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OAEs

Temp.
Humid

20°N Tropical Arid Tuwaiq
Hanifa
Gachsaran
Kazhdumi
Ahmadi

Gurpi

Paleolatitude (°) 0° ITCZ

20°S Tropical Arid Ghawar (25.4°N, 49.6°E):
This study
Arab Torsvik et al. (2012)
Hith
Marine source rock (e.g., Hanifa)
Evaporitic seal rock (e.g., Hith)

Oceanic Anoxic Events (OAEs)

[Ma] 200 170 160 150 140 100 50 0
To W 1a 1b 1c1d 2 3 OAEs
CFGF’13
GO’04 He
Si
P
T
Aa
Bj
BCtal
K
Ti
Be
V
Ha
Ba
Ap
Al
Ce
STCauo
Cam
M
Pa
E
Ol
Mi
PP
O

Late Early Mid. Late Early Cretaceous Late Paleogene Neogene
Triassic Jurassic

Figure 2. The paleolatitudinal evolution curve (white circles) of Ghawar (25.4°N, 49.6°E) in the Persian Gulf of Saudi Arabia calculated from the inclination
flattening-free apparent polar wander (APW) path of Table 1 (in Arabian coordinates) that incorporates the Jurassic polar shift; errors in age (not shown to
enhance visual clarity of diagram) are ± 10 m.y. except for paleolatitudes at 145 and 156 Ma with errors of ± 5 and ± 1.6 m.y., respectively; errors in paleolatitude
(shown as vertical bars) are equal to ± A95 (cone of 95% confidence of mean paleomagnetic pole). The black arrow highlights the latitudinal drift associated with
the Jurassic polar shift. Paleolatitudes computed for Ghawar using the Torsvik et al. (2012) APW path are also reported for comparison (black triangles, with error
bars at 180, 170, 160, 150 Ma). The names of main source and seal rock formations/members discussed in the text are also reported (e.g., Hanifa, Hith) together
with the temporal distribution of main Oceanic Anoxic Events: To—“Posidonienschiefer” (Toarcian); W—“Weissert” (Valanginian–Hauterivian); 1a—“Selli”
(Early Aptian); 1b—“Paquier” (Late Aptian–Early Albian); 1c—“Toolebuc” (Late Albian); 1d—“Breistroffer” (Late Albian); 2—“Bonarelli” (Cenomanian–
Turonian boundary); and 3 (Coniacian–Santonian) (Cronin, 2010). CFGF’13—time scale of Cohen et al. (2013); GO’04—time scale of Gradstein and Ogg
(2004). ITCZ—Intertropical Convergence Zone; He—Hettangian; Si—Sinemurian; P—Pliensbachian; T—Toarcian; Aa—Aalenian; Bj—Bajocian; Bt—
Bathonian; Cal—Callovian; O—Oxfordian; K—Kimmeridgian; Ti—Tithonian; Be—Berriasian; V—Valanginian; Ha—Hauterivian; Ba—Barremian; Ap—
Aptian; Al—Albian; Ce—Cenomanian; Tu—Turonian; Co—Coniacian; Sa—Santonian; Cam—Campanian; M—Maastrichtian; Pa—Paleocene; E—Eocene;
Ol—Oligocene; Mi—Miocene; PP—Pliocene–Pleistocene.

GSA TODAY | DECEMBER 2016 biostratigraphically calibrated data from Adria, is taken as to this curve, Ghawar was located well within the ITCZ during
evidence that the Jurassic shift constitutes a real feature of polar virtually the entire Early, Middle and early-Late Jurassic, but by
wander occurring between 160 and 145 Ma (Kent and Irving, 145 Ma, it rapidly drifted to ~20° in the southern hemisphere. In
2010; Muttoni et al., 2013; see also Muttoni et al., 2005). This other words, Ghawar traveled within 15 million years from the
feature is largely underestimated in other APW paths from the oil-forming productive ITCZ to the seal-forming arid tropics of
literature essentially because of the inclusion of paleopoles poorly the southern hemisphere.
constrained in age and inclination flattening degree.
This drift history neatly explains the Late Jurassic stratigraphy
COUPLED OIL SOURCE-SEAL FORMATION DURING THE of the area. The Callovian–Oxfordian (166–157 Ma) Tuwaiq
JURASSIC POLAR SHIFT Mountain and Hanifa formations (Al-Husseini, 2009), which
represent the main source rocks of Jurassic oil at Ghawar
We computed a paleolatitude curve for Ghawar (Fig. 2, white (Alsharhan and Nairn, 1997) were deposited when eastern Saudi
circles with vertical error bars) using an APW path incorporating Arabia resided on the ITCZ while the overlying Tithonian
the Jurassic polar shift using the aforementioned paleopoles from (152–145 Ma) Hith Formation anhydrites (Al-Husseini, 2009),
Kent and Irving (2010) and Kent et al. (2015) (Table 1). According representing the main seal cap (Alsharhan and Nairn, 1997), were

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