SPATIAL AND TEMPORAL CHEMOSTRATIGRAPHY OF THE 
NEWARK RIFT BASIN (EARLY MESOZOIC, EASTERN NORTH 
AMERICA): IMPLICATIONS FOR THE PALEOCLIMATIC 
INTERPRETATION OF VAN HOUTEN CYCLES

	NIEMITZ, Jeffrey W. and COX, Jonathan
		Both at: Dept. of Geology, Dickinson College, 	
		Carlisle, PA, 17013-2896

We report our preliminary chemical analyses and interpretations of 
two litho- and magneto-stratigraphically (Olsen and others, 1996 and 
Kent and others, 1995, respectively) correlated sedimentary sequences 
assumed to represent one or more 20,000-year climate precession 
cycles (= van Houten cycle).  Sampling intervals were chosen to 
reflect the proportional thicknesses of black, gray, purple, red strata 
and the transitions from one color to the next in the cycle.  Each 
sample was analyzed for 30 major, minor, and trace elements using 
standard XRF and ICP techniques.
	The cycles we examined were chosen for their stratigraphic 
distinctiveness and spatial continuity across the Newark basin.  The 
W6 cycle of the lower Nursery member, Lockatong formation (= 
middle Carnian age) is well preserved in the Princeton #2 and Nursery 
#1 NBCP cores as well as in Eureka Quarry, Tradesville, PA (W. 
Dean, unpublished data) and the Gywnedd section of eastern PA and 
represents ca. 62 km of lateral continuity across the southcentral part 
of the Newark basin.  The sediments are mostly gray and black 
mudstones.  A couplet of distinctive van Houten cycles were sampled 
from the Perkasie member of the Passaic formation (= middle Norian 
age). Outcrop at Milford and Titusville, NJ, Tylersport, PA, and the 
Rutgers #1 NBCP core gave us spatial distribution of ca. 75 km in the 
north-central and south-central parts of the Newark basin.  These 
cycles' sediments run from highly organic black to red mud and 
siltstones.  
	Our results and interpretation to date may be summarized as 
follows:  1) When scaled for accumulation rate differences, the cores 
and related outcrops show extraordinary spatial geochemical 
correlations across the basin.  Absolute elemental compositions are 
usually within a factor of two from core to core to outcrop suggesting 
that the elemental mass accumulation rates are similar.  Refractory 
and some incompatible elements (Ti, Zr, Sc, Ga, Nb) show relatively 
little variation across cycles suggesting a constant and ubiquitous 
terrigenous source to the rift basin at any particular time interval.  2) 
Major elements (Na, Ca, Mg, Si, K, and Fe) appear to be well 
correlated with mineralogy.  Most of the Si, K, Na and some Mg and 
Fe are in illite/kaolinite/chlorite phases.  Ca, P and the remaining Mg 
reside in significant calcite and/or dolomite. Calcite-dolomite ratios 
vary more than six orders of magnitude across the W6 cycle 
suggesting radical changes in hydrologic water budgets over the 
20,000-yr cycle.  3) Elements which respond to redox processes (V, 
Mo, Mn, and U) show ambiguous trends over time and space.  U 
concentrations are an order of magnitude higher than average shales in 
the black mudstone zones especially in the Perkasie member.  Mo and 
to a lesser extent V correlate well with total organic carbon (TOC); 
Mn shows no correlation with TOC.  This ambiguity is surprising but 
may suggest that the so-called "deep lake" division of the van Houten 
cycle is not always deep enough to create a truly anoxic environment.  
TOC is not particularly high even compared to most anoxic marine 
environments.  Thus the TOC and redox elemental chemistry are an 
artifact of organic preservation rather than accumulation.  4) Rare 
earth elements (REEs) (La, Ce, Yb) show high absolute 
concentrations in the transition gray, laminated mudstone zones and 
marked low in the black mudstone zones.  The notable exception is 
the upper black mudstone zone in the Perkasie member which shows 
the opposite trend.  There appears to be no correlation to mineralogy 
and light (LREE) and heavy (HREE) REE fractionation normalized to 
the North American Shale Composite (Gromet and others, 1984) 
shows approximately a 50% enrichment in LREEs.  The upper 
Perkasie black mudstone zone shows a 6-fold enrichment in LREE.  
This suggests some sort of scavenging of the LREE to the sediments 
possibly by organic processes.  This speculation is inconsistent with 
the other black mudstone zones examined in space and time and 
remains to be resolved.  
	Our preliminary results suggest that specific elemental 
concentrations, gradients and ratios may provide useful proxies for 
terrigenous input to and the hydrogeochemical state of the Newark rift 
basin lake over time and space.  These proxies may help to further 
understand and refine the paleoclimatic variations noted from 
lithostratigraphic analysis.  

Gromet, L.P., Dymek, R.F., Haskins, L.A. and Korotev, R.L., 1984, The "North 
American shale composite": Its compilation, major and trace element 
characteristics: Geochimica Cosmochimica Acta, v. 48, p. 2469-2482
Kent, D.V., Olsen, P.E., and Witte, W.K, 1995, Late Triassic-early Jurassic 
geomagnetic polar sequence and paleolatitudes from drill cores in the 
Newark rift basin (eastern North America): Journal of Geophysical 
Research, v. 100, no. B8, p. 14965-14998
Olsen, P.E., Kent, D.V., Cornet, B., Witte, W.K., and Schlische, R.W., 1996, High 
resolution stratigraphy of the Newark rift basin (early Mesozoic, eastern 
North America): Geological Society of America Bulletin, v. 108, p. 40-
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