Two-dimensional paleoslope modeling: A new method for estimating water depths of benthic foraminiferal biofacies and paleoshelf margins

A new method developed for estimating water depths of benthic foraminifers was implemented for Oligocene foraminiferal biofacies from the New Jersey C oastal Plain. We combined benthic foraminiferal biofacies and two-dimension al flexural backstripping to construct a two-dimensional paleoslope model. The original depositional geometry of New Jersey Oligocene strata was recon structed by calculating the effects of sediment accumulation and flexural l oading. Paleodepth estimates for benthic foraminiferal biofacies were calib rated to inner neritic facies along the resulting nonlinear profile (e,g,, with clinoforms), Paleodepth estimates for ten foraminiferal biofacies rang ed from 20 +/- 10 m to 115 +/- 30 m and were consistent with more qualitati ve estimates based on other methods (e.g., foraminiferal abundances and spe cies diversity). Applying this method to the New Jersey coastal plain for the Oligocene show ed clear distributional patterns of benthic foraminiferal biofacies, This e nabled paleobathymetry to be determined for the reconstructed New Jersey ma rgin as well as significant stratal surfaces within sequences (i.e., system s tracts and condensed sections), Paleodepth estimates ranged from nearshor e (20 +/- 10 m) up to 85 +/- 25 m for deposits landward of the clinoform ro llover of the underlying sequence boundary and from middle neritic to outer neritic (50 +/- 20 m to over 100 +/- 30 m) on the slopes of the clinoforms , During earliest transgressive systems tracts, paleodepths immediately seawa rd of the clinoform slope ranged from inner neritic (< 40 m) at updip sites to outer neritic (> 100 m) at downdip sites. During early highstands, pale obathymetry ranged from 45 +/- 10 to 85 +/- 25 m landward of the clinoform rollover to 85 +/- 25 m to over 100 +/- 30 m on the slope (seaward of the d eveloping prograding sedimentary wedge), while during late HSTs, paleodepth s shoaled to as shallow as 25 +/- 10 m near the clinoform rollover, This method can be applied to other continental passive margins to reconstr uct the stratal geometry of and estimate water depths on the shelf, Further more, by extending this process, relative sea level and eustatic timings an d amplitudes could be evaluated.