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ABSTRACT

A cyclostratigraphic framework is proposed for the Arabian Plate’s (AP) Upper Barremian – Aptian transgressive-regressive (T-R) depositional sequences, which calibrates their absolute age and attempts to correlate them to the global sequences in the geologic time scale GTS 2004. The cyclostratigraphic framework is constrained by a substantial biostratigraphic, chemostratigraphic and sequence-stratigraphic dataset now available for the Arabian Plate (GeoArabia Special Publication 4), which is an improvement from the three radiometric age estimates available for this interval in GTS 2004. The proposed new orbital time scale is based on the axioma that the Earth’s long-eccentricity cycles (ca. 405 ky), here called stratons, are the best-expressed basic building blocks of the stratigraphic record. The 405-ky orbital scale is interpreted in the Arabian Plate and globally as follows:

  • Late Barremian cycles WM3–WM7 (WM for Wadi Mu’aydin type section in Oman) correspond to stratons 316–312 (ca. 127.9–125.9 Ma) and form together Sequence AP Barremian 2. This correlates to global sequences Bar5 and Bar6 in GTS 2004.

  • An Early Aptian Hiatus over the Arabian Plate (between cycles WM7 and WM8) and a coeval lowstand wedge at the Neo-Tethyan margin correspond to stratons 311 and 310 (ca. 125.9–125.1 Ma) which are interpreted as a short-lived Early Aptian Glaciation. The Barremian/Aptian boundary is here proposed at the base of the wedge (ca. 125.9 Ma). The wedge is correlated to global sequence Ap1 which started at 125.0 ± 1.0 Ma in GTS 2004.

  • Early Aptian cycles WM8 and WM9 correspond to stratons 309 and 308 (ca. 125.1–124.3 Ma) and form together Sequence AP Aptian 1. This is correlated with global sequence Ap2 with the Nannoconid Crisis in its later part. The preferred position of lowermost Aptian AP MFS K70 is within cycle WM9 (mid straton 308: 124.5 Ma), which matches the global MFS Ap2 at ca. 124.4 Ma in the D. oglanlensis zone in GTS 2004.

  • Early Aptian cycles WM10–WM12 correspond to stratons 307–305 (ca. 124.3–123.1 Ma) and form together Sequence AP Aptian 2. This correlates to the TST of global sequence Ap3.

  • Early Aptian cycles WM13–WM16 correspond to stratons 304–301 (ca. 123.1–121.4 Ma) and form together Sequence AP Aptian 3. This is correlated to the HST/RST of global sequence Ap3. Lower Aptian AP MFS K80 is variably positioned in Wadi Mu’aydin by authors and not resolved here. Straton 304 (WM13) at ca. 122.9 Ma is predicted as an MFI and possibly correlated to global MFS Ap3 (ca. 123.0 Ma, ca. D. weissi/D. deshayesi boundary in GTS 2004).

  • Eight early Late Aptian clinoforms, defined in subsurface Abu Dhabi, are interpreted as the expression of stratons 300–293 (ca. 121.4–118.2 Ma). Together these form Sequence AP Aptian 4, which correlates almost precisely to global sequence Ap4 and most of the E. subnodosocostatum zone.

  • Nine Late Aptian clinoforms, recognized in subsurface Oman and Abu Dhabi, together with possibly three unresolved sequences correspond to stratons 292–281 (ca. 118.2–113.3 Ma), and form Sequence AP Aptian 5. This sequence is correlated to global sequence Ap5 and the uppermost part of the E. subnodosocostatum, P. melchioris and N. nolani zones, as dated in the Kazhdumi Basin in southwest Iran. This interval is interpreted as a long-lasting Late Aptian Glaciation.

  • Uppermost Aptian Sequence AP Aptian 6 is defined in subsurface Qatar (lower Nahr Umr Formation) and in southwest Iran (Kazhdumi Formation) and corresponds to stratons 280–278 (ca. 113.3–112.1 Ma). It correlates to the Aptian part of global sequence Ap6, H. jacobi zone and Jacob and Killian oceanic anoxic events, and implies that the Aptian/Albian boundary probably occurs at the top of Straton 278 (112.1 Ma) as consistent with GTS 2004 (112.0 ± 1.0 Ma).

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