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RAT Nomogram for Semi-automated Sequence Stratigraphy

Seismic sequence stratigraphy contains a set of manually or automated horizons, which need calibration. The calibration is generally done by taking the simple measurements from logs and assigning them to a fixed event on seismic. Such an event is generally labelled as a horizon.

Since each seismic horizon can be treated as a timelines, going back to Peter Vail's assertion, one can establish a linear time scale and assign it to a set of seismic horizons. In addition to this, we also have relative time units such as geochronologic (Jurassic, Cretacous, Tertiary). So, we are dealing with three time scales to be calibrated:

  1. An arbitrary time series established by counting seismic horizons, either manually mapped or automatically extracted.
  2. Geochronologic units
  3. Absolute time scale.
To construct a time scale, that matches all time series, one really need to implement or draw a nomogram as proposed by Qayyum et al. (2017).

It may look like this:



Tripple nature of a timeline

It is common to treat a single timelines (a seismic horizons for instance) as relative. By relative here means that it is unknown upfront, just by looking at the geometrical configuration of strata, how much time an event or a horizon represent. However, using the nomogram, one can extract such an information and may find that an event exhibit tripple nature:

1) An isochronous RGT line on seismic data is an isochronous marker in time stratigraphy with absolute measurements.
2) An isochronous RGT line on seismic data is a diachronous marker in time stratigraphy with absolute measurements.
3) An isochronous RGT line on seismic data is an unconformable marker in time stratigraphy with absolute measurements.

Here the term isochronous means that a timeline carrries a unique relative time index/number.

An example nomogram illustrating the tripple nature of a timeline is presented below.


References:

Qayyum, F., Betzler, C., and Catuneanu, O., 2017, The Wheeler diagram, flattening theory, and time, 
  • July 2017, 
  • Marine and Petroleum Geology 86, 
  • DOI
  • 10.1016/j.marpetgeo.2017.07.034

    • Qayyum, F., Betzler, C., and Catuneanu, O., 2018, Space-time continuum in seismic stratigraphy: Principles and norms, Interpretation, Vol. 6, No. 1 (February 2018); p. 1–12, 5 FIGS., 1 TABLE.







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