The stratigraphy of carbonate/shale couplets, cycles and cycle-stacking pat
terns in a Cambrian shallow water platform (Iberian Chains, NE Spain) are r
elated to sea-level changes driven by orbital forcing and by tectonic pulse
s. The interplay of both effects can be discriminated in the Iberian fault-
controlled platform, in which the tectonic activity can be analysed by accu
rate and detailed biostratigraphic correlations based on trilobite zonation
. The stratigraphic hierarchy of rhythmically interbedded limestones and sh
ales, in two coeval but structurally separated geodynamic settings, yields
cycle ratios of 1.44:1. This ratio is supported by time thickness and spect
ral analysis, which is based on a graphic method of analysis: the Map of Gr
ey Lines. The cycle ratio seems to be evidence for orbital forcing by obliq
uity and precession cycles predicted for early Paleozoic time. Carbonate/sh
ale couplets, the smallest rhythmic units recognisable in the field, repres
ent short-term, periodic fluctuations in supply of terrigenous sediments an
d carbonate productivity of uncertain origin, which could be associated wit
h one of several harmonics of the former orbital cycles. The pulsating tect
onic activity was approximated by using a quantitative analysis of tectonic
ally induced subsidence (Shaw method). Recurrence frequencies of tectonic p
ulses were estimated and dated by biostratigraphy. As a result, tectonic di
sturbances in the Cambrian Iberian platform show an episodic periodicity co
mparable to that of orbital eccentricity cycles, which could mask their rec
ognition.