Volume 22, numéro 2, august 1986

EN :

Several leneoldal arorthosltlc bodies of probable Precaabrian aga, are swosed In northern Cape Breton Island within a central fault-banded block of quartzofeldspathlc (pelsses. One of these, the Red River anorthoslts coaplex Cell ka long and up to 1 ka Hide) ranges free anorthoslte to anorthositlc gabbro with hltfi Aljpa and Sr contents and large positive Eu anoaalles resulting aalnly froa plagloolase aocuailatlon.

Following an episode of polyphase deforaatlon and aaphlbollte facles aetaaorphlsa, a aonzodlorite-gabbro body of unknown age was Intruded Into both the anorthoslte and Its host rocks. The gsochealstry of this Intrusion Indicates that It Is calc-alkallne. Granite sheets, Intrusive Into the aonzodlorlte-gabbro body, do not appear to be coaagaatlc based upon the trace eleeent chealstry. These sheets aay be correlated with granitic plutons in the Cape North area which have been dated at 330 ±23 to.

FR :

Plualeura aas&es anorthosltlquss, vralsaablableaent d'age precaabrien, affleurent de aanlere lentloulaire eu sein d'un aaas central de gneiss quartzofeldspathlque, borde par des failles, dans la nord m I'tte 0X1 Cap-Breton. Paral cellea-ei, le coapiexe d'anorthoslte de Red River (d'environ 11 ka da longueur et Jusqu'a 1 ka de largsur) s'etage des anorthosltes aux gabbros anorthosltlques, aontre de haute contenus en AI2P3 et Sr et a fouml des anoaalles 6levees en Eu resultant prlnclpalament de I'acouBulatlon des plagloclasee.

Aprte un episode de deforaatlon potyphasee et adtaaorphlsae au facles aaphibollte, un corps de Bcmzonlte et gabbro d'age Incomu e'est Introdult tant dans I 'anorthoslte que dans ses encalssants. la geochlile de cette Intrusion trahft urn nature calco-alcallne. La chlile des eleaents en traces tend a nler le coaagntlsae des granites en nappe Intruelfs dans le corps de nonzodlorlte-gabbro. Ceux-cl s'apparentent plutdt aux plutons granltlques dans la region de Cape North qui sent dates a 330 ±23 Ma.

EN :

Two Rb-Sr Hhole rock Isochrons have been obtained froi plutons In the Cobequld Highlands of Nova Scotia: the Debert River and Hart Lake-Byers Lake Plutons. The undeforied, info I lated Debert River Pluton yielded an age of 596± 70 Ma and an Initial ^Sr/^Sr ratio of 0.7059 ± 0.0007. This age places an upper age I lilt on the detonation recorded In the Fol ly River Schist (youngest unit of the Bass River Coaplex), the d I or I tic Frog Lake Pluton, and the sedlaerttary rocks iMedlately north and east of the Debert River Pluton.

The Hart Lake-Byers Lake Pluton yielded anageof348±5Maandan Initial ^Sr/^Sr ratio of 0.7046 ± 0.0008. The slii I larlty of this age to that of the adjacent felslc vol can I cs of the Byers Brook For nation suggests that they are ccaagntlc and confine that a Carboniferous igjieous event fons an Inportant part of the geological history of the Cobequld Highlands. The Initial ^Sr/^r ratio and the blotite-hornblende content of the two granites suggest a eaflc Igneous loner crustal source or possible untie component for the eapa.

FR :

Les plutons de Debert River et Hart Lake-Byers Lake dans les writs Cobequld en Nouvel le-Ecosse ont llvre deux isochrones Rb-Sr de roche globale. Nl deforae nl folle, le pluton de Debert River a dome un age de 596± 70 Ma et un rapport 87Sr/88Sr Initial de 0.7059 ± 0.0007. Cecl place une llilte superleure sur rage de la deforntlon enreglstree dans le schlste de Folly River (I'unlte la plus jeune du cxaplexe de Bass River), le pluton diorltique de Frog Lake et dans les roches sedleentalres Jouxtant le pluton de Debert River au nord et a Test.

Le pluton de Hart Lake-Byers Lake a produit unftgede348±5Maetun rapport isotopique ^Sr/^Sr Initial de 0.7046 + 0.008. Cet age, siillalre a ceux des volcanltes felslques adjacentes de la formation de Byers Brook, suggere qu'lis sent comagnatlques, slgne evident qu'un episode igne carbon I fere forme I'm des falts lajeurs de I'hlstolre geologique des eonts Cobequld. Le rapport 87Sr/86Sr initial et la teneur en blot Ite et hornbIende de ces deux granites suggerent une genese crustale profonde du lapa avec une possible contribution nantelllque.

EN :

Several new localities of the trace fossil, 01 pi Ichnites, have been found In the Perao-Carbonlferous strata of northern Nova Scotia. The tral Is at Cape John, Pictou County, Nova Scotia are the largest and the youngest (Early Pen Ian) record to date of this Ichnogenus attributed to myrlapods. At the Saith Point locality the trails are nuaerous, mil preserved and have a turning configuration. Poorly preserved trails are also found near Pugwsh, Carter land County, Nova Scotia. The trails at Smith Point and Pugnaeh are late Nestpnallan In age. These trails are attributed to the giant Carboniferous myrlapod, trthropleur&.

FR :

Les strates pern-caroonlferes du Nord de la Nouvelle-Ecosse ont llvre plusleurs nouveaux glsennts de la trace fosslle Olplictoltes. Les traces de Cape John, dans le carte de Pictou en Nouvelle-Ecosse, sont les plus larges et les plus Jeunes (Eopenlen) comes a ce jour pour cet Ichnogenre que Ton attrlbue aux lyrlapodes. A la local IW de Silth Point, les Ichnites sont nortreuses, blen preservees et lontrent des trajets en vlrage. On a aussl dteouvert des traces ml preservees pres de Pugnash, dans le coatd de Cuaberland en Nouvel le-Ecosse. Les pistes de Silth Point et de Pugwash sont d'age tardimstphal I en. On attrlbue ces pistes a Artnrop/eura, un lyrlapode geant du Carbon I fere.

EN :

Rb-Sr i sot op I c data is presented for three suites of Ip^eous rocks: the Fourchu Group; volcanic rocks from Ingonlsh Island; and the Gulch Brook pluton. Results froi the Late Precambrlan metavolcanic rocks of the Fourchu Group show considerable scatter due to varying degrees of resetting of the Rb-Sr system. Seven of the elp^t sables yield an age of 407 ± 46 Ma which is be I leved to reflect the effects of the Acadian Orogeny in this area. A two-point whole-rock Isochron from the two freshest samples yield a c. 640 Ma age which could approximate the extrusive age. The redistribution of strontlui and rubldlui Isotopes suggests that the Initial ^Sr/^r ratios In the range 0.703-0.705 should be viewed with caution.

A Hhole-rock Rb-Sr isochron for volcanic rocks froe Ingonlsh Island yield an age of 412 ± 15 Ma, Interpreted to closely date the tlie of extrusion and crystallization. An Initial ^Sr/^Sr ratio of 0.706 suggests the lower crust as one possible source region.

The 413 ± 10 Ma Rb-Sr whole-rock Isochron obtained froi samples of the weakly foliated Gulch Brook pluton In northern Cape Breton Island probably represents the age of crystallization. Micas, vtilch define the weak foliation In the pluton, have previously yielded a Rb-Sr mineral Isochron of 320 Ma or Individually calculated ages of 363 Ma for muscovlte and 350 Ma for blotite (Cormier, 1980; written con. 1984) and are believed to represent resetting by a later therial event during the Late Devonian-Early Carboniferous. The Initial ^Sr/^r ratio of 0.7045 ± 0.0004 suggests a lower crustal source for the magma, possibly with a mantle component as wall. The similarity of the ages and Initial ^Sr/B^Sr ratios of the Ingonlsh Island volcanic rocks and the Gulch Brook Pluton suggest that they nay be volcanlc/subvolcanlc equivalents of one another.

FR :

On presents les signatures Isotoplques Rb-Sr de trols series de roches Igiees: le groupe de Fourchu, des volcanltes de I'fle d'Ingonlsh et le pluton de Gulch Brook. L'analyse des metavolcanltes tardlprecanbrlemes du groupe de Fourchu montre une tres grande dispersion des valours imputable au reajustement a divers degres du system Rb-Sr. Sept des hult echanti I Ions ont dome un age de 407 ± 46 Ma qui sewble tradulre les effets de I'orogenie acadleme dans ce secteur. Un Isochrone de roche globale a deux points, provenant des deux echanti I Ions les wo Ins a I teres, a prodult un age autour de 640 Ma qui pourrait approxlmer I'age de I'epanchement. La redistribution des isotopes de strontium et rubidium rend dlscutables les rapports ^Sr/^r Inltlaux aux environs de 0.703-0.705.

Un Isochrone Rb-Sr de roche globale pour les volcanltes de I'tie d'Ingonlsh a rendu un age de 412 ± 15 Ma qui correspondralt de tres pres au temps de I'extrusion et la cristalllzatlon. Le rapport wSr/*%r Initial de 0.706 evoque une genese crustale profonde.

Des echantiI Ions provenant du pluton tres peu folie de Gulch Brook, dans I'fle du Cap-Breton septentrionale, ont prodult un Isochrone Rb-Sr de roche globale de 413 ± 10 Ma qui date probablement I'age de sa cristalllzatlon. Une etude anterleure des micas (qui imprlment au pluton sa faible foliation) a deja dome un Isochrons Rb-Sr de ilneral de 320 Ma ou des Ages calcules de facer Individual re de 363 Ma pour la nuscovlte et 350 Ha pour la blotIte (Confer, 1980; com. ecrlte, 1984). On pense y deviner un reajustewnt lie a un episode theraique ulterleur tardldevonlen ou eocarbonifere. Le rapport ^Sr/^Sr Initial de 0.7045 ± 0.0004 suggere we participation de la create continentals inferleure avec une possible contribution aantellique. La slillltude des ages et des rapports ^Sr/^r Inltlaux des volcanltes de I'tie d'lngonlsh a Ins I que du pluton da Gulch Brook nous Invite a conslderer leur consangulnlte.

EN :

The 1986 Colloquium of the Atlantic Geosclence Society was held at the Wandlyn Inn, Amherst, Nova Scotia on January 17-18, 1986. The theme of the Colloquium was, "Current Research In the Atlantic Provinces." One of the highlights was the Avalon Workshop, which was held on the Friday. The workshop, organized by Sandra Barr, attracted nine papers, most of which will be published in subsequent Issues of Maritime Sediments and Atlantic Geology. At the regular sessions - on the Friday evening and all day Saturday - there were 24 oral presentations and 18 poster presentations. The quality of the papers was generally of a high standard and the subsequent discussions were Interesting and Informative. The biennial Rupert MacNell award for the best student paper was awarded to Dwanne Beattle of Dalhousle University for his paper, "Results of a gravity survey In Oarvell Bay Sabah (N. Borneo)."

The meet Ing was enthusIastIca11y supported by about 125 part i cI pants, representing the federal and provincial governments, Industry and academia. The colloqulm was organized by Lalng Ferguson with the able support from Brenda Webb. Members of the Gesner Geology Society of Mount Allison University provided assistance on the Friday and Saturday, January 17-18.

On behalf of the Atlantic Geosclence Society, we would like to thank Laing for running such a successful and enjoyable colloquium. In the following pages we publish the abstracts of papers presented at the meeting. The diversity of topics and the results Is an Indication of the vitality and depth of geological research In Atlantic Canada In the next decade.