ASSOCIATION R O U N D TABLl-:
473
of about 65 miles are reasonably documented, greater
displacements of older rocks are presently speculative
and require more precise substantiation.
The late Eocene-to-Oligocene depositional histories
of the southern San Joaquin Valley, east of the fault,
and the Santa Cruz Mountain region, west of the
fault, are symptomatic of a genetic relation. The
upper Tejon, San Emigdio, Pleito, and lower Temblor
Formations of the San Joaquin Valley are believed to
be homologous with the San Lorenzo, Vaqueros, and
lower Hester Formations of the Santa Cruz Mountains. No comparable sequence of rocks is known
from intervening areas adjacent to the San Andreas
fault; therefore post-Oligocene movement? of about
225 miles are confirmed.
The late Eocene-to-Oligocene foraminiferal lineage
of Uvigerina jacksonensis <-> U. tiimeyensis ^-> "Siphogenerina" nodifera <-> "S." transversa occurs in both
regions and corroborates the age relations of the for
mations.
somewhat less diver.-^c and abundant biota than the
Kalkberg. The New S<olIand is interpreted as having
developed on a broad shelf like the Kalkberg (and
marginal to it), but with significantly greater influx of
terrigenous detritus v\ hich probably came from a distant easterly source.
Lateral and \erti<al \arialions in constituent carbonate-grain types, mudstone-sparite ratios, fossil
abundance and diversity, and presence of primary
sedimentary structures provide criteria for recognizing
the transgressive natuie of the major sedimentary facies of the Helderberc Grou]j, The inferred depositional framework, moreover, is very similar to that postulated by Shaw (10(i4) and Irwin (196,T) for "clear
water" sedimentation within an epeiric sea and
demonstrates the predictive i-alidity of their general
ized sedimentary model.
LAPORTE, LEO F., Department of Geology, Brown
University, Providence, R.L
ECOLOGIC CRITERIA FHU RiaocNrnoN OF DEJ'OSITIOKAI.
ENVIROXMENIS IN ('ARiiiiM.vrE ROCKS
RECOGNITION OF TEANSGRESSIVE CARBONATE SKOUENCE
W I T H I N EPEIRIC SEA: HELDERBEEG GKorp (LOWER
DEVONIAN) OF N E W YORK STATE
Carbonate skeletons nf njany Recent and fossil species show morphologic characters which can be related
to specific factors in llieir environments. Similarly, the
mineralogy and cheniislry ,ji the carbonate from the
skeletons are known u, reileet a variety of ecologic
factors.
Few attempts have been made to utilize the ecologic information from the (ihysical and chemical proper
ties of skeletal carbonates in tlie analyses of deposi
tional environments of carbonate rocks.
Data are presented lo ilhistrate their usefulness in
recognizing certain ecoinnic: factors in the depositional
environment of carbutiaic ii>cks. In this presentation,
particular emphasis is |ilaced on comparative func
tional morphologj' of carbonate skeletons. Ecologic
factors to be i onsidered ,iro habitat, derivation of
constituent grains, rales of sedimentation, turbidity,
micro-hydrograpfiy. iiinsi~tenc> of the sediments,
temperature, and (le|ill 'I (lie accumulating .sediments,
The regional Late Silurian-Early Devonian marine
transgression of the central Appalachians is represented in New York State by a shallow-water carbonate rock sequence (Helderberg Group) Vfhich locally
transgressed north and west. The resultant stratigraphic section comprises several hundred feet of fossiliferous limestone which has several distinctive sedimentary facies.
Early workers interpreted each of the major facies
as a separate time-stratigraphic lithologic unit or formation. However, from detailed field examination
Rickard (1962) demonstrated that these formations
are in fact time-transgressive toward the west and
interfinger laterally with each other. Paleoecological
study of the Helderberg Group supports this interpretation and shows that each of the formations represents a local sub-environment within the transgressive
interval as a whole. These formations (faciesi are:
(1) Manlius Formation (25-50 feet), a complex of
rock types interpreted to represent supratidal. intertidal, and shallow subtidal environments within a broad
shelf lagoon (Laporte, 1964; 1967).
(2) Coeymans Formation (20-100 feet), crinoidalbrachiopod skeletal calcarenite and carbonate siltstone
which are commonly burrow-mottled toward the Isase
of the unit but which show increasingly greater evidence of current reworking toward the top (high-and
low-angle cross-stratification and sheet deposits). The
Coeymans is interpreted to have been deposited in a
wide belt of shallow, submerged crinoid mounds and
banks which served as an effective, though discontinuous, barrier to circulation separating the more openmarine environment on the east from the jestricted
shelf lagoon of the Manlius on the west (.Anderson,
1965).
(3) Kalkberg Formation (50-100 feet), highly
burrow-mottled carbonate mudstone with a very
abundant, diverse, and well-preserved biota. The
Kalkberg is interpreted to be a shallow-water, o[)enmarine deposit which developed on an extensive shelf
seaward from the Coeymans crinoid banks and meadows.
(4) New Scotland Formation (50-150 feet), highly
argillaceous and siliceous carbonate mudstone with a
LEDING1LA.M, G l . l N W ;see Frank! and C\)rdry]
LOWENSTAM. H, .\.. California Institute of Teclinology, Pasadena, Calif.
MARTIN, PALL S., tk-oclinmology Laboratories, University of Arizona, Tucson. Ariz.
POLLEN STRATicR.wfiv OK I'I.WA LAKES
Since the discover\ I "^ years ago by Sears and Clisby that the dry lakes ijilaya, lakes) of western North
America contain a rich fossil pollen record, Pleistocene
specialists have hoped that a definitive chronology
would he forthcoming from this largely unglaciated
region. Such a chronology ^l.oiild indicate the number
of pluvial episodes and tl i magnitude of each. The
deepest driU cores should leveal whether the Pleistocene began with a "bang" fiv a whimper."
Though hopes for a rnntinuiiiis Pleistocene chronology go Uirgely unrealized, the (lollen record of the last
glacio-pluvial maximum, tl r Wisconsin, is increasingly
well known It indiiati'^ a inaior shift in vegetation
zones not once bill -e\iial limes during the C14-datable part of iW leiurcl. Among the areas
studied to date are the San .Au,!.»u3tin Plains, the Willcox Playa, Great Salt Lake Desert, and the Texas
High Plains. Some rcmtiol on the fossil pollen record
can be gained from lliC nicpdeni pollen rain of "natural" plant communities in I he southwest. Despite formidable problems of lon.^-ili>tance transport of certain
pollen types it appear^ ||;a1 the major vegetation
zones have thc'ir O\MI iliM M(1]\e local pollen pool,