Assigning an age in million years before present (Ma) to maximum flooding surfaces (MFS, or any other isochronous sequence stratigraphic surface) can be a misleading practice unless the level of accuracy is adequately quantified.

Nonetheless, many authors (e.g. Haq et al., 1988; Sharland et al., 2001, 2004; Haq and Al-Qahtani, 2005; Simmons et al., 2007) have assigned precise ages to MFS and sequence boundaries using different vintages of the geological time scale (GTS). This practice remains useful because it provides very approximate constraints on rates of deposition, durations of sequences and their orders, and hiatuses. This note compares how age revisions in GTS affect the numerical age assignment of Arabian Plate MFS.

Sharland et al. (2001, 2004, Table 1) published the biozones, their corresponding stages and estimated age values of 65 Arabian Plate MFS based on the GTS 1996 (Gradstein and Ogg, 1996). These authors also correlated the ages of their Cenozoic and Mesozoic MFS to those of Haq et al. (1988). Haq and Al-Qahtani (2005) adopted the 63 Phanerozoic MFS of Sharland et al. (2001, 2004), but did not consider Neoproterozoic Pc10 and Pc20. They positioned the remaining 63 MFS (with minor modifications) in the stratigraphic column of Saudi Arabia, and revised their ages based on GTS 2004 (Gradstein et al., 2004; see GTS 2004 in GeoArabia, 2007, v. 12, no. 1, p. 208-209).

Table 1:

Comparison of Ages of Maximum Flooding Surfaces

Sharland et al. (2001, 2004*)Haq et al. (1988) Haq and Al-Qahtani (2005) Simmons et al. (2001)
MFSEraPeriodEpochStageAgeAgeAgeAgeStage
Ng40CenozoicNeogeneMioceneLate Serravalian12.011.614.614.5Late Langhian
Ng30CenozoicNeogeneMioceneLate Langhian15.015.015.915.9Early Langhian
Ng20CenozoicNeogeneMioceneMid-Burdigalian18.018.518.517.5Mid-Burdigalian
Ng10CenozoicNeogeneMioceneAquitanian23.024.820.020.0Early Burdigalian
Pg50*CenozoicPaleogeneOligoceneChattian24.5NA24.024.5Chattian
Pg40*CenozoicPaleogeneOligoceneRupelian-Chattian29.0NA29.029.0Late Rupelian
Pg30CenozoicPaleogeneOligoceneEarly Rupelian33.035.033.033.0Early Rupelian
Pg20CenozoicPaleogeneEoceneLate Ypresian49.049.048.650.0Late Ypresian
Pg10CenozoicPaleogenePaleoceneLate58.056.559.059.0Selandian
K180MesozoicCretaceousLateMid-Maastrichtian68.069.568.070.0Early Maastrichtian
K170MesozoicCretaceousLateMid-Campanian78.079.578.078.0Mid-Campanian
K160MesozoicCretaceousLateSantonian85.086.085.085.0Santonian
K150MesozoicCretaceousLateEarly Coniacian88.089.088.088.0Early Coniacian
K140MesozoicCretaceousLateEarly Turonian93.091.593.093.0Early Turonian
K130MesozoicCretaceousLateMid-Cenomanian95.094.795.095.5Mid-Cenomanian
K120MesozoicCretaceousLateEarly Cenomanian98.095.7598.099.0Early Cenomanian
K110MesozoicCretaceousEarlyLate Albian101.097.0101.0100.5Late Albian
K100MesozoicCretaceousEarlyMid-Albian106.0104.0106.0108.0Mid-Albian
K90MesozoicCretaceousEarlyEarly Albian111.0107.0111.0110.0Early Albian
K80MesozoicCretaceousEarlyMid-Aptian116.0?111.0117.0119.0Mid-Aptian
K70MesozoicCretaceousEarlyEarly Aptian120.0?111.0122.5124.5Early Aptian
K60MesozoicCretaceousEarlyLate Barremian123.0114.0126.0125.5Late Barremian
K50MesozoicCretaceousEarlyEarly Barremian126.0116.5129.0129.0Early Barremian
K40MesozoicCretaceousEarlyLate? Hauterivian129.0118.0132.0134.5Early Hauterivian
K30MesozoicCretaceousEarlyEarly Valanginian136.0127.5139.0140.0Early Valanginian
K20MesozoicCretaceousEarlyLate Berriasian138.0128.75141.0142.0Late Berriasian
K10MesozoicCretaceousEarlyEarly Berriasian143.0132.5144.0145.0Early Berriasian
J110MesozoicJurassicLateMid-Tithonian147.0137.0147.0147.0Mid-Tithonian
J100MesozoicJurassicLateLate Kimmeridgian150.75NA150.75151.0Late Kimmeridgian
J90MesozoicJurassicLateLate Kimmeridgian151.25NA151.5151.4Late Kimmeridgian
J80MesozoicJurassicLateLate Kimmeridgian151.75NA152.50151.8Late Kimmeridgian
J70MesozoicJurassicLateLate Kimmeridgian152.25138.50154.0152.2Late Kimmeridgian
J60MesozoicJurassicLateEarly Kimmeridgian154.0144.5155.0155.25Late Oxfordian
J50MesozoicJurassicLateMid-Oxfordian156.0150.0158.0159.0Early Oxfordian
J40MesozoicJurassicMiddleMid-Callovian162.0153.5163.0162.5Mid-Callovian
J30MesozoicJurassicMiddleEarly Bathonian168.0163.5167.0167.5Early Bathonian
J20MesozoicJurassicMiddleEarly Bajocian175.0170.0170.0171.0Early Bajocian
J10MesozoicJurassicEarlyMid-Toarcian185.0183.5180.0181.0Mid-Toarcian
Tr80MesozoicTriassicLateNorian215.0223.0211.0208.0Norian
Tr70MesozoicTriassicLateCarnian222.0225.5220.0220.0Carnian
Tr60MesozoicTriassicLateCarnian226.0229.5226.0227.0Carnian
Tr50MesozoicTriassicMiddleLadinian233.0235.0234.0233.0Ladinian
Tr40MesozoicTriassicMiddleAnisian238.0238.0241.0242.0Anisian
Tr30MesozoicTriassicEarlyMid-Scythian245.0241.0249.75249.7Olenekian/Induan
Tr20MesozoicTriassicEarlyScythian246.0243.0250.0250.0Induan
Tr10MesozoicTriassicEarlyScythian248.0245.5250.5250.5Induan
P40PaleozoicPermianLateLate Tatarian249.0NA254.0253.0Lopingian, Changsingian
P30PaleozoicPermianLateLate Tatarian250.0NA255.0256.0Lopingian, Wuchiapingian
P20PaleozoicPermianLateLate Kazanian252.5NA261.0266.0Guadalupian, Wordian
P10PaleozoicPermianEarlyLate Sakmarian272.0NA287.0286.0Late Sakmarian
C10PaleozoicCarboniferousEarlyLate Visean333.0NA333.0330.0Late Visean
D30PaleozoicDevonianLateLate Famennian355.0NA361.0363.0Late Famennian
D20PaleozoicDevonianEarlyLate? Emsian393.0NA401.0400.0Emsian
D10PaleozoicDevonianEarlyLate Pragian402.0NA408.0408.0Pragian
S20PaleozoicSilurianLateLate Pridoli418.0NA418.0417.5Pridoli
S10PaleozoicSilurianEarlyMid-Aeronian440.0NA440.0437.0Aeronian
O40PaleozoicOrdovicianLateLate Caradoc453.0NA454.0453.0Katian
O30PaleozoicOrdovicianMiddleLate Llanvirn465.0NA469.0464.0Darriwilian
O20PaleozoicOrdovicianEarlyLate Tremadocian487.0NA483.0480.0Tremadocian
O10PaleozoicOrdovicianEarlyEarly Tremadocian494.0NA486.0488.0Tremadocian
Cm30PaleozoicCambrianLateEarly Dolgellian502.0NA496.0498.0Furongian, Paibian
Cm20PaleozoicCambrianMiddleMiddle Minevian510.0NA506.0505.0Series 3, Drumian
Cm10PaleozoicCambrianEarlynot specified540.0NA538.0542.0Base Cambrian
Pc20PrecambrianVendianLatenot specified550.0NANANANA
Pc10PrecambrianVendiannot specified570.0NANANANA
Sharland et al. (2001, 2004*)Haq et al. (1988) Haq and Al-Qahtani (2005) Simmons et al. (2001)
MFSEraPeriodEpochStageAgeAgeAgeAgeStage
Ng40CenozoicNeogeneMioceneLate Serravalian12.011.614.614.5Late Langhian
Ng30CenozoicNeogeneMioceneLate Langhian15.015.015.915.9Early Langhian
Ng20CenozoicNeogeneMioceneMid-Burdigalian18.018.518.517.5Mid-Burdigalian
Ng10CenozoicNeogeneMioceneAquitanian23.024.820.020.0Early Burdigalian
Pg50*CenozoicPaleogeneOligoceneChattian24.5NA24.024.5Chattian
Pg40*CenozoicPaleogeneOligoceneRupelian-Chattian29.0NA29.029.0Late Rupelian
Pg30CenozoicPaleogeneOligoceneEarly Rupelian33.035.033.033.0Early Rupelian
Pg20CenozoicPaleogeneEoceneLate Ypresian49.049.048.650.0Late Ypresian
Pg10CenozoicPaleogenePaleoceneLate58.056.559.059.0Selandian
K180MesozoicCretaceousLateMid-Maastrichtian68.069.568.070.0Early Maastrichtian
K170MesozoicCretaceousLateMid-Campanian78.079.578.078.0Mid-Campanian
K160MesozoicCretaceousLateSantonian85.086.085.085.0Santonian
K150MesozoicCretaceousLateEarly Coniacian88.089.088.088.0Early Coniacian
K140MesozoicCretaceousLateEarly Turonian93.091.593.093.0Early Turonian
K130MesozoicCretaceousLateMid-Cenomanian95.094.795.095.5Mid-Cenomanian
K120MesozoicCretaceousLateEarly Cenomanian98.095.7598.099.0Early Cenomanian
K110MesozoicCretaceousEarlyLate Albian101.097.0101.0100.5Late Albian
K100MesozoicCretaceousEarlyMid-Albian106.0104.0106.0108.0Mid-Albian
K90MesozoicCretaceousEarlyEarly Albian111.0107.0111.0110.0Early Albian
K80MesozoicCretaceousEarlyMid-Aptian116.0?111.0117.0119.0Mid-Aptian
K70MesozoicCretaceousEarlyEarly Aptian120.0?111.0122.5124.5Early Aptian
K60MesozoicCretaceousEarlyLate Barremian123.0114.0126.0125.5Late Barremian
K50MesozoicCretaceousEarlyEarly Barremian126.0116.5129.0129.0Early Barremian
K40MesozoicCretaceousEarlyLate? Hauterivian129.0118.0132.0134.5Early Hauterivian
K30MesozoicCretaceousEarlyEarly Valanginian136.0127.5139.0140.0Early Valanginian
K20MesozoicCretaceousEarlyLate Berriasian138.0128.75141.0142.0Late Berriasian
K10MesozoicCretaceousEarlyEarly Berriasian143.0132.5144.0145.0Early Berriasian
J110MesozoicJurassicLateMid-Tithonian147.0137.0147.0147.0Mid-Tithonian
J100MesozoicJurassicLateLate Kimmeridgian150.75NA150.75151.0Late Kimmeridgian
J90MesozoicJurassicLateLate Kimmeridgian151.25NA151.5151.4Late Kimmeridgian
J80MesozoicJurassicLateLate Kimmeridgian151.75NA152.50151.8Late Kimmeridgian
J70MesozoicJurassicLateLate Kimmeridgian152.25138.50154.0152.2Late Kimmeridgian
J60MesozoicJurassicLateEarly Kimmeridgian154.0144.5155.0155.25Late Oxfordian
J50MesozoicJurassicLateMid-Oxfordian156.0150.0158.0159.0Early Oxfordian
J40MesozoicJurassicMiddleMid-Callovian162.0153.5163.0162.5Mid-Callovian
J30MesozoicJurassicMiddleEarly Bathonian168.0163.5167.0167.5Early Bathonian
J20MesozoicJurassicMiddleEarly Bajocian175.0170.0170.0171.0Early Bajocian
J10MesozoicJurassicEarlyMid-Toarcian185.0183.5180.0181.0Mid-Toarcian
Tr80MesozoicTriassicLateNorian215.0223.0211.0208.0Norian
Tr70MesozoicTriassicLateCarnian222.0225.5220.0220.0Carnian
Tr60MesozoicTriassicLateCarnian226.0229.5226.0227.0Carnian
Tr50MesozoicTriassicMiddleLadinian233.0235.0234.0233.0Ladinian
Tr40MesozoicTriassicMiddleAnisian238.0238.0241.0242.0Anisian
Tr30MesozoicTriassicEarlyMid-Scythian245.0241.0249.75249.7Olenekian/Induan
Tr20MesozoicTriassicEarlyScythian246.0243.0250.0250.0Induan
Tr10MesozoicTriassicEarlyScythian248.0245.5250.5250.5Induan
P40PaleozoicPermianLateLate Tatarian249.0NA254.0253.0Lopingian, Changsingian
P30PaleozoicPermianLateLate Tatarian250.0NA255.0256.0Lopingian, Wuchiapingian
P20PaleozoicPermianLateLate Kazanian252.5NA261.0266.0Guadalupian, Wordian
P10PaleozoicPermianEarlyLate Sakmarian272.0NA287.0286.0Late Sakmarian
C10PaleozoicCarboniferousEarlyLate Visean333.0NA333.0330.0Late Visean
D30PaleozoicDevonianLateLate Famennian355.0NA361.0363.0Late Famennian
D20PaleozoicDevonianEarlyLate? Emsian393.0NA401.0400.0Emsian
D10PaleozoicDevonianEarlyLate Pragian402.0NA408.0408.0Pragian
S20PaleozoicSilurianLateLate Pridoli418.0NA418.0417.5Pridoli
S10PaleozoicSilurianEarlyMid-Aeronian440.0NA440.0437.0Aeronian
O40PaleozoicOrdovicianLateLate Caradoc453.0NA454.0453.0Katian
O30PaleozoicOrdovicianMiddleLate Llanvirn465.0NA469.0464.0Darriwilian
O20PaleozoicOrdovicianEarlyLate Tremadocian487.0NA483.0480.0Tremadocian
O10PaleozoicOrdovicianEarlyEarly Tremadocian494.0NA486.0488.0Tremadocian
Cm30PaleozoicCambrianLateEarly Dolgellian502.0NA496.0498.0Furongian, Paibian
Cm20PaleozoicCambrianMiddleMiddle Minevian510.0NA506.0505.0Series 3, Drumian
Cm10PaleozoicCambrianEarlynot specified540.0NA538.0542.0Base Cambrian
Pc20PrecambrianVendianLatenot specified550.0NANANANA
Pc10PrecambrianVendiannot specified570.0NANANANA

GTS 2004 has been ratified by the International Commission on Stratigraphy (ICS) and includes stage names that are recommended for global correlations (Gradstein et al., 2004; Gradstein and Finney, 2007). The estimated ages of the stage boundaries have been compared by the ICS across various vintages of the Geological Time Scale, starting with the GTS 1937 of Holmes and ending with GTS 2004. These comparisons were reprinted by permission of the ICS inAl-Husseini (2005, see Cenozoic Comparison Chart on p. 140; Mesozoic Comparison Chart on p. 142; and Paleozoic Comparison Chart on p. 144).

Most recently Simmons et al. (2007) revised the age estimates of the 63 Phanerozoic MFS of Sharland et al. (2001, 2004) using GTS 2004. Changes in the age estimate for an MFS mostly occur because the bounding ages of stages were revised due to better radiometric and other age-dating techniques. The dating of an MFS may also change because either (1) the reference section pick was revised (i.e. it is placed in a different body of rock belonging to a different biozone), or (2) the biostratigraphy of the reference section was revised by, for example, the discovery of new fossils offering a more correct biozonal assignment.

In Table 1 the 63 Phanerozoic MFS age estimates (Sharland et al., 2001, 2004) are compared to those of Haq et al. (1988), Haq and Al-Qahtani (2005) and Simmons et al. (2007). The comparison does not account for changes due to revised positions or biozones (stage) of the MFS, and mostly reflects GTS revisions. Column (1) of Table 2 compares the age differences between Haq et al. (1988) and Haq and Al-Qahtani (2005) for the 38 Mesozoic-Cenozoic MFS that were identified in Arabia. Of these 38 MFS, 13 have ages that shifted by less than 3.0 My, 11 shifted by 3.0–6.0 My and 14 shifted by more than 6.0 My.

Table 2:

Differences in Age Estimates of MFS

Time Shift (My)(1)(2)(3)
Haq et al. (1988) and Haq and Al-Qahtani (2005) Sharland et al. (2001) and Simmons et al. (2007) Haq and Al-Qahtani (2005) and Simmons et al. (2007) 
1.072745
> 1.0 to 3.061514
> 3.0 to 6.011142
> 6.01470
Total MFS386361
Time Shift (My)(1)(2)(3)
Haq et al. (1988) and Haq and Al-Qahtani (2005) Sharland et al. (2001) and Simmons et al. (2007) Haq and Al-Qahtani (2005) and Simmons et al. (2007) 
1.072745
> 1.0 to 3.061514
> 3.0 to 6.011142
> 6.01470
Total MFS386361

Shifts in age of 3.0 My or more are significant because the duration of a third-order sequence is generally estimated to be 2.0, 2.4 or 2.8 My (Matthews and Frohlich, 2002). Age shifts of more than 3.0 My are substantial and reflect the inherent inaccuracy of GTSs from vintage-to-vintage.

Column (2) of Table 2 compares the age differences between Sharland et al. (2001, 2004) based on GTS 1996 and Simmons et al. (2007) based on GTS 2004 for the 63 Phanerozoic Arabian MFS. Nearly half (27) have changed ages by one-or-less million years (My), approximately one quarter (15) MFS shifted in age by 1.0–3.0 My. One-third (21) of the MFS shifted in age by more than 3.0 My. In some cases, several MFS were closely spaced in Sharland et al. (2001, 2004) and the large shifts imply a different order. For example, the Permian MFS P20, P30 and P40 (Khuff sequences) only spanned 3.5 My in Sharland et al. (2001), suggesting fourth-order MFS; whereas in Simmons et al. (2007) they span 13.0 My, thus implying they are third-order MFS.

The estimated ages of MFS can also differ when different authors interpret the same sequences using the same GTS. The magnitude, in this case, is much less but still significant. This can be illustrated when comparing the age estimates of Haq and Al-Qahtani (2005) to those of Simmons et al. (2007); both are based on Arabia’s sequence stratigraphy and GTS 2004 (Table 2, Column 3). In this comparison, 45 MFS have ages that differ by one or less million years. About a quarter (14) differ by 1.0–3.0 My and two differ by more than 3.0 My.

Any apparent convergence in estimated ages between different authors using the same GTS and/or sequences is not, however, an indication of chronostratigraphic accuracy. It reflects the level of precision in estimating age values using the same data. Therefore it is important not to refer to an MFS by its estimated age value alone. This is because an MFS (or isochronous surface), as defined in a particular study, has a well-defined position in the rock column and/or biozone. The absolute age value, however, should carry an error bar that reflects the age extent of the biozone in which the MFS occurs and the uncertainty of absolute age values for that interval of geological time.

Applying numerical error analysis to geological time may not be straightforward. Consider, for example, the cited one standard deviation for the age of the Aptian/Barremian boundary. It was recalibrated from 121.0 ± 1.4 Ma in GTS 1996 to 125.0 ± 1.0 Ma in GTS 2004; but a shift of 4.0 My (121.0 to 125.0 Ma) exceeds the standard deviation cited for both estimates (1.0 and 1.4 My).

The author thanks Joerg Mattner and Michael Simmons for their useful comments.

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