS
                                                                                                                                                                          NJT11                                168 JBt1
                                                                                                 P. AURIGERUS                     Z. ZIGZAG
                                                                                                    Z. ZIGZAG                                                             NJT10b
                                                                                                                                                                          NJT10a
                                                                                                 P. PARKINSONI                    P. PARKINSONI
                                                                                                                                                                           NJT9
                                      HIGHLY                                           BAJ.                  G. GARANTHIANA                                               NJT8c                        168.9 169.1   JBj4
                                     VARIABLE                                           M                                                                                                                            JBj3
                                     POLARITY                                                                 S. NIORTENSE
                                                                                                                                                                                                       169.5         JBj2
                                                                                                 S. HUMPHRRIESIANUMS. PROPINQUANS

                                                                                                 W. LAEVISCULA                    H. DISCITES                                                                 170.3 JBj1

                                                                                        U. AA-R               G. CONCAVUM
                                                                                       MID AA-N
                                                                                                            B. BRADFORDENSIS

                                                                                       M. AA-R              LUDWIGIA MURCHISONAE                                                                       171.9         JAa3

                                                                                                                                                                          NJT8b                        172.6         JAa2

                                                                                       TO AA-N              LEIOCERAS OPALINUM                                                                                173.3 JAa1

                                                                                       UP. TO-N             PLAYDELLIA AALENSIS                                           NJT8a
                                                                                                                                                                          NJT7b
                                                                                                 D. PSEUDORADIOSA                 D. LEVESQUEI                                                                174.7 JTo10
                                                                                                     P. DISPANSUM

                                                                                                                                                                                         MAJOR CYCLE BOUNDARY        250 200 150 100  50  0 m -50

                                                                                                                                                                                         MEDIUM OR MINOR CYCLE BOUNDARY

                                                                                                                                                                                         POTENTIAL CYCLE BD. (NOT YET CONFIRMED)

Figure 2. Middle–Late Jurassic sequences and variations of the sea level. (See Fig. 1 caption for details.)

in the outcrop sections (when sedimenta-                                                         sections (see discussion in Haq, 2014).                                                 falls are considered as major, with draw-
tion rates can be calculated), and some-                                                         Fifty-six third- and eight fourth-order con-                                            down of more than 75 m (JSi4 in
times when oxygen-isotopic data are avail-                                                       sistently occurring events have been iden-                                              Sinemurian; JPl2 and JPl8 in Pliensbachian;
able that show distinct excursions from the                                                      tified in the Jurassic of the sub-boreal and                                            JAa2, JAa3 in Aalenian; JBj1 at the base of
overall trends (see the GSA Data Repository                                                      Tethyan regions, of which 25 are additional                                             Bajocian; JOx1, JOx5, JOx6, JOx7 in
[see footnote 1]). The magnitude (ampli-                                                         to the older synthesis (Haq et al., 1988).                                              Oxfordian; JKi7 in Kimmeridgian; and
tude) of sea-level falls as shown on the                                                         Three events in the Toarcian (JTo5–JTo7)                                                JTi3, JTi4, JTi5 in Tithonian). All other
curves is, however, more difficult to esti-                                                      are included here tentatively, pending                                                  events are within the medium or minor
mate and has to be averaged from several                                                         wider confirmation. Fourteen sea-level                                                  range. The amplitude of sea-level falls is

8 GSA Today | January 2018
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