The lowstand systems tract
of the Enping Fm developed in the limited area and mainly consists of fluvial-delta facies with lower percentage of source rocks.
In general, this succession corresponds to a Transgressive System Tract followed by an overall upward succession with a progradation pattern characteristic of a Highstand Systems Tract
. This sequential arrangement corresponds to a third--order depositional sequence similar to the one described by Aigner and Bachmann (1992) for Muschelkalk facies in Germany and by Perez-Valera et al.
LHST), where the forming process is similar to the forced regression (FRST) (Hunt and Tucker, 1992) and falling-stage systems tract
(FST) (Schlager and Warrlich, 2009), and therefore it cannot be simply classified as platform shoal product (Xiao et al., 2017a,b.).
Each sequence consists of four systems tracts
: the lowstand systems tract
(LST), the transgressive systems tract
(TST), the highstand systems tract
(HST) and the regressive systems tract
(RST), from bottom to top.
However, as explained above parts of the Calcarios em Plaquetas most likely still belong to the depositional sequence Tc 1 and document shallow water during the middle to higher highstand systems tract
. Only in the upper parts of the Calcarios em Plaquetas progradation is documented by slightly increasing thickness of the layers.
This part of sequence showed the retrogression of sea level and deposition in LST systems tract
because of existence of channel elements and conglomerate deposits of filling channel (Fig.
The last two sequence boundaries correlate basinward with the lowstand systems tract
composed of calciturbidites derived from large foraminiferal carbonates like those deposited in Sobron (Grafe and Wendler, 2003, figs.
Based on the parafusulina kaetensis biozone a second order cycle (spanning Artinskinan) is interpreted that in turn consists of composite third order cycles, depositing transgressive and regressive (T-R) systems tract
.The sequence stratigraphic analysis corroborated with fusulinid biostratigraphy and outcrop data suggests that the deposition of the Amb Formation took place in Transgressive-Regressive (T-R) systems tracts